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50 free Endocrine System trivia questions with answers — science & nature quiz, new questions added Aug 2026.
The endocrine system is the body's slow mail: glands with no ducts dropping hormones straight into the blood to tell distant organs what to do. An almond-sized hypothalamus runs it through a kidney-bean-sized pituitary, and a pine-cone-shaped gland decides when you get sleepy. These 50 questions cover the anatomy and physiology students meet in biology and A&P classes: the major glands and what each secretes, the anterior and posterior pituitary, alpha, beta and delta cells, parathyroid hormone and calcium, the zones of the adrenal cortex, autocrine versus paracrine signaling, and the classic disorders: Cushing's, Addison's, Graves' and goitre. There is history too, from Starling coining 'hormone' to Banting and Best isolating insulin and Leonard Thompson's first injection. Every answer is cited to a page we checked. Play it solo, or print it for a classroom or study-group round.
30 of 50 questions with answers and explanations. Play the quiz
Q 01Endocrine glands release their hormones directly into what?
The bloodstream
That is the difference from exocrine glands like salivary glands, which use ducts.
Q 02Which brain region is the neural control center for the endocrine system in vertebrates?
Hypothalamus
It links the nervous system to the endocrine system through the pituitary gland just below it.
Q 03What is the study of the endocrine system and its disorders called?
Endocrinology
It is a branch of internal medicine.
Q 04Which of these hormones is secreted by the thyroid?
Thyroxine
Thyroxine is T4; the gland also makes T3 and calcitonin.
Q 05Which hormone does the pineal gland secrete?
Melatonin
The pine-cone-shaped gland sits near the center of the brain and helps set the sleep-wake cycle.
Q 06Glands that signal each other in sequence are often called what?
An axis
The hypothalamic-pituitary-adrenal axis is the classic example.
Q 07Which hormone does the kidney secrete to stimulate red blood cell production?
Erythropoietin
Synthetic versions, known as EPO, became notorious as a doping agent in endurance sport.
Q 08Which of these is an exocrine gland rather than an endocrine one?
Salivary
Exocrine glands have ducts or a hollow lumen; endocrine glands have no ducts.
Q 09The pituitary gland is divided into which two main parts?
Anterior and posterior
The posterior lobe stores hormones made in the hypothalamus; the anterior lobe makes its own.
Q 10Which posterior pituitary hormone helps the body retain water?
ADH
Also called ADH or vasopressin, it is synthesized in the hypothalamus's supraoptic nucleus.
Q 11Which hormone induces uterine contractions and stimulates lactation?
Oxytocin
It is sometimes nicknamed the 'cuddle hormone' for its role in bonding.
Q 12The parathyroid glands release their hormone in response to low levels of what?
Calcium
Parathyroid hormone acts on bone, kidneys and gut to raise blood calcium, and activates vitamin D.
Q 13Which pancreatic cells produce glucagon?
Alpha
Glucagon tells the liver to release stored sugar when blood glucose runs low.
Q 14Roughly what share of pancreatic islet cells are insulin-making beta cells?
Q 21What does a hormone bind to in a target cell to change its function?
A receptor protein
Water-soluble hormones act at the cell surface; lipid-soluble steroids pass inside to the nucleus.
Q 22Signaling in which a cell's secretion acts on the same cell is called what?
Autocrine
Paracrine signals act on nearby cells; juxtacrine signaling requires direct membrane contact.
Q 23Which vertebrates are unique in having adrenal tissue organized into layers?
Mammals
All vertebrates have adrenal tissue and a thyroid, which in amphibians drives the change from larva to adult.
60%
Delta cells, which make somatostatin, are only about 5% of the islets.
Q 15In the pancreas, what do the acini secrete?
Digestive enzymes
The hormone-making islets make up only a small fraction of the organ; the acini do the digestive work.
Q 16What do the pancreatic delta cells produce?
Somatostatin
Somatostatin is also the textbook example of a paracrine signal, acting on neighboring pancreatic cells.
Q 17Which disease is caused by hypersecretion of ACTH from a pituitary adenoma?
Cushing's
Signs include obesity, a 'moon face' and hirsutism from the resulting excess cortisol.
Q 18Which disease results from too little cortisol due to adrenal insufficiency?
Addison's
It weakens the body's ability to hold blood pressure and blood sugar, which can be fatal.
Q 19Which disease involves an overactive thyroid producing excess T3 and T4?
Graves'
Symptoms range from sweating and heat intolerance to bulging, swollen eyes.
Q 20Which type of endocrine disease points to a problem with the pituitary gland?
Secondary
Tertiary disease involves the hypothalamus and its releasing hormones.
Q 24The word 'hormone' comes from a Greek word meaning what?
Setting in motion
Ernest Starling coined the term in 1905.
Q 25Who coined the word 'hormone' in 1905?
Ernest Starling
He and Bayliss had discovered secretin in 1902 while studying the pancreas.
Q 26Which hormone, found in 1902, is often wrongly called the first ever discovered?
Secretin
Oliver and Schäfer's adrenal extract, containing adrenaline, beat it by several years.
Q 27Where are the S cells that make Bayliss and Starling's hormone located?
The duodenum
Secretin prompts the pancreas to release bicarbonate, neutralizing stomach acid entering the gut.
Q 28Insulin's name comes from the Latin word for what?
Island
It is made in the pancreatic islets, the islands of Langerhans.
Q 29Which two researchers first isolated insulin from dog pancreas in 1921?
Banting and Best
They worked in John Macleod's lab at the University of Toronto; Best won his place in a coin toss.
Q 30Who sequenced insulin's amino acids in 1951, making it the first fully sequenced protein?
Frederick Sanger
Dorothy Hodgkin later determined its crystal structure in 1969.