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Welcome to our Hormones page, where we delve into the intricate world of hormones, their functions, and the potential impact of imbalances or abnormal secretion. Here, you’ll find an overview of various hormones, from their roles in regulating bodily functions to the symptoms or syndromes that may arise when their balance is disrupted.

 See list of hormones and some of their related symptoms/syndromes below.


Select play to watch: Dr May’s ‘Neuroendocrine Cancer, Endocrinology and Hormones’ talk.

Select play to watch: Dr Ayuk’s ‘Hormones Q&A’ talk.

Select play to watch: Professor John Newell-Price’s ‘Hormone Syndromes and You’ talk.

Select play to watch Kym Winter’s: ‘Hormone Surges, Managing Anxiety and Riding the Waves’ talk.

Hormones and their related symptoms/syndromes





Excess or Hyper-secretion symptoms and syndromes


Protein Hormone


levels of cortisol, which released from the adrenal gland

produced by the pituitary gland to stimulate the production and release of cortisol from the cortex (outer part) of the adrenal gland

can lead to high levels of cortisol in the body, also known as Cushing syndrome.


Steroid Hormone

regulation of the salt and water balance of the body

produced in the cortex (outer part) of the adrenal gland

can cause high blood pressure, low potassium levels



increases blood pressure and exerts an antidiuretic effect

produced in the hypothalamus and is transported to the pituitary gland for release

high levels can lead to Syndrome of Inappropriate Anti-Diuretic Hormone secretion (SIADH; a type of hyponatraemia)



regulates the levels of calcium (and phosphate) in the blood – by opposing the action of parathyroid hormone

produced and released by the C-cells of the thyroid gland

calcitonin levels can be altered by changes in calcium levels – raised calcitonin itself may not lead to symptoms/syndrome -though there have been reports of  excess calcitonin leading to watery diarrhoea and facial flushing. Raised calcitonin is usually related to a problem with calcium control but may also be raised in Medullary Thyroid Carcinoma (MTC) : can be a marker for MTC – but is not a contributory factor to cancer development. It may be associated with hypercalcaemia


Adrenaline (epinephrine)

Noradrenaline (norepinephrine)


work together to prepare the body for ‘fight or flight’ response in times of stress, i.e. for vigorous and/or sudden action

produced in the medulla (central part) of the adrenal glands and in some neurons of the central nervous system

overproduction of adrenaline/noradrenaline may be caused by a tumour within the medulla (central part) of the adrenal gland called pheochromocytoma or a paraganglioma (nerves of sympathetic nervous system that run through the chest and abdomen)


Peptide hormone

slows down the emptying of food from the stomach and stimulates the production of bile in the liver as well as its release from the gall bladder.

produced by I-cells in the lining of the duodenum and is also released by some neurons in the brain.

no identified association of symptoms/syndrome with excess cholecystokinin – emerging research suggests that deficiency/levels too low may be linked with obesity.


Steroid Hormone

Stress response, metabolism, blood sugar control & immune response

produced in the cortex (outer part) of the adrenal gland

High cortisol levels can lead to Cushings syndrome – also to changes in a woman’s libido and menstrual cycle, anxiiety and depression, in both sexes, may also occur

Follicle stimulating hormone 



Luteinising hormone


Peptide hormone

FSH & LH regulate the functions of both the ovaries and testes

both are released by the pituitary gland into the bloodstream

FSH levels can rise in the approach to the menopause – but excess FSH is associated with primary ovarian failure or testicular failure  which may be seen in certain genetic/chromosomal disorders – non-neuroendocrine cancer related -conditions such as Klinefelter’s syndrome in men and Turner syndrome in women. 

Excess LH may also indicate / be associated with these genetic/chromosomal disorders – but can also be seen in PCOS and/or reduced fertility


Peptide hormone

stimulates the stomach to release gastric acid

produced by the pancreas, ’G’ cells in the lining of the stomach and upper small intestine (duodenum).

Too much gastrin hormone is associated with Zollinger-Ellison syndrome, a syndrome caused by a gastrinoma – a rare neuroendocrine tumour that can occur in the pancreas or duodenum..

However, high gastrin can also occur if the pH of the stomach is too high, – where the lining of the stomach is damaged, preventing it from releasing acid. Antacid medications – such as PPIs – taken to relieve heartburn or gastroesophageal reflux disease (GERD) can also raise gastrin levels.

NB if you have been prescribed high dose PPI for the treatment of a gastrinoma – do not stop taking PPI without medical instruction/supervision.


Peptide hormone

Breaks down glycogen to glucose – helps to control blood sugar (glucose) levels.

Pancreas (alpha cells within the islets of Langerhans)

excess glucagon may be due to a rare neuroendocrine tumour of the pancreas called a glucagonoma – and can cause diabetes mellitus, weight loss, venous thrombosis and a characteristic skin rash (NME – Necrotising or Necrolytic Migratory Erythema)

Glucagon-like peptide 1

Peptide hormone

encourages the release of insulin and holds back glucagon release

It can also reduce appetite and slow stomach emptying

small intestine, pancreas and the central nervous system


Glucose-dependent insulinotropic peptide

Peptide hormone

enhances the release of insulin following the intake of food

upper section of the small intestine from a specific type of cell known as the K cell

may be linked with diabetes and/or obesity

Growth Hormone

Peptide hormone

Stimulates growth – helps to maintain normal body structure and metabolism

anterior pituitary gland

excessive growth hormone can produce a condition known as acromegaly



has a number of functions within the body including acute allergic responses, secretion of gastric acid, smooth muscle contraction, acts as a neurotransmitter within the central nervous system and in regulating immune responses

is present in peripheral nerves and endocrine cells in addition to mast cells

there are 4 key Histamine receptors – each related to various parts of the body and functions – excess histamine can therefore result in a number of symptoms including headaches or migraines, nasal congestion or sinus issues, fatigue, insomnia, mood changes, hives, digestive issues, irregular menstrual cycle, nausea and/or  vomiting.


Protein Hormone

control of blood sugar (glucose) levels

Pancreas (beta cells within the islets of Langerhans)

excess insulin leads to abnormally low blood glucose levels (called hypoglycaemia) – it may also be associated with a rare neuroendocrine tumour called an insulinoma that occurs with an incidence of 1-4 per million population.



is associated with control of the sleep–wake cycle – circadian rhythm, and also seasonal (or circannual) rhythm

produced and released from the pineal gland occurs with a clear daily (circadian) rhythm

The amount of melatonin produced by the body, whether low or high, is not usually associated with any health problems. However, some people may take it as a sleep aid – taking too much can result in drowsiness, a reduced core body temperature, headaches and fatigue – very high levels may affect sexual function and fertility.





Steroid Hormone

acts to mature and maintain the female reproductive system

is in involved in pregnancy and childbirth

it is thought that oestrone may act as a reservoir that can be converted into oestradiol as needed

In premenopausal women, oestradiol is mostly made by the ovaries – also by the placenta in pregnant women.

is made by the placenta

is primarily produced by the ovaries as well as by adipose tissue and the adrenal glands

too much oestradiol can cause acne, constipation, loss of libido, depression, female infertility, male sexual dysfunction

Obese women can produce more oestrone from their fat tissues. Increased levels may be seen in women with breast cancer and in men undergoing treatment for testicular or prostate cancer


Peptide hormone

In women – stimulates contraction of the womb (uterus) during childbirth and lactation.

In men – it plays a role in sperm transport and production of testosterone by the testes.

It is also thought to play a role in certain aspects of human behaviour – including social bonding.

produced in the hypothalamus and is secreted into the bloodstream by the posterior pituitary gland.

it is not fully understood at present if there are any implications of having too little oxytocin in the body – though abnormal levels may have an impact on milk production in breast-feeding mothers. 

High levels have been linked to benign prostatic hyperplasia

PP (Pancreatic polypeptide)


inhibits pancreatic secretion, gall bladder activity and small bowel contraction – though its full function, in humans(!), is incompletely understood.

Pancreas (PP cells)

rarely produces hormone related symptoms or syndrome, but may be secreted alongside VIP and / or Gastrin – it can be associated with a rare neuroendocrine tumour called a PPoma.


Steroid Hormone

progesterone prepares the body for pregnancy in the event that the released egg is fertilised. If it isn’t, the production of progesterone falls and a new menstrual cycle begins

mainly secreted by the corpus luteum in the ovary during the second half of the menstrual cycle. progesterone is also produced in smaller quantities by the ovaries themselves, the adrenal glands and, during pregnancy, the placenta from about week 8-12.

abnormally raised levels of progesterone can be associated with congenital adrenal hyperplasia (associated not causative) –  but may also indicate pregnancy with one or more babies, cysts on your ovaries, molar pregnancy, a disorder affecting your adrenal glands, ovarian cancer and/or breast cancer.



is usually associated with lactation, but has numerous other functions within the body including reproduction, metabolism, regulation of the immune system & fluid balance and behaviour.

produced in the anterior pituitary gland and elsewhere including the uterus, immune cells, brain, breasts, prostate, skin and adipose tissue

too much prolactin circulating in the blood is called hyperprolactinaemia – common causes include pregnancy, medications that reduce dopamine action in the body, thyroid underactivity and benign pituitary tumours (known as prolactinomas)


Eicosanoids (fatty-acid derivative)

control processes such as inflammation, blood flow, the formation of blood clots and the induction of labour.

prostaglandins are produced at the site where they are needed so can be made by nearly all cells

High levels of prostaglandins are usually produced in response to injury or infection and can cause inflammation.

Excess, prolonged release may lead to unwanted inflammation in the body such as arthritis and/or painful menstruation with heavy bleeding.

PTH (para-thyroid hormone)

Peptide hormone

regulates calcium levels in the blood – through its actions on the kidneys, bones and intestine

parathyroid glands

too much parathyroid hormone causes raised calcium levels in the blood (hypercalcaemia) and this is referred to as primary hyperparathyroidism

PTHrP (Parathyroid Hormone-Related Peptide)

Peptide hormone

as PTH – also smooth muscle relaxation and cell development

parathyroid glands

excess PTHrP is a common cause of cancer-related hypercalcaemia ( however PTHrP related hypercalcaemia tends to have suppressed/low PTH)



affects many aspects of how the gut functions including how fast food moves through your system (motility), how much fluid, such as mucus, is secreted in your intestines and how sensitive your intestines are to sensations like pain and fullness from eating. It is derived from tryptophan – an essential amino-acid that comes from dietary intake.

approx 90% of serotonin is located in the GI tract, where it regulates intestinal function, 8% is found in platelets and 1-2% in the brain/CNS (central nervous system). Serotonin is also a precursor to melatonin

excess serotonin is associated with Carcinoid Syndrome,  Carcinoid Heart Disease and / or Mesenteric Fibrosis in people with Neuroendocrine Cancer (predominantly small bowel – also lung & ovarian primaries and those with liver and/or peritoneal secondary disease {metastasies})


Peptide hormone

regulates numerous bodily functions : it inhibits the secretion of other hormones, the activity of the gastrointestinal tract and the rapid reproduction of normal and tumour cells.

produced by many tissues in the body, principally in the nervous and digestive systems

excess secretion may be caused by a rare neuroendocrine tumour called a ‘somatostatinoma’ – symptoms may include diabetes, gallstones, steatorrhoea and diarrhoea.

NB Chemically altered equivalents (analogues) of somatostatin (SSAs)  can be used as a medical therapy to control excess hormone secretion and/or neuroendocrine tumour (NET not NEC) growth


Steroid Hormone

is responsible for many of the physical characteristics specific to adult males. It plays a key role in reproduction and the maintenance of bone and muscle strength

produced by the testes and ovaries, with small quantities being produced by the adrenal glands in both sexes

The effect excess testosterone has on the body depends on both age and sex – in children it can lead to precocious puberty and may result in infertility.

In women – it has been associated with PCOS – and increased levels can cause acne, body and facial hair and deepening of the voice

In men – it has been associated with mood changes, irritability, but may also have other health consequences such as lowered sperm count, sexual dysfunction, heart and liver problems, acne, insomnia, sleep apnoea. . .

Thyroid Stimulating Hormone

Peptide hormone

controls production of the thyroid hormones, thyroxine and triiodothyronine, by the thyroid gland

is produced and released into the bloodstream by the pituitary gland

excess TSH can lead to an underactive thyroid gland or hypothyroidism.



plays vital roles in digestion, heart and muscle function, brain development and maintenance of bones

it is secreted into the bloodstream by the thyroid gland

too much thyroxine is known as thyrotoxicosis may be caused by overactivity of the thyroid gland (hyperthyroidism), as in Graves’ disease, inflammation or a benign (non-cancerous) nodule or growth.

too little thyroxine is known as hypothyroidism.



alongside thyroxine, triiodothyronine plays vital roles in digestion. heart and muscle function, brain development and bone maintenance.

Approximately 20% of triiodothyronine is secreted into the bloodstream directly by the thyroid gland. The remaining 80% is produced from conversion of thyroxine by organs such as the liver and kidneys.

too much is known as thyrotoxicosis may be caused by overactivity of the thyroid gland (hyperthyroidism), as in Graves’ disease, inflammation or a benign (non-cancerous) nodule or growth.

too little is known as hypothyroidism.

VIP (Vaso-active Intestinal Peptide)


is a potent vasodilator, regulates smooth muscle activity, epithelial cell secretion, and blood flow in the gastrointestinal tract. It also stimulates the secretion of electrolytes and water by the intestinal mucosa.

secreted by cells throughout the intestinal tract and pancreatic islet cells.

excess VIP can be associated with a rare neuroendocrine cancer of the pancreas called a VIPoma – too much VIP can lead to WDHA syndrome : profuse watery diarrhoea, hypokalaemia, achlorhydria( reduced stomach acid), lethargy, muscular weakness, nausea, vomiting, and cramp-like abdominal pain

Vitamin D – calcitriol

Steroid Hormone

Vitamin D is actually a hormone rather than a vitamin; it is required to absorb calcium from the gut into the bloodstream, it is important for normal growth and development of bones and teeth, and may also play a role in the body’s immune system and heart health too

Vitamin D is mostly produced in the skin in response to sunlight and is also absorbed from food eaten (about 10% of vitamin D is absorbed this way) as part of a healthy balanced diet. The liver and kidneys convert vitamin D, into the active hormone, which is called calcitriol.

Vitamin D deficiency is very common – and though excess Vitamin D is incredibly rare it can be toxic – 

Importantly, toxicity almost exclusively in people who take long-term, high-dose supplements without having their blood levels monitored –

symptoms associated with excess vitamin D  are similar to and include hypercalcaemia

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