50 Fun Facts About Endocrine System

Endocrine glands release their hormones directly into what?

That is the difference from exocrine glands like salivary glands, which use ducts.

Which brain region is the neural control center for the endocrine system in vertebrates?

It links the nervous system to the endocrine system through the pituitary gland just below it.

What is the study of the endocrine system and its disorders called?

It is a branch of internal medicine.

Which of these hormones is secreted by the thyroid?

Thyroxine is T4; the gland also makes T3 and calcitonin.

Which hormone does the pineal gland secrete?

The pine-cone-shaped gland sits near the center of the brain and helps set the sleep-wake cycle.

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

The hypothalamic-pituitary-adrenal axis is the classic example.

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

Synthetic versions, known as EPO, became notorious as a doping agent in endurance sport.

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

Exocrine glands have ducts or a hollow lumen; endocrine glands have no ducts.

The pituitary gland is divided into which two main parts?

The posterior lobe stores hormones made in the hypothalamus; the anterior lobe makes its own.

Which posterior pituitary hormone helps the body retain water?

Also called ADH or vasopressin, it is synthesized in the hypothalamus's supraoptic nucleus.

Which hormone induces uterine contractions and stimulates lactation?

It is sometimes nicknamed the 'cuddle hormone' for its role in bonding.

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

Parathyroid hormone acts on bone, kidneys and gut to raise blood calcium, and activates vitamin D.

Which pancreatic cells produce glucagon?

Glucagon tells the liver to release stored sugar when blood glucose runs low.

Roughly what share of pancreatic islet cells are insulin-making beta cells?

Delta cells, which make somatostatin, are only about 5% of the islets.

In the pancreas, what do the acini secrete?

The hormone-making islets make up only a small fraction of the organ; the acini do the digestive work.

What do the pancreatic delta cells produce?

Somatostatin is also the textbook example of a paracrine signal, acting on neighboring pancreatic cells.

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

Signs include obesity, a 'moon face' and hirsutism from the resulting excess cortisol.

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

It weakens the body's ability to hold blood pressure and blood sugar, which can be fatal.

Which disease involves an overactive thyroid producing excess T3 and T4?

Symptoms range from sweating and heat intolerance to bulging, swollen eyes.

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

Tertiary disease involves the hypothalamus and its releasing hormones.

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

Water-soluble hormones act at the cell surface; lipid-soluble steroids pass inside to the nucleus.

Signaling in which a cell's secretion acts on the same cell is called what?

Paracrine signals act on nearby cells; juxtacrine signaling requires direct membrane contact.

Which vertebrates are unique in having adrenal tissue organized into layers?

All vertebrates have adrenal tissue and a thyroid, which in amphibians drives the change from larva to adult.

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

Ernest Starling coined the term in 1905.

Who coined the word 'hormone' in 1905?

He and Bayliss had discovered secretin in 1902 while studying the pancreas.

Which hormone, found in 1902, is often wrongly called the first ever discovered?

Oliver and Schäfer's adrenal extract, containing adrenaline, beat it by several years.

Where are the S cells that make Bayliss and Starling's hormone located?

Secretin prompts the pancreas to release bicarbonate, neutralizing stomach acid entering the gut.

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

It is made in the pancreatic islets, the islands of Langerhans.

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

They worked in John Macleod's lab at the University of Toronto; Best won his place in a coin toss.

Who sequenced insulin's amino acids in 1951, making it the first fully sequenced protein?

Dorothy Hodgkin later determined its crystal structure in 1969.

How old was Banting when he won the Nobel Prize, its youngest medicine laureate ever?

He shared his half of the 1923 prize money with his student Charles Best.

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

The 14-year-old's first dose was so impure it caused an allergic reaction; a purer dose 12 days later worked.

Who discovered the pancreatic islets in 1869?

A healthy adult pancreas contains about a million of them, averaging 0.2 mm across.

The thyroid is usually described as having what shape?

Its two lobes sit below the Adam's apple, connected by a band called the isthmus.

What is the most common cause of hypothyroidism worldwide?

In iodine-sufficient regions, Hashimoto's thyroiditis takes over as the leading cause.

Which thyroid hormone is made by parafollicular rather than follicular cells?

It is made by parafollicular cells, distinct from the follicular cells making T3 and T4.

What is an enlargement of the thyroid gland called?

Over 90% of cases worldwide are due to iodine deficiency; the name comes from Latin gutturia, 'throat'.

How many parathyroid glands do humans usually have?

Each is a lentil-sized ovoid sitting behind the thyroid lobes.

Where are the adrenal glands located?

Their alternative name, suprarenal glands, says as much; the right one is pyramidal and the left crescent-shaped.

Which zone of the adrenal cortex produces cortisol?

The glomerulosa makes aldosterone, the reticularis makes androgens and the medulla makes catecholamines.

Which adrenal hormone helps regulate blood pressure and electrolyte balance?

It is a mineralocorticoid made in the outermost zona glomerulosa.

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

Cortisol raises blood sugar, suppresses the immune system and follows a daily rhythm.

Adrenaline plays an essential role in which bodily response?

It boosts blood flow to muscles, heart output, pupil dilation and blood sugar.

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

John Abel had already coined 'epinephrine' for his 1897 extract, which is why the US uses that name.

About how big is the human pituitary gland?

It weighs half a gram to a gram and sits in a bony pocket called the sella turcica.

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

Galen, centuries earlier, thought the 'little pine cone' merely propped up brain tissue.

The pineal gland's sleep hormone was first isolated from which animal?

Aaron Lerner's team found the extract lightened frog skin; it turned out to govern the sleep-wake cycle.

Growth hormone is secreted by somatotropic cells in which gland?

The 191-amino-acid peptide has been on the IOC's banned list since it was used in sport from at least 1982.

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

It regulates body temperature, hunger, thirst, sleep and circadian rhythms.

In which organ do T cells mature?

It is largest in childhood and gradually turns to fatty tissue from the early teens.