98 Fun Facts About Endocrine System

Endocrine glands release their hormones directly into what?

The bloodstream: endocrine glands have no ducts, so their hormones travel in the blood to reach target organs far away.

Which organs make most of a woman's estrogen before menopause?

Ovaries: as their hormone output winds down at menopause, estrogen falls and bone loss speeds up, raising osteoporosis risk.

Which medical specialty treats diabetes, thyroid disorders and other hormone diseases?

Endocrinology: an early landmark came in 1849, when Arnold Berthold showed that transplanted testes restored castrated roosters' male traits.

Which of these hormones is secreted by the thyroid?

Thyroxine: it helps set the body's metabolic rate, so too little of it leaves people tired, cold and gaining weight.

Which hormone does the pineal gland secrete?

Melatonin: the gland releases the most in darkness, and light exposure cuts its production, which is how it tracks night and day.

Glands that signal each other in sequence are often called what?

An axis: in the HPA axis, cortisol from the adrenal glands inhibits the hypothalamus and pituitary that triggered its release.

Which hormone does the kidney secrete to stimulate red blood cell production?

Erythropoietin: synthetic EPO was among the drugs in the doping that cost Lance Armstrong his seven Tour de France titles.

Which of these is an exocrine gland rather than an endocrine one?

Salivary: mumps typically swells the parotids, the largest salivary glands, which pour saliva into the mouth through a duct.

The pituitary gland is divided into which two main parts?

Anterior and posterior: the posterior lobe makes no hormones of its own, only storing and releasing ones made in the hypothalamus.

Which posterior pituitary hormone helps the body retain water?

ADH: alcohol blocks its release, which is why drinking makes the kidneys let more water out as urine.

Which hormone induces uterine contractions and stimulates lactation?

Oxytocin: each contraction triggers the release of more of it, a feedback loop that makes labor contractions stronger and more frequent.

The parathyroid glands release their hormone in response to low levels of what?

Calcium: injury to the parathyroids during thyroid surgery is the most common cause of too little of their hormone, and the low calcium brings on muscle spasms.

Which pancreatic cells produce glucagon?

Alpha: when glucose runs low, their glucagon makes the liver break stored glycogen back down into glucose and release it.

Which autoimmune disease destroys the pancreas's insulin-making cells?

Type 1 diabetes: with those cells gone the body can no longer make its own insulin, so patients depend on insulin injections or a pump to survive.

In the pancreas, what do the acini secrete?

Digestive enzymes: the acini release them in an inactive form, and pancreatitis strikes when they switch on early and start digesting the pancreas itself.

What do the pancreatic delta cells produce?

Somatostatin: it works as a brake on its neighbors in the pancreas, holding back the release of both insulin and glucagon.

Which disease is caused by hypersecretion of ACTH from a pituitary adenoma?

Cushing's: the extra ACTH drives the adrenals to overproduce cortisol, which rounds the face and builds a fatty hump between the shoulders.

Which disease results from too little cortisol due to adrenal insufficiency?

Addison's: its main danger is an adrenal crisis, a sudden collapse with vomiting and fainting that can bring shock and death if untreated.

Which disease makes the thyroid overactive, flooding the body with its hormones?

Graves': the same autoimmune attack can inflame the muscles and fat around the eyes, which is why some patients' eyes bulge.

Which type of endocrine disease points to a problem with the pituitary gland?

Secondary: the thyroid itself can be healthy, but a failing pituitary stops sending the TSH that switches it on, so the gland goes quiet.

What does a hormone bind to in a target cell to change its function?

A receptor protein: a hormone acts only on cells whose receptors fit it, like a key in a lock, so it can reach every tissue yet change only its targets.

Signaling in which a cell releases a signal that acts only on nearby cells is called what?

Paracrine: the signal is quickly taken up, broken down or trapped close to where it was released, so it acts locally instead of spreading through the body.

The word 'hormone' comes from a Greek word meaning what?

Setting in motion: in 1959 two scientists blended it with Greek 'to carry' to coin 'pheromone', a chemical signal that passes between animals.

Who coined the word 'hormone' in 1905?

Ernest Starling: a 1903 experiment on a dog by him and Bayliss sparked the Brown Dog affair, a row over animal testing that led to riots in London.

Which hormone did two London physiologists discover in 1902 while testing whether nerves control the pancreas?

Secretin: cutting the nerves did not stop the pancreas responding to acid in the gut, showing that a chemical messenger could carry the signal.

Where in the body are the S cells whose hormone makes the pancreas release bicarbonate?

The duodenum: its S cells respond to acid arriving from the stomach, and the bicarbonate they trigger keeps that acid from damaging the small intestine.

Insulin's name comes from the Latin word for what?

Island: the name was coined for the hormone of the pancreas's islets years before anyone managed to isolate it.

Which two researchers isolated insulin from dog pancreas in Toronto in 1921?

Banting and Best: with dog surgery too slow to supply enough extract, Banting turned to the pancreases of fetal calves.

Who worked out the amino acid sequence of insulin?

Frederick Sanger: he gave the exact order of amino acids in both of insulin's chains, backing the idea that a protein's sequence sets its properties.

Home pregnancy tests work by detecting which hormone in urine?

hCG: the placenta starts making it once a fertilized egg attaches to the uterus wall.

Who received the first insulin injection, in Toronto in January 1922?

Leonard Thompson: his first impure dose caused an allergic reaction, but purified injections days later rapidly improved his health.

Which German medical student first described the insulin-making cell clusters of the pancreas, in 1869?

Paul Langerhans: he described the clusters without knowing what they did, and only decades later were they tied to the hormone that controls blood sugar.

The thyroid is usually described as having what shape?

Butterfly: its two wings straddle the windpipe and rise when you swallow, which is why doctors ask patients to swallow while feeling the gland.

What is the most common cause of hypothyroidism worldwide?

Iodine deficiency: that is why table salt is sold 'iodized', with a little iodine added to prevent it.

Which hormone is made by the thyroid's parafollicular cells rather than its follicular cells?

Calcitonin: a cancer of these cells, medullary thyroid cancer, can raise its level, so doctors use calcitonin tests to spot the tumor coming back.

What is an enlargement of the thyroid gland called?

Goitre: a very large one can press on the windpipe and food pipe, making it hard to breathe or swallow.

Which fat-cell hormone signals the brain about the body's stored energy?

Leptin: people with obesity usually have high levels of it, but the brain responds less to the signal, a state called leptin resistance.

Where are the adrenal glands located?

Above the kidneys: a rare tumor in one of them can release too much adrenaline, driving blood pressure dangerously high.

Drugs like Ozempic work by mimicking which hormone released by the gut?

GLP-1: the body's own hormone breaks down within about two minutes, so semaglutide is modified to last about a week, allowing one shot a week.

Which adrenal hormone tells the kidneys to hold on to sodium?

Aldosterone: a benign adrenal tumor that overproduces it is a common cause of high blood pressure in middle age.

What is cortisol called when it is used as a medication?

Hydrocortisone: low-strength hydrocortisone creams are sold without a prescription to calm itchy, inflamed skin.

Adrenaline plays an essential role in which bodily response?

Fight-or-flight: adrenaline's power to relax the airways and tighten blood vessels also makes it the emergency shot for severe allergic reactions.

Which Japanese chemist patented a purified adrenal extract, trademarked 'Adrenalin', in 1901?

Jōkichi Takamine: he also helped arrange Tokyo's 1912 gift of the cherry trees planted around Washington, D.C.'s Tidal Basin.

Which philosopher called the pineal gland the 'principal seat of the soul'?

René Descartes: he chose it because it was the only part of the brain he could find that was single rather than paired, like the soul.

The pineal gland's main hormone was first isolated from the glands of which animal?

Cows: Aaron Lerner's Yale team hoped a pineal substance could treat skin diseases, so they extracted it from cow pineal glands.

Growth hormone is secreted by somatotropic cells in which gland?

Anterior pituitary: before lab-made growth hormone arrived in 1985, patients got hormone taken from cadavers' pituitaries, which spread Creutzfeldt–Jakob disease to some.

Roughly how large is the brain's master endocrine regulator, below the thalamus?

An almond: it works as the body's thermostat, and an infection can make it reset the target temperature higher, which is what causes a fever.

In which organ do T cells mature?

Thymus: by puberty it has made the T cells a person needs, and afterward it slowly shrinks and is replaced by fat.

Which footballer with a childhood growth hormone deficiency was offered a Barcelona contract written on a paper napkin?

Lionel Messi was diagnosed at 10 and began hormone therapy at 11. His father's health insurance covered only two years of the treatment, which he finished at 14.

Which man, the tallest person in recorded history, kept growing as an adult because of an enlarged pituitary gland?

Robert Wadlow stood 8 ft 11 in when doctors measured him 18 days before his death at 22. His pituitary condition had been diagnosed when he was twelve.

Which US president's 1947 diagnosis of adrenal insufficiency in London was revealed only years after his death?

John F. Kennedy was 30 and in his first term in Congress when he was diagnosed. As president he took injected and ingested corticosteroids for the condition.

Anabolic steroids, the muscle-building drugs banned in most sports, are synthetic variants of which hormone?

Testosterone is the main male sex hormone, and its synthetic relatives are used by athletes to add muscle size and strength. The International Olympic Committee put them on its banned list in the mid-1970s.

The menopause drug Premarin, on sale since the 1940s, is made from the urine of which pregnant animals?

Horses supply it: the brand name Premarin is a contraction of 'pregnant mares' urine'. It was first marketed in Canada in 1941 and in the United States a year later.

The Latin word 'mellitus' in diabetes mellitus describes patients' urine as sweetened with which food?

Honey is the root: mellitus means honey-sweet, a nod to the sugar that spills into the urine. The word diabetes itself comes from the Greek for a siphon.

For what price did insulin's discoverers assign their patent to the University of Toronto in 1923?

$1 was a token payment, completed on 15 January 1923. Two of the team had been reluctant to patent the process at all, on grounds of medical ethics.

Which natural painkillers, stored in the pituitary gland, were named as the body's own version of morphine?

Endorphins is a contraction of 'endogenous morphine'. In 1976 three of them were sequenced from the pituitary glands of camels.

Under which official US name does adrenaline fill the auto-injectors carried by people with severe allergies?

Epinephrine was the name John Abel coined for his own adrenal extract, and it became the American generic name because Adrenalin was a registered trademark there. It is the drug in the EpiPen.

Which brain region links the nervous system to the endocrine system and controls body temperature, hunger and thirst?

The hypothalamus does this through the pituitary gland. It also sets the body's target temperature, and every fever comes from a raised setting there.

Which chemical signals, named in 1959, do animals secrete to trigger a social response in others of their own species?

Pheromones got their name from the Greek for 'I carry' plus the word hormone. Aphids release one when attacked that makes their neighbours flee.

Which control mechanism, the kind a home thermostat uses, keeps most hormone levels within their normal range?

Negative feedback governs most endocrine hormones: when the last hormone in a chain builds up, the gland that started the chain senses the excess and cuts its own output.

Which word did Walter Cannon coin in 1926 for the body's steady internal state, which hormones help maintain?

Homeostasis built on an idea from the French physiologist Claude Bernard, who had described the regulation of the body's internal environment in 1849.

Thyroid hormones act on almost every tissue in the body, chiefly by setting the pace of which process?

Metabolism is their main lever: thyroid hormones raise the basal metabolic rate. Adolf Magnus-Levy demonstrated the gland's role in 1895.

The thyroid gland sits in the front of the neck just below which landmark of the throat?

The Adam's apple sits just above it. The thyroid is attached to the cartilages of the voice box, so it moves up and down each time a person swallows.

The stress hormone cortisol follows a daily cycle in humans, with blood levels running highest at which time?

Early morning is the peak, just before or at the time of waking. Cortisol is also released in response to stress and to low blood sugar.

The body releases its largest and most predictable daily pulse of growth hormone during which activity?

Deep sleep brings the biggest surge, about an hour after a person nods off. Nearly fifty percent of growth hormone secretion happens in the two deepest stages of sleep.

Steroid hormones such as cortisol and estrogen are all built from which molecule, better known for clogging arteries?

Cholesterol is the precursor to all steroid hormones, which the body makes from it mainly in the gonads and the adrenal glands.

Which estrogen-mimicking plastics chemical was banned from baby bottles in the US, Canada and the EU?

BPA was tested as an artificial estrogen in the early 1930s by the British biochemist Edward Charles Dodds. Its largest single use is in making polycarbonate plastic.

After a carbohydrate meal, insulin prompts the liver to store surplus glucose as which branched molecule?

Glycogen chains keep growing for as long as insulin and glucose both stay plentiful. In humans it is stored mainly in the liver and in skeletal muscle.

The A1c test shows a three-month blood sugar average by measuring glucose attached to which protein?

Hemoglobin picks up more glucose the higher blood sugar runs. The test reads as a three-month average because a red blood cell lives for three to four months.

In diabetic ketoacidosis the body burns fat for want of insulin, giving the breath a fruity smell of which chemical?

Acetone, the solvent in many nail polish removers, is one of the ketone bodies the liver produces when it is forced to burn fatty acids.

Cortisone earned a 1950 Nobel Prize after large injected doses proved effective against severe cases of which disease?

Rheumatoid arthritis was the test case for Philip Hench, who shared the prize with Edward Kendall and Tadeusz Reichstein for their work on the hormones of the adrenal cortex.

Chemist Russell Marker founded Mexico's steroid industry in the 1940s by making progesterone from which wild plants?

Yams gave Marker a practical way to make progesterone. Syntex, the company he formed in 1944, later synthesised norethisterone, a hormone used in early contraceptive pills.

The parathyroid glands were first described by Victorian anatomist Richard Owen, not in a human but in which animal?

An Indian rhinoceros gave anatomy its first look at the glands. They were not found in humans until 1880, by the Swedish medical student Ivar Sandström.

Which salamander keeps its gills for life but can be pushed through metamorphosis by a dose of thyroid hormone?

Axolotl adults never build up enough thyroid hormone of their own to trigger the change, so they stay in the water and breed while still looking like larvae.

Which temporary organ acts as an endocrine gland during pregnancy, releasing the hormone that pregnancy tests look for?

The placenta begins developing shortly after implantation. The first hormone it releases prompts the corpus luteum to step up its output of progesterone.

The pituitary gland takes its name from the Latin word for which bodily fluid, which it was once thought to deliver?

Mucus, or phlegm, is what the Latin word pituita meant. The gland got the name because it was believed to channel the stuff to the nose.

The word 'gland' traces back to the Latin 'glans', which was the name of which nut?

Acorn is the root meaning. Latin glans gave the diminutive glandula, a word the Romans used for the glands of the throat and the tonsils.

The adrenal cortex, the outer and largest part of the gland, is named from the Latin for which part of a tree?

Bark is what cortex meant in Latin. English borrowed the word in the 1650s for any outer structure that resembles bark or rind.

The name 'thyroid', given in the 1600s, comes from a Greek word describing the shape of which piece of armor?

Shield is the meaning: the Greek thyreos was an oblong, door-shaped shield, and that word in turn grew out of thyra, the Greek for a door.

Adrenaline is secreted by which innermost part of the adrenal gland, whose Latin name literally means 'marrow'?

The medulla is built from chromaffin cells, which are modified nerve cells: nerve fibres of the sympathetic system run to them directly from the central nervous system.

Which pituitary hormone enables mothers to make milk, and in pigeons controls the 'crop milk' fed to chicks?

Prolactin fills the breast with milk between feeds but does not eject it. The let-down reflex is the work of a second hormone released by suckling.

A sharp mid-cycle surge of which pituitary signal triggers ovulation and is what home ovulation kits detect?

Luteinizing hormone also drives what follows: the development of the corpus luteum from the emptied follicle. The kits pick up the surge in urine.

Which stage of life begins when the brain starts releasing strong pulses of the hormone GnRH?

Puberty follows as those pulses drive a rise in sex hormones, and it can even be set off artificially by giving pulses of GnRH. Why the brain's own pulses pick up when they do is still not settled.

Kisspeptin, a brain peptide that prompts the release of GnRH, is made by a gene named after which company's chocolates?

Hershey, Pennsylvania, is where the gene was found in 1996, so the lab named it KISS1 after the town's famous Hershey's Kisses.

Before a recombinant version arrived in 1985, growth hormone for deficient children was extracted from which source?

Human cadavers supplied the pituitary glands. The product was pulled from the market in 1985 after some recipients developed Creutzfeldt–Jakob disease ten to fifteen years later.

Humulin, in 1982 the first drug made by inserting human DNA into a host cell, is insulin produced by which organism?

E. coli was the host cell. Genentech developed the technique but did not market the drug itself, leaving that to Eli Lilly.

Which X-ray crystallographer solved the structure of insulin in 1969, some 35 years after first receiving a sample?

Dorothy Hodgkin was offered a small sample of crystalline insulin in 1934, when X-ray crystallography could not yet cope with so complex a molecule, and kept at it until it could.

In a pioneering 1849 hormone experiment, Arnold Berthold castrated which animals and then transplanted the glands back?

Roosters were his subjects: castrated birds that got a testis back in a new spot in the abdomen still grew combs and wattles, crowed and chased hens, while the rest stayed capons.

Which 72-year-old scientist told a Paris society that injecting animal gland extracts had rejuvenated him?

Charles Brown-Séquard made the fluid from the sex glands of guinea pigs and dogs. Other scientists derisively nicknamed it the Brown-Séquard Elixir.

Which scientist described the body's three-phase 'general adaptation syndrome', later renamed the stress response?

Hans Selye mapped it as an alarm phase, a stage of resistance and finally exhaustion. He also split stress into harmful 'distress' and positive 'eustress'.

Which surgeon won the 1909 Nobel Prize after cutting the death rate of thyroid removal to under one percent?

Theodor Kocher was the first surgeon ever to receive a Nobel Prize in medicine, and the first Swiss citizen to win one.

Earl Sutherland won a 1971 Nobel Prize for showing that adrenaline acts through which 'second messenger' molecule?

Cyclic AMP came out of his studies of how adrenaline and glucagon release glucose, research he began in the laboratory of the Nobel laureate Carl Cori.

Estrogen was named in 1927 from 'estrus', a word for frenzied passion whose Greek root also means which insect?

Gadfly is one sense of the Greek oistros, alongside a sting and any mad impulse. Latin borrowed it as oestrus, meaning both frenzy and the fly.

Which rare adrenaline-releasing adrenal tumour causes sudden attacks of headache, sweating and a racing heart?

Pheochromocytoma grows from the gland's chromaffin cells and releases its hormones in bursts, so its spells of flushing and sweating can be mistaken for hot flashes.

Which physicist shared the 1977 Nobel Prize for radioimmunoassay, a technique first used to measure insulin in blood?

Rosalyn Yalow and her colleague Solomon Berson refused to patent the method despite its huge commercial potential. It now measures hundreds of substances once too scarce to detect.

Which stomach hormone, whose blood levels peak just before meals, is nicknamed the 'hunger hormone'?

Ghrelin earned the nickname because it increases the drive to eat. Its levels drop back again once a meal is over.

The pituitary gland sits in a hollow of the skull whose Latin name, sella turcica, translates as what?

Turkish saddle describes the shape of the depression in the sphenoid bone. The gland rests at its lowest point, known as the seat of the saddle.

Which disorder of excess growth hormone did doctors in Japan diagnose in the wrestler André the Giant?

Acromegaly went untreated in his case, and it was likely linked to the congestive heart failure that killed him in a Paris hotel at the age of 46.