I spend a lot of time talking about the most common forms of Neuroendocrine Tumours (NETs), but what about the less well-known types? As part of my commitment to all types of NETs, I’d like to shine a light on two less common tumour types known as Pheochromocytomas and Paragangliomas – incidence rate approximately 8 per million per year. They are normally grouped together and the definitions below will confirm why. If you think it’s difficult to diagnose a mainstream NET, this particular sub-type is a real challenge.
So, let’s get definitions out of the way:
Pheochromocytomas (Pheo for short)
Pheochromocytomas are tumours of the adrenal gland that produce excess adrenaline. They arise from the central portion of the adrenal gland, which is called the adrenal medulla (the remainder of the gland is known as the cortex which performs a different role and can be associated with a different tumour type). The adrenal medulla is responsible for the normal production of adrenaline, which our body requires to help maintain blood pressure and to help cope with stressful situations. The adrenal glands are situated on top of the kidneys (i.e. there are two). Adrenaline is also called ‘epinephrine’ which is curiously one of the 5 E’s of Carcinoid Syndrome.
Paragangliomas (Para for short)
Paragangliomas are tumours that grow in cells of the ‘peripheral’ nervous system (i.e. the nerves outside the brain and spinal cord). Like Pheochromocytomas, they can release excess adrenaline. There can be confusion between the two types of tumour as Paragangliomas are often described as extra-adrenal Pheochromocytomas (i.e. a Pheo external to the adrenal gland).
Going forward, I’m going to talk about both using the single term of ‘Pheochromocytoma’ in the context of an adrenaline secreting tumour but may refer to Paraganglioma where there might be a difference other than anatomical location.
Pheochromocytomas are often referred to as the “ten percent tumour” because as a rule of thumb they do many things about ten percent of the time. However, these figures are slowly changing, so this label is gradually becoming less apparent. The following is a fairly exhaustive list of these characteristics:
A few facts about Pheochromocytomas
As much as 1 in 3 are Malignant but most have undetermined biologic potential. A recent document issued by the World Health Organisation (WHO) stated that “Paragangliomas should not be termed benign”.
Around 10% of Pheochromocytomas are Bilateral (i.e. found in both adrenal glands: 90% arise in just one of the two adrenal glands)
Around 10% are Extra-Adrenal (found within nervous tissue outside of the adrenal glands … i.e. 10% are Paragangliomas)
Around 10% are found in Children (i.e. 90% in adults)
Up to 30% are Familial potentially rising to 50% for metastatic cases and Multiple Endocrine Neoplasia (MEN) involvement.
The recurrence rate is around 16%, i.e. about 1 in 6 patients have a tumor that comes back after surgery. Tumors that come back also have the potential to be malignant. If you have pheo or para and have surgery to remove it, be sure to continue to check in with your doctor to monitor for any returning tumors.
Present with a stroke (10% of these tumours are found after the patient has a stroke)
The classic symptoms of Pheochromocytomas are those attributable to excess adrenaline production. Often these patients will have recurring episodes of sweating, headache, and a feeling of high anxiety.
Headaches (severe)(one of the classic triad, see below)
Excess sweating (generalized)(one of the classic triad, see below)
Racing heart (tachycardia and palpitations)(one of the classic triad, see below)
Anxiety and nervousness
Nervous shaking (tremors)
Pain in the lower chest or upper abdomen
Nausea (with or without vomiting)
According to the ISI Book on NETs (Woltering, Vinik, O’Dorisio, et al), Pheochromocytomas present with a classic triad of symptoms and signs: headache, palpitations and sweating. This symptom complex has a high specificity and sensitivity (>90%) for the diagnosis of Pheochromocytomas. The figure is much lower in individual symptom presentations (palpitations 50%, sweating 30%, headaches 20%). In addition to correctly diagnosing from these symptoms, Pheochromocytomas may also be found incidentally during a surgical procedure even after a diagnosis of an ‘adrenal incidentaloma’
Markers. Like serotoninsecreting tumours, adrenal secreting tumours convert the offending hormone into something which comes out in urine. In fact, this is measured by 24 hour urine test very similar to 5HIAA (with its own diet and drug restrictions). It’s known as 24-hour urinary catacholamines and metanephrines. This test is designed to measure production of the different types of adrenaline compounds that the adrenal glands make. Since the body gets rid of these hormones in the urine, we simply collect a patient’s urine for 24 hours to determine if they are over-produced. Like 5HIAA, there is also a plasma (blood draw) version of the test. According to the ISI Book on NETs, there is also an additional test called ‘Vanillylmandelic Acid (VMA). This reference also indicates the most sensitive test is plasma free total metanephrines. Also read more here.
Genetics. The familial connection with Pheo/Para is complex. Up to 13 genes have been identified including NF1, RET, VHL, SDHA, SDHB, SDHC, SDHD, SDHAF2(SDH5), TMEM127, MAXm EPAS1, FH, MDH2. Read more here ( recent update). The NIH also have a useful section –click here.
Scans. Other than the usual range of scanners, ultrasound, CT/MRI, all of which may be used to find evidence of something, the other scan of note is called MIBG. This is a nuclear scan similar in concept to the Octreotide Scan given to many NET patients (in fact some Pheo patients my get an Octreotide scan if they have somatostatin receptors). The key differences with MIBG is the liquid radioactive material mix which is called iodine-123-meta-iodobenzylguanidine or 131-meta-iodobenzylguanidine (this is where the acronym MIBG originates). Together with the markers above, the results will drive treatment. Depending on availability, the latest PET scans may also be available potentially offering greater detail and accuracy i.e. 18F-FDOPA, 18F-FDG and Ga68. Read more on scans here.
This statement and diagram was provided by Dr Mark Lewis who is an Oncologist and MEN patient. “The algorithm for working up a hyperadrenergic state is attached (and was developed by Dr. Young at Mayo Clinic). It outlines the most reliable testing for a pheo or Paraganglioma”
Additional Factors and Considerations
This is an awareness post so I’m not covering treatment options in any detail except to say that surgery if often used to remove as much tumour as possible. Somatostatin Analogues may also be used in certain scenarios in addition to other hormone suppression or symptom controlling drugs. That said, Pheo/Para patients may be interested in a PRRT trial exclusively for Pheo/Para – read more here (see section entitled – “What about Pheo/Para”)
The adrenal cortex mentioned above is actually the site for Adrenocortical Carcinoma (ACC) – this is a totally different cancer.
Pheochromocytomas are probably difficult to diagnose (you only have to look at the symptoms to see that). The differential diagnoses (i.e. potential misdiagnoses) are: hyperthyroidism, hypoglycaemia, mastocytosis, carcinoid syndrome, menopause, heart failure, arrhythmias, migraine, epilepsy, porphyria lead poisoning, panic attacks and fictitious disorders such as the use of cocaine and benzedrine.
Many Pheochromocytoma patients will also be affected by Multiple Endocrine Neoplasia (MEN), in particular MEN2 (there are some wide-ranging percentage figures online for this aspect). There can also be an association with Von Hippel-Lindau (VHL) syndrome and lesscommonly with Neurofibromatosis type 1.
Given the nature of the hormones involved with Pheochromocytomas, there is a risk of intraoperative hypertensive crises. This is similar in some ways to Carcinoid Crisis but needs careful consideration by those involved in any invasive procedure.
Newly Approved Drug – AZEDRA
On 30th July 2018, Progenics Pharmaceuticals Announces FDA Approval for AZEDRA® (iobenguane I 131) to Treat Unresectable, Locally Advanced or Metastatic Pheochromocytoma or Paraganglioma – read more by clicking here.
Pheochromocytomas are very complex involving many of the challenges found in the more abundant and common types of NETs. To underscore this statement, please see this case studywhere one patient was misdiagnosed with psychiatric problems for 13 years before being correctly diagnosed with a metastatic Pheochromocytoma.
This is an extremely basic overview offered as an awareness message about the lesser known types of NETs. I refer you to my disclaimer. If you wish to learn more about Pheochromocytomas and Paragangliomas, check out the links below.
The word ‘crisis’ has a wide range of meanings and it’s well used in the media to catch the reader’s attention. Lately, the terms ‘political crisis’, financial ‘crisis’ and ‘constitutional crisis’ appear almost daily in media headlines. In a previous life, the term ‘crisis management’ was used daily in the work I was undertaking as I went from problem to problem, dampening or putting out fires (….. that’s a metaphor!). Thinking back, my adrenaline (epinephrine), norepinephrine, and cortisol must have been very busy!
However, in the world of Neuroendocrine Tumours (NETs), ‘crisis’ has a very significant meaning and its very mention will make ears prick up. The word ‘crisis’ is normally spoken or written using the term ‘Carcinoid Crisis’ given this is the type of NET with which it has been mostly associated. However, I’ve studied and researched and it would appear that some form of ‘crisis’ might apply to other types of NETs. Perhaps this is another knock-on effect caused by the historical use of the word ‘Carcinoid’ to incorrectly refer to all NETs. In terms of ‘crisis’, maybe there should be a more generic NETs wide term? More on that later.
What is ‘Carcinoid Crisis’?
In the simplest of terms, it is a dangerous change in blood pressure, heart rate, and breathing (technical term – cardiopulmonary hemodynamic instability). On an operating table under anaesthetics or an invasive procedure such as liver embolization, this can actually be life threatening. Incidentally, this happens with many other types of conditions and it is the cause of the ‘cardiopulmonary hemodynamic instability’ that is different with NET patients. For some, it could be a life or death situation.
Why does it happen to some NET Patients?
NETs can release a variety of ‘vasoactive peptides’ (hormones) in excess (e.g. serotonin, catecholamines, histamine). Under normal circumstances, these would just present as routine syndromes which may need to be controlled in most cases with somatostatin analogue treatment (Octreotide/Lanreotide).
Excess amounts of these vasoactive substances can cause both hypertension and hypotension (high and low blood pressure respectively). In extreme cases this can lead to what is known as a (carcinoid) crisis situation. It is said by one very well-known NET expert to “not to be something which happens randomly to all patients, it is usually linked to a medical procedure of some sort when you are having anaesthesia”. Dr Eric Liu also said “Luckily it is relatively uncommon”.
How is the risk managed?
If you research this plus perhaps from your own experience, you will know there are different ideas and ‘protocols’. However, they all mostly involve some pre-procedure infusion of a somatostatin analogue (normally Octreotide) – although I’d love to hear from anyone who has had Lanreotide as an alternative. Some doctors or hospitals are known to have their own ‘protocols’ and I’ve uploaded the one from the ISI NET book page 215 (Wang, Boudreaux, O’Dorisio, Vinik, Woltering, et al). Click here. Please note this is an example rather than a recommendation as this is something the NOLA team have developed for their own centre. In all the big procedures I’ve had done in my local NET Centre, I have always been admitted the day before to receive what they describe as an ‘Octreotide Soak’.
Patients are always asking about the risk and requirements for smaller procedures such as an Endoscopy. There does not seem to common guidance on this but Dr Woltering who is always forthcoming with advice suggests 200 micrograms of Octreotide before the procedure commences.
Dental visits involving anaesthetics can also be an issue and you can see Dr Woltering’s advice in my blog about the 5 Es of Carcinoid Syndrome. Additionally there is advice for users of ‘Epi Pens’. You also need to derisk those situations.
Carcinoid Syndrome vs Carcinoid Crisis
I have seen some discussion about the difference between a severe attack of carcinoid syndrome and carcinoid crisis and it’s a really difficult area. Looking at Dr Liu’s definition, he said it was ‘usually’ linked to a procedure based scenario so I guess it could happen in a non-surgical scenario in extreme cases. Most people are effectively managed on monthly injections of Octreotide/Lanreotide but some people still need ‘rescue shots’ (top ups) where they are experiencing breakthrough symptoms. When I was symptomatic (syndromic), I would regularly flush in stressful situations but that was definitely syndrome rather than crisis. Check out my video explaining how I felt. It’s worth reading something called the 5 E’s of Carcinoid Syndrome, probably useful to other types of NETs as I’m sure there is some overlap.
What about other types of NETs
The ISI Book Link above (herefor convenience), does state “regardless of tumor type, all NETs should be pre-treated with Octreotide for protection against crisis“. I know that NET patients other than those with ‘Carcinoid Tumours’ are also treated with somatostatin analogues, as they too can be subject to the effects of excess secretion of certain vasoactive peptides. I recently read an article about a person with a Pheochromocytoma (a less common NET that comes from the chromaffin cells of the adrenal medulla and secretes catecholamines). The person had what was described as an ‘Intraoperative Hypertensive Crisis’ that appeared to be caused by her tumour type rather than the sort of incident that might occur in a standard surgery. Hypertension (high blood pressure) can be a symptom of Pheochromocytoma so you can see the problem with surgery and other procedures. An interesting issue with this type of NET is that after surgery, the patient is at risk for hypotension (low blood pressure) from venous dilation caused by the sudden withdrawal of catecholamines.
I highly suspect there are many examples from the NET world beyond the ‘carcinoid’subtype of NETs and I’ve already given you one above. I’ll update this blog as I discover other examples. In the meantime, make sure you ask your medical team about ‘crisis protection’ if you are to undergo any surgical or invasive medical procedure. Minor procedures should also be assessed.
Do we need to rename the term Carcinoid Crisis to Neuroendocrine Crisis? Probably …… let’s give it a red card!
Since my diagnosis, I seem to have been in a perpetual learning phase! What not to do, what not to eat, what not to read! However, a couple of years ago, I came across a list of ‘E’ words (5 of them) which is a handy reminder for Carcinoid Syndrome patients, particularly those whose symptoms are not under control. When I say “carcinoid syndrome” in this article, I only mean the syndrome that is caused by what was once called “Carcinoid Tumors”, i.e. mainly serotonin secreting types but include tumours which are well differentiated found in the small intestine, appendiceal, rectal, lung, and one or two other less common places.
There are many variations of this list but this is my take! I suspect some of this also applies to other types of NETs and other NET Syndromes.
On analysis of this list, it struck me that I was aware of the issues and their potential effects and I’m certain there is science to substantiate the content. These E’s are apparently the most common ‘triggers’ for Carcinoid Syndrome. Clearly, they are not going to have the same effect on every patient e.g. I have the occasional drink of ‘Ethanol’ and I always enjoy it, I go for long exhausting walks and I always feel great after. I had dental treatment without any precautions before I was aware of the risks …….. nothing happened! Before I was treated, stressful meetings at work would make me flush though! As for eating – well that’s another couple of blog’s worth! (see the Diarrhea Jigsaw and Nutrition Blog 4 – Food for Thought)
The 5 Es are, however, very important, as a severe attack of Carcinoid Syndrome symptoms could be debilitating and life-threatening and I’m fairly certain the list was compiled with this in mind. Some people are more affected by Carcinoid Syndrome and this is not necessarily related to the extent or aggressiveness of their disease. Some people just react differently. An extremely severe attack of Carcinoid Syndrome can also be known as a ‘Carcinoid Crisis’ which is very dangerous on the operating table due to the effects of anaesthetics – thus why many NET patients may be infused with somatostatin analogues (usually Octreotide) prior to and during surgery or other medical procedures. There’s a lot of excitement generated around the term ‘Carcinoid Crisis’but it is generally uncommon.
I’m not saying the 5Es should be ignored but NET Cancer is complex and most things need to be read in the correct context. What works for some may not work for others. There can also be confusion surrounding the source of symptoms, i.e. are they syndrome or something else? This is why I believe NET patients need to answer some key questions when considering the risks associated with the 5 E’s:
Are you currently syndromic? If you are, then the 5 ‘E’ list is probably very good advice but interpreting the advice in the correct context remains important.
Are your syndrome related biochemistry results normal (e.g. 5HIAA)? Normal readings (in range) tend to mean the syndrome is under control and many people who were diagnosed with a syndrome may actually be non-syndromic following treatment.
Have you had treatment or are having treatment likely to produce side effects which might be confused with Carcinoid syndrome? For example, surgery can be the long term cause of diarrhea and other issues. Despite the role of somatostatin analogues, these could also be the root cause of certain reactions.
The vagaries of this disease will no doubt throw up some exceptions and additions. There will be patients who have no syndrome but have elevated biochemistry and vice versa! Additionally, there will be patients who have had surgery and/or are being treated with somatostatin analogues but will still be syndromic in varying degrees of severity.
The so-called ‘5 Es’ are as follows:
Epinephrine: This was a new piece of information for me and I only discovered this as a potential problem when I started monitoring some of the USA Facebook forums. This does not appear to be that well-known in UK. Epinephrine (commonly known as adrenaline) is often used in dentistry mixed with a local anaesthetic. I won’t risk this, so I’ve instructed my Dentist to place a note on my record asking for epinephrine not be used (and clearly I’ll remind them each visit!). According to NET guru Dr Woltering, plain novocaine, carbocaine or plain marcaine are preferred. You should also check that your anaesthetist for any procedure you may be undergoing is aware of your carcinoid syndrome. However, the danger is not just with dentistry work. Any anaesthesia is risky. Check out my post ‘carcinoid crisis’.
For those who have standby ‘Epi Pens’, I did read the following statement on the Carcinoid Cancer Foundation website: “ …….. one exception is the administration of epinephrine in the case of an allergic anaphylactic reaction (i.e. a bee sting), so it cannot be avoided in this case, just make sure that Octreotide (Sandostatin) is also available“. This advice is also extremely relevant to Pheochromocytoma and Paraganglioma patients who may be a high risk of intraoperative hypertensive crisis.
Eating: This is very individual. Certain foods or large meals can be difficult, particularly if you have had any gastrointestinal surgeries. I keep a personal diary trying to identify things that upset my system. I try to find some balance between what I know is good for me and also what I know I enjoy. For example, I found that very large meals do not agree with my ‘new plumbing’. If I eat a lot of sweets, I’ll also suffer …..so I just eat a little – check out my blog post Chocolate – The NET Effect.
Personally speaking, I’m fairly certain the vast majority of my issues are related to my treatment (past and present) rather than being provoked by Carcinoid Syndrome, i.e. if I rush to the toilet after a meal, it’s not syndrome, it’s a reaction of my compromised digestive system. So with this in mind, I try to reduce those things but additionally strike a balance between quality of life and excessive and rigid adherence to some of the guidance out there (see below) – as I said above, interpretation and context is important. My compromised system cannot deal with big meals so I ‘graze’ most of the day and then eat a small to medium-sized meal in the evening. I’ve been doing this for 3 years and reduced my visits by 300% without any special or expensive medication.
In my blog Nutrition Blog 4 – Food for Thought, I’ve linked to authoritative sources on potential diet triggers. I’m not suggesting you cut out all of the foods on these lists (you won’t last long!). Some can indulge in those foods and some cannot. For example, chocolate and caffeine (tea/coffee) are on the lists but I eat/drink those frequently (in moderation) and have no problem. It’s a case of testing things out. I like to describe my eating as ‘The Risk Management of my Quality of Life’. By the way, no-one is suggesting that a NET patient with carcinoid syndrome (and don’t forget this is only one syndrome of many with NETs) should stop eating foods high in the offending amines or are precursors to serotonin (e.g. tryptophan). They do not make tumours grow (a myth) but just make sure you adhere to the dietary restrictions for any 5HIAA test.
Emotions: Stressful situations can cause symptoms to flare up. While it is difficult to avoid all stress (work, home, commuting, etc), it is helpful if you can manage or reduce it. Like eating, this is a very individual area. From personal experience, I know stress can exacerbate carcinoid syndrome. Before I started my treatment, I was regularly flushing in meetings at work (….. think boxing matches!). After my treatment, stress was definitely a factor causing increased bowel motility. I’ve removed a lot of stress from my life and it helps. You may need to be ruthless in managing this aspect of your illness.
Exercise: Exercise is extremely important for overall health and well-being and I know quite a lot of NET Cancer patients who exercise regularly without issues. It can, however, trigger carcinoid syndrome if you overdo it – it is, however, like eating, a very individual thing. I take the view that ‘zero’ exercise might potentially be an even higher risk. Even a walk around the garden or gardening is exercise. When I was at work, I would walk to see people rather than phone them. Sometimes I walk to town rather than drive, it all adds up! I have evidence from my own exercising regime proving in my case that exercise can reduce the knock-on effects of some of the other E’s (emotions and eating) and/or the side effects of treatment – check out my blog entitled Exercise is Medicine. Those who are syndromic and/or have other conditions to manage are probably best to take medical advice on how much exercise they need to do.
Ethanol (alcohol, liquor):Many NET patients have difficulty tolerating wine, beer and spirits (hard liquor). I was never a big drinker so for me it was easy to go almost teetotal. I do have the occasional beer but very infrequently and normally on holiday – I personally don’t get any issues with the odd beer but again this is trial and error. I really enjoy my beer when I celebrate my ‘Cancerversaries‘. Also check out my blog Alcohol – the NET Effect
I’m sure there could be a 5 A’s to 5 Z’s list of things to avoid but as I said above, this needs to be balanced with what the actual risks for you are and if you’re like me, quality of life. If you read most Facebook closed group or forums, you will always find at least one person is affected by something which affects no-one else. Please note this article is just my own appreciation of these issues and I emphasise once again that everyone has different experiences. I do, however, think it’s important to consider any secondary illnesses, effects of surgery and biochemistry results (or indeed a combination of one or more of these factors). Everything in life involves some kind of risk management and if you are totally risk averse, then you are unlikely to have much of a life (or a diet!).
It’s not easy but my daily diary helps me assess trends and work out what things upset me more than others – I can then reduce or eliminate. You need to tailor your own advice perhaps with the help of a doctor and/or dietician versed in NET Cancer. I also have some related posts on the subject of vitamin and mineral deficiencies, malabsorption and probiotics – check them out as the problems associated with these subjects could potentially look like a worsening of carcinoid syndrome and lead to unnecessary worry and unnecessary treatment.
For most, Carcinoid Syndrome can normally be controlled by the use of debulking surgery and/or somatostatin analogues (Octreotide/Lanreotide). However, there is a new drug called ‘Teloristat Ethyl’ (XERMELO) which looks like it may provide supplementary treatment for patients whose carcinoid syndrome diarrhea is not adequately controlled by somatostatin analogues. It’s an expensive drug and comes with side effects so you need to be sure it’s your syndrome causing the problem before you commit to a prescription.
Until I was diagnosed with metastatic Neuroendocrine Cancer, I didn’t have a clue about hormones – it’s one of those things you just take for granted. However, hormones are vital to human health (male and female) and it’s only when things go wrong you suddenly appreciate how important they are ……..like a lot of other things in life I suppose! The presence of over-secreting hormones (often called peptides throughout) is useful to aid diagnosis albeit it often means the tumours have metastasized. It’s also a frequent indication that the person has an associated NET syndrome.
This is a really complex area and to understand the hormone problems associated with Neuroendocrine Cancer, you need to have a basic knowledge of the endocrine and neuroendocrine systems. I’ve no intention of explaining that (!) – other than the following high level summary:
Glands in the endocrine system use the bloodstream to monitor the body’s internal environment and to communicate with each other through substances called hormones, which are released into the bloodstream. Endocrine glands include; Pituitary, Hypothalmus, Thymus, Pineal, Testes, Ovaries Thyroid, Adrenal, Parathyroid, Pancreas.
A Hormone is a chemical that is made by specialist cells, usually within an endocrine gland, and it is released into the bloodstream to send a message to another part of the body. It is often referred to as a ‘chemical messenger’. In the human body, hormones are used for two types of communication. The first is for communication between two endocrine glands, where one gland releases a hormone which stimulates another target gland to change the levels of hormones that it is releasing. The second is between an endocrine gland and a target organ, for example when the pancreas releases insulin which causes muscle and fat cells to take up glucose from the bloodstream. Hormones affect many physiological activities including growth, metabolism, appetite, puberty and fertility.
The Endocrine system. The complex interplay between the glands, hormones and other target organs is referred to as the endocrine system.
The Neuroendocrine System. The diffuse neuroendocrine system is made up of neuroendocrine cells scattered throughout the body. These cells receive neuronal input and, as a consequence of this input, release hormones to the blood. In this way they bring about an integration between the nervous system and the endocrine system (i.e. Neuroendocrine). A complex area but one example of what this means is the adrenal gland releasing adrenaline to the blood when the body prepares for the ‘fight or flight’ response in times of stress, ie, for vigorous and/or sudden action.
Hormones – the NET Effect
At least one or more hormones will be involved at various sites and even within certain syndromes, the dominant and offending hormone may differ between anatomical tumour sites. For example, NETs of the small intestine, lung or appendix (and one or two other places) may overproduce serotonin and other hormones which can cause a characteristic collection of symptoms currently called carcinoid syndrome. The key symptoms are flushing,diarrhea and general abdominal pain, loss of appetite, fast heart rate and shortness of breath and wheezing. The main symptom for me was facial flushing and this was instrumental in my eventual diagnosis. The fact that I was syndromic at the point of diagnosis made it easier to discover, albeit the trigger for the investigation was a fairly innocuous event. Other types of NETs are also affected by the overproduction of hormones including Insulinomas, Gastrinomas, Glucagonomas, VIPomas, Somatostatinomas, and others. These can cause their own syndromes and are not part of carcinoid syndrome as some organisations incorrectly state. For more on NET syndromes – Read Here.
So are hormones horrible?
Absolutely not, they are essential to the normal function of the human body. For example if you didn’t have any of the hormone Serotonin in your system, you would become extremely ill. On the other hand, if your glands start secreting too much of certain hormones, your body could become dysfunctional and in some scenarios, this situation could become life threatening. So hormones are good as long as the balance is correct. NET patients with an oversecreting tumor may be classed as “functional”.
Functional tumors make extra amounts of hormones, such as gastrin, insulin, and glucagon, that cause signs and symptoms.
Nonfunctional tumors do not make extra amounts of hormones. Signs and symptoms are caused by the tumor as it spreads and grows. Many NET patients are deemed to be “non-functioning” with normal hormone levels. It’s also accurate to say that many can move from one stage to the other.
Location Location Location
It’s accurate to say that the type and amount of hormone secretion differs between locations or sites of the functional tumor and this can also create different effects. The division of NETs into larger anatomical regions appears to differ depending on where you look but they all look something likes this:
Foregut NETs: In the respiratory tract, thymus, stomach, duodenum, and pancreas. This group mostly lack the enzyme aromatic amino decarboxylase that converts 5-HTP (5-Hydroxytryptophan – a precursor to serotonin) to serotonin (5-HT); such tumours tend to produce 5-HTP and histamine instead of serotonin. The Pancreas is a particularly prominent endocrine organ and can produce a number of different syndromes each with their associated hormone oversecretion – although many can be non-functional (at least to begin with). Lung NETs rarely produce serotonin, but may instead secrete histamine causing an ‘atypical’ carcinoid syndrome with generalized flushing, diarrhea, periorbital oedema, lacrimation and asthma. They may also produce adrenocorticotropic hormone (ATCH) or corticotropin-releasing factor (CRP), resulting in an ectopic Cushing’s syndrome. Please note the respiratory tract and thymus are not really anatomically pure ‘Foregut’ – but in NETs, grouped there for convenience.
Midgut NETs: In the small intestine, appendix, and ascending colon. For example, serotonin secreting tumors tend to be associated with carcinoid syndrome which tends to be associated with midgut NETs and this is normally the case. Many texts will also tell you that a syndrome only occurs at a metastatic stage. Both are a good rule of thumb but both are technically incorrect. For example, ovarian NETs can have a form of carcinoid syndrome without liver metastasis (tends to be described as atypical carcinoid syndrome). It’s also possible to see serotonin secreting tumors in places such as the pancreas (although what you would call that type of NET is open for debate).
Hindgut NETs (transverse, descending colon and rectum) cannot convert tryptophan to serotonin and other metabolites and therefore rarely cause carcinoid syndrome even if they metastasise to the liver.
Less Common Locations – there are quite a few less common NET locations which may involve less common hormones – some are covered below including the key glands contributing to NETs.
Unknown Primary? – One clue to finding the primary might be by isolating an offending hormone causing symptoms.
The key NET hormones
I used the example of Serotoninabove because it is the most cited problem with NET Cancer although it does tend to be most prevalent in midgut tumors. Serotonin is a monoamine neurotransmitter synthesized from Tryptophan, one of the eight essential amino acids (defined as those that cannot be made in the body and therefore must be obtained from food or supplements). About 90% of serotonin produced in the body is found in the enterochromaffin cells of the gastrointestinal (GI) tract where it is used mainly to regulate intestinal movements amongst other functions. The remainder is synthesized in the central nervous system where it mainly regulates mood, appetite, and sleep. Please note there is no transfer of serotonin across the blood-brain barrier.
Alterations in tryptophan metabolism may account for many symptoms that accompany carcinoid syndrome. Serotonin in particular is the most likely cause of many features of carcinoid syndrome as it stimulates intestinal motility and secretion and inhibits intestinal absorption. Serotonin may also stimulate fibroblast growth and fibrogenesis and may thus account for peritoneal and valvular fibrosis encountered in such tumours; serotonin, however, it is said not to be associated with flushing. The diversion of tryptophan to serotonin may lead to tryptophan deficiency as it becomes unavailable for nicotinic acid synthesis, and is associated with reduced protein synthesis and hypoalbuminaemia; this may lead to the development of pellagra (skin rash, glossitis, stomatitis, confusion/dementia).
Serotonin is also thought to be responsible for ‘right sided’ heart disease (Carcinoid Heart Disease). It is thought that high levels of serotonin in the blood stream damages the heart, leading to lesions which cause fibrosis, particularly of the heart valves. This generally affects the right side of the heart when liver metastases are present. The left side of the heart is usually not affected because the lungs can break down serotonin. Right sided heart failure symptoms include swelling (edema) in the extremities and enlargement of the heart.
Whilst serotonin can be measured directly in the blood, it’s said to be more accurate to measure 5HIAA (the output of serotonin) via blood or urine, the latter is said to be the most accurate.
Tackykinins include Substance P, Neurokinin A, Neuropeptide K and others. They are active in the enterochromaffin cells of the GI tract but can also be found in lung, appendiceal and ovarian NETs, and also in Medullary Thyroid Carcinoma and Pheochromocytomas. They are thought to be involved in flushing and diarrhea in midgut NETs. The most common tachykinin is Substance P, which is a potent vasodilator (substances which open up blood vessels). Telangiectasias are collections of tiny blood vessels which can develop superficially on the faces of people who have had NETs for several years. They are most commonly found on the nose or upper lip and are purplish in color. They are thought to be due to chronic vasodilatation.
Histamine is a hormone that is chemically similar to the hormones serotonin, epinephrine, and norepinephrine. After being made, the hormone is stored in a number of cells (e.g., mast cells, basophils, enterochromaffin cells). Normally, there is a low level of histamine circulating in the body. However (and as we all know!), the release of histamine can be triggered by an event such as an insect bite. Histamine causes the inconvenient redness, swelling and itching associated with the bite. For those with severe allergies, the sudden and more generalized release of histamine can be fatal (e.g., anaphylactic shock). Mast cell histamine has an important role in the reaction of the immune system to the presence of a compound to which the body has developed an allergy. When released from mast cells in a reaction to a material to which the immune system is allergic, the hormone causes blood vessels to increase in diameter (e.g., vasodilation) and to become more permeable to the passage of fluid across the vessel wall. These effects are apparent as a runny nose, sneezing, and watery eyes. Other symptoms can include itching, burning and swelling in the skin, headaches, plugged sinuses, stomach cramps, and diarrhea. Histamine can also be released into the lungs, where it causes the air passages to become constricted rather than dilated. This response occurs in an attempt to keep the offending allergenic particles from being inhaled. Unfortunately, this also makes breathing difficult. An example of such an effect of histamine occurs in asthma. Histamine has also been shown to function as a neurotransmitter (a chemical that facilitates the transmission of impulses from one neural cell to an adjacent neural cell).
In cases of an extreme allergic reaction, adrenaline is administered to eliminate histamine from the body. For minor allergic reactions, symptoms can sometimes be lessened by the use of antihistamines that block the binding of histamine to a receptor molecule. Histamine is thought to be involved with certain types and locations of NET, including Lung and foregut NETs where they can cause pulmonary obstruction, atypical flush and hormone syndromes.
Histamine, another amine produced by certain NETs (particularly foregut), may be associated with an atypical flushing and pruritus; increased histamine production may account for the increased frequency of duodenal ulcers observed in these tumours.
Kallikrein is a potent vasodilator and may account for the flushing and increased intestinal mobility.
Although prostaglandins are overproduced in midgut tumours, their role in the development of the symptoms of carcinoid syndrome is not well established but triggering peristalsis is mentioned in some texts.
Bradykinin acts as a blood vessel dilator. Dilation of blood vessels can lead to a rapid heartbeat (tachycardia) and a drop in blood pressure (hypotension). Dilation of blood vessels may also be partly responsible for the flushing associated with carcinoid syndrome.
Gastrin is a hormone that is produced by ‘G’ cells in the lining of the stomach and upper small intestine. During a meal, gastrin stimulates the stomach to release gastric acid. This allows the stomach to break down proteins swallowed as food and absorb certain vitamins. It also acts as a disinfectant and kills most of the bacteria that enter the stomach with food, minimising the risk of infection within the gut. Gastrin also stimulates growth of the stomach lining and increases the muscle contractions of the gut to aid digestion. Excess gastrin could indicate a NET known as a Gastric NET (stomach) or a pNET known as Gastrinoma (see pancreatic hormones below).
Calcitonin is a hormone that is produced in humans by the parafollicular cells (commonly known as C-cells) of the thyroid gland. Calcitonin is involved in helping to regulate levels of calcium and phosphate in the blood, opposing the action of parathyroid hormone. This means that it acts to reduce calcium levels in the blood. This hormone tends to involve Medullary Thyroid Carcinoma and Hyperparathyroidism in connection to those with Multiple Endocrine Neoplasia. Worth also pointing out the existence of Calcitonin Gene-Related Peptide (CGRP) which is a member of the calcitonin family of peptides and a potent vasodilator. Please note that hypothyroidism is often a side effect of NETs or treatment for NETs – please click here to read about the connection.
HPA AXIS – It’s important to note something called the HPA axis when discussing pituitary hormones as there is a natural and important connection and rhythm between the Hypothalamus, Pituitary and the Adrenal glands. However, I’m only covering the pituitary and adrenal due to their strong connection with NETs.
Adrenocorticotropic hormone (ATCH) is made in the corticotroph cells of the anterior pituitary gland. It’s production is stimulated by receiving corticotrophin releasing hormone (CRH) from the Hypothalamus. ATCH is secreted in several intermittent pulses during the day into the bloodstream and transported around the body. Like cortisol (see below), levels of ATCH are generally high in the morning when we wake up and fall throughout the day. This is called a diurnal rhythm. Once ACTH reaches the adrenal glands, it binds on to receptors causing the adrenal glands to secrete more cortisol, resulting in higher levels of cortisol in the blood. It also increases production of the chemical compounds that trigger an increase in other hormones such as adrenaline and noradrenaline. If too much is released, The effects of too much ATCH are mainly due to the increase in cortisol levels which result. Higher than normal levels of ATCH may be due to:
Cushing’s disease – this is the most common cause of increased ATCH. It is caused by a tumor in the pituitary gland (PitNET), which produces excess amounts of ATCH. (Please note, Cushing’s disease is just one of the numerous causes of Cushing’s syndrome). It is likely that a Cortisol test will also be ordered if Cushing’s is suspected.
A tumour outside the pituitary gland, producing ATCH is known as an ectopic ATCH. With NETs, this is normally a pNET, Lung/Bronchial/Pulmonary NET or Pheochromocytoma.
Adrenaline and Noradrenline
These are two separate but related hormones and neurotransmitters, known as the ‘Catecholamines’. They are produced in the medulla of the adrenal glands and in some neurons of the central nervous system. They are released into the bloodstream and serve as chemical mediators, and also convey the nerve impulses to various organs. Adrenaline has many different actions depending on the type of cells it is acting upon. However, the overall effect of adrenaline is to prepare the body for the ‘fight or flight’ response in times of stress, i.e. for vigorous and/or sudden action. Key actions of adrenaline include increasing the heart rate, increasing blood pressure, expanding the air passages of the lungs, enlarging the pupil in the eye, redistributing blood to the muscles and altering the body’s metabolism, so as to maximise blood glucose levels (primarily for the brain). A closely related hormone, noradrenaline, is released mainly from the nerve endings of the sympathetic nervous system (as well as in relatively small amounts from the adrenal medulla). There is a continuous low-level of activity of the sympathetic nervous system resulting in release of noradrenaline into the circulation, but adrenaline release is only increased at times of acute stress. These hormones are normally related to adrenal and extra adrenal NETs such as Pheochromocytoma and Paraganglioma. Like serotonin secreting tumours, adrenal secreting tumours convert the offending hormone into something which comes out in urine. In fact, this is measured (amongst other tests) by 24 hour urine test very similar to 5HIAA (with its own diet and drug restrictions). It’s known as 24-hour urinary catacholamines and metanephrines. Worth noting that adrenaline is also known as Epinephrine (one of the 5 E’s of Carcinoid Syndrome).
This is a steroid hormone, one of the glucocorticoids, made in the cortex of the adrenal glands and then released into the blood, which transports it all round the body. Almost every cell contains receptors for cortisol and so cortisol can have lots of different actions depending on which sort of cells it is acting upon. These effects include controlling the body’s blood sugar levels and thus regulating metabolism acting as an anti-inflammatory, influencing memory formation, controlling salt and water balance, influencing blood pressure. Blood levels of cortisol vary dramatically, but generally are high in the morning when we wake up, and then fall throughout the day. This is called a diurnal rhythm. In people who work at night, this pattern is reversed, so the timing of cortisol release is clearly linked to daily activity patterns. In addition, in response to stress, extra cortisol is released to help the body to respond appropriately. Too much cortisol over a prolonged period of time can lead to Cushing’s syndrome. Cortisol oversecretion can be associated with Adrenal Cortical Carcinoma (ACC) which can sometimes be grouped within the NET family.
Other hormones related to ACC include:
Androgens (e.g. Testosterone) – increased facial and body hair, particularly females. Deepened voice in females.
Estrogen – early signs of puberty in children, enlarged breast tissue in males.
Aldosterone – weight gain, high blood pressure.
Adrenal Insufficiency (Addison’s Disease) occurs when the adrenal glands do not produce enough of the hormone cortisol and in some cases, the hormone aldosterone. For this reason, the disease is sometimes called chronic adrenal insufficiency, or hypocortisolism.
Parathyroid hormone (PTH) is secreted from four parathyroid glands, which are small glands in the neck, located behind the thyroid gland. Parathyroid hormone regulates calcium levels in the blood, largely by increasing the levels when they are too low. A primary problem in the parathyroid glands, producing too much parathyroid hormone causes raised calcium levels in the blood (hypercalcaemia – primary hyperparathyroidism). You may also be offered an additional test called Parathyroid Hormone-Related Peptide (PTHrP). They would probably also measure Serum Calcium in combination with these type of tests. The parathyroid is one of the ‘3 p’ locations often connected to Multiple Endocrine Neoplasia – MEN 1
Pancreatic Hormones (Syndromes)
Pancreatic neuroendocrine tumors form in hormone-making cells of the pancreas. You may see these described as ‘Islet Cells’ or ‘Islets of Langerhans’ after the scientist who discovered them. Pancreatic NETs may also be functional or non-functional:
Functional tumors make extra amounts of hormones, such as gastrin, insulin, and glucagon, that cause signs and symptoms.
Nonfunctional tumors do not make extra amounts of hormones. Signs and symptoms are caused by the tumor as it spreads and grows.
There are different kinds of functional pancreatic NETs. Pancreatic NETs make different kinds of hormones such as gastrin, insulin, and glucagon. Functional pancreatic NETs include the following:
Gastrinoma: A tumor that forms in cells that make gastrin. Gastrin is a hormone that causes the stomach to release an acid that helps digest food. Both gastrin and stomach acid are increased by gastrinomas. When increased stomach acid, stomach ulcers, and diarrhea are caused by a tumor that makes gastrin, it is called Zollinger-Ellison syndrome. A gastrinoma usually forms in the head of the pancreas and sometimes forms in the small intestine. Most gastrinomas are malignant (cancer).
Insulinoma: A tumor that forms in cells that make insulin. Insulin is a hormone that controls the amount of glucose (sugar) in the blood. It moves glucose into the cells, where it can be used by the body for energy. Insulinomas are usually slow-growing tumors that rarely spread. An insulinoma forms in the head, body, or tail of the pancreas. Insulinomas are usually benign (not cancer).
Glucagonoma: A tumor that forms in cells that make glucagon. Glucagon is a hormone that increases the amount of glucose in the blood. It causes the liver to break down glycogen. Too much glucagon causes hyperglycemia (high blood sugar). A glucagonoma usually forms in the tail of the pancreas. Most glucagonomas are malignant (cancer).
Pancreatic Polypeptide (PPoma). A pancreatic polypeptide is a polypeptide hormone secreted by the pancreatic polypeptide (PP) cells of the islets of Langerhans in the endocrine portion of the pancreas. Its release is triggered in humans by protein-rich meals, fasting, exercise, and acute hypoglycemia and is inhibited by somatostatin and intravenous glucose. The exact biological role of pancreatic polypeptide remains uncertain. Excess PP could indicate a pNET known as PPoma.
Other types of tumors: There are other rare types of functional pancreatic NETs that make hormones, including hormones that control the balance of sugar, salt, and water in the body. These tumors include:
VIPomas, which make vasoactive intestinal peptide. VIPoma may also be called Verner-Morrison syndrome, pancreatic cholera syndrome, or the WDHA syndrome (Watery Diarrhea, Hypokalemia (low potassium)and Achlorhydria).
Somatostatinomas, which make somatostatin. Somatostatin is a hormone produced by many tissues in the body, principally in the nervous and digestive systems. It regulates a wide variety of physiological functions and inhibits the secretion of other hormones, the activity of the gastrointestinal tract and the rapid reproduction of normal and tumour cells. Somatostatin may also act as a neurotransmitter in the nervous system.
Having certain syndromes can increase the risk of pancreatic NETs.
Anything that increases your risk of getting a disease is called a risk factor. Having a risk factor does not mean that you will get cancer; not having risk factors doesn’t mean that you will not get cancer. Talk with your doctor if you think you may be at risk. Multiple endocrine neoplasia type 1 (MEN1) syndrome is a risk factor for pancreatic NETs.
Signs and symptoms of pancreatic NETs
Signs or symptoms can be caused by the growth of the tumor and/or by hormones the tumor makes or by other conditions. Some tumors may not cause signs or symptoms. Check with your doctor if you have any of these problems.
Signs and symptoms of a non-functional pancreatic NET
A non-functional pancreatic NET may grow for a long time without causing signs or symptoms. It may grow large or spread to other parts of the body before it causes signs or symptoms, such as:
A lump in the abdomen.
Pain in the abdomen or back.
Yellowing of the skin and whites of the eyes.
Signs and symptoms of a functional pancreatic NET
The signs and symptoms of a functional pancreatic NET depend on the type of hormone being made.
Too much gastrin may cause:
Stomach ulcers that keep coming back.
Pain in the abdomen, which may spread to the back. The pain may come and go and it may go away after taking an antacid.
The flow of stomach contents back into the esophagus (gastroesophageal reflux).
Too much insulin may cause:
Low blood sugar. This can cause blurred vision, headache, and feeling lightheaded, tired, weak, shaky, nervous, irritable, sweaty, confused, or hungry.
Too much glucagon may cause:
Skin rash on the face, stomach, or legs.
High blood sugar. This can cause headaches, frequent urination, dry skin and mouth, or feeling hungry, thirsty, tired, or weak.
Blood clots. Blood clots in the lung can cause shortness of breath, cough, or pain in the chest. Blood clots in the arm or leg can cause pain, swelling, warmth, or redness of the arm or leg.
Weight loss for no known reason.
Sore tongue or sores at the corners of the mouth.
Too much vasoactive intestinal peptide (VIP) may cause:
Very large amounts of watery diarrhea.
Dehydration. This can cause feeling thirsty, making less urine, dry skin and mouth, headaches, dizziness, or feeling tired.
Low potassium level in the blood. This can cause muscle weakness, aching, or cramps, numbness and tingling, frequent urination, fast heartbeat, and feeling confused or thirsty.
Cramps or pain in the abdomen.
Weight loss for no known reason.
Too much somatostatin may cause:
High blood sugar. This can cause headaches, frequent urination, dry skin and mouth, or feeling hungry, thirsty, tired, or weak.
Steatorrhea (very foul-smelling stool that floats).
Yellowing of the skin and whites of the eyes.
Weight loss for no known reason.
Too much pancreatic polypeptide may cause:
an enlarged liver.
Clearly the presenting symptoms will give doctors a clue to the oversecreting hormone (see list above). Excessive secretions or high levels of hormones and other substances can be measured in a number of ways. For example:
Well known tests for the most common types of NET include 5-Hydroxyindoleacetic Acid (5-HIAA) 24 hour urine test which is also measured by a blood draw. Note: -tumor markers can be measured simultaneously e.g. Chromogranin A (CgA) blood test and/or Pancreastatin as there can very often be a correlation between tumour mass and tumour secreting activity. CgA / Pancreastatin is a blood test which measures a protein found in many NET tumour cells. These marker tests are normally associated with tumour mass rather than tumour functionality.
By measuring the level of 5-HIAA in the urine or blood, healthcare providers can calculate the amount of serotonin in the body (5-HIAA is a by-product of serotonin). 5-HIAA test is the most common biochemical test for carcinoid syndrome or the degree of how ‘functional’ tumours are. If you’ve understood the text above, you can now see why there are dietary and drug restrictions in place prior to the test.
Pancreatic Hormone testing. There are other tests for other hormones and there is a common test which measured the main hormones seen in NETs. It may be called different things in different countries, but in UK, it’s known as a ‘Fasting Gut Hormone Profile‘.
Scratching the surface here so for a comprehensive list of marker tests for NETs, have aread here.
Treatment for Over-secreting Hormones
Of course, reducing tumour bulk through surgery and other treatment modalities, should technically reduce over-secretion (I suspect that doesn’t work for all). Other treatments may have the dual effect of reducing tumour burden and the effects of hormone oversecretions.
One of the key treatment breakthroughs for many NET cancer patients, is the use of ‘Somatostatin Analogues’ mainly branded as Octreotide (Sandostatin) or Lanreotide (Somatuline). People tend to associate these drugs with serotonin related secretions and tumours but they are in actual fact useful for many others including the pancreatic NETs listed above. Patients will normally be prescribed these drugs if they are displaying these symptoms but some people may be more avid to the drug than others and this may influence future use and dosages. This is another complex area but I’ll try to describe the importance here in basic terms. Somatostatin is a naturally occurring protein in the human body. It is an inhibitor of various hormones secreted from the endocrine system (some of which were listed above) and it binds with high affinity to the five somatostatin receptors found on secretory endocrine cells. NETs have membranes covered with receptors for somatostatin. However, the naturally occurring Somatostatin has limited clinical use due to its short half-life (<3 min). Therefore, specific somatostatin analogues (synthetic versions) have been developed that bind to tumours and block hormone release. Thus why Octreotide and Lanreotide do a good job of slowing down hormone production, including many of the gut hormones controlling emptying of the stomach and bowel. It also slows down the release of hormones made by the pancreas, including insulin and digestive enzymes – so there can be side effects including fat malabsorption.
The recent introduction of Telotristat Ethyl(XERMELO) is interesting as that inhibits a precursor to serotonin and reduces diarrhea in those patients where it is not adequately controlled by somatostatin analogues.
Other than the effects of curative or cytoreductive surgery, some NETs may have very specialist drugs for inhibiting the less common hormone types. This is not an exhaustive list.
Worth also noting that oversecreting hormones can contribute to a phenomenon known as Carcinoid Crisis – read more here. For catacholamine secreting tumors (Pheochromocytoma/Paraganglioma), this may be known as Intraoperative Hypertensive Crisis
Sorry about the long article – it’s complex and you should always consult your specialist about issues involving hormones, testing for hormones and treating any low or high scores.