Endocrine System Questions and Answers

Answer: D

The hormone not secreted by the placenta is Androgens (in the options given).

The placenta is an endocrine organ. Its syncytiotrophoblast secretes human chorionic gonadotropin (hCG), which keeps the corpus luteum alive in early pregnancy and is detected by pregnancy tests; human placental lactogen (hPL), which adjusts maternal metabolism to favour the foetus; and progesterone and oestrogens, which maintain the pregnancy.

The placenta lacks the enzyme system to make androgens itself and instead converts androgens supplied by the foetal and maternal adrenal glands into oestrogens. So androgens are the one option it does not produce as a hormone of its own.

Answer: A

The two gonadotropins are FSH and LH.

Gonadotropins are hormones of the anterior pituitary that act on the gonads. Follicle stimulating hormone (FSH) stimulates the growth of ovarian follicles and oestrogen secretion; luteinising hormone (LH) triggers ovulation and forms and maintains the corpus luteum.

Oestrogen and progesterone are ovarian steroid hormones produced in response to the gonadotropins, not gonadotropins themselves. So every option that includes either of them is wrong.

Answer: C

The hormone that is not a peptide is T4 (thyroxine).

Thyroxine is an iodinated derivative of the amino acid tyrosine, an amine hormone, not a chain of amino acids. It is fat-soluble enough to enter cells and acts on nuclear receptors.

GnRH (a decapeptide), FSH (a glycoprotein) and CCK (a gut peptide) are all made of amino-acid chains, so they are peptide or protein hormones.

Answer: B

Melatonin is secreted by the pineal gland.

The pineal gland, in the brain, secretes melatonin mainly in darkness. Melatonin signals day length to the body and so regulates daily rhythms and the breeding season of seasonal breeders such as sheep, goats and horses.

The adrenal gland secretes cortisol, aldosterone and adrenaline, the pituitary its trophic hormones, and the thyroid thyroxine; none secretes melatonin.

Answer: B

The hormone with no role in reproduction is glucagon.

Glucagon is made by the alpha cells of the pancreatic islets and raises blood glucose by stimulating glycogen breakdown and glucose production in the liver. It is a metabolic hormone.

The others all act in reproduction. Oxytocin contracts the uterus during labour and ejects milk during suckling. Prolactin stimulates milk production after delivery. Progesterone prepares the endometrium for implantation and maintains pregnancy.

Answer: A

The hormone that directly opposes insulin is glucagon.

Insulin, from the beta cells of the pancreas, lowers blood glucose by promoting uptake and storage. Glucagon, from the alpha cells of the same islets, does the opposite on the same targets: it raises blood glucose by breaking down liver glycogen and stimulating gluconeogenesis. The two are secreted in opposite directions as glucose rises and falls, which makes glucagon the direct antagonist.

Cortisol, epinephrine and growth hormone also raise blood glucose, but they are broader stress or growth hormones that act more slowly or through other pathways, so they are counter-regulatory rather than the direct opponent.

Answer: C

The feature that does not belong to type 1 diabetes is insulin resistance.

Type 1 diabetes is caused by autoimmune destruction of the beta cells of the pancreas, which leads to an absolute insulin deficiency. It most often begins in childhood or adolescence, and patients need insulin from the start.

Insulin resistance, where the tissues respond poorly to insulin that is present, is the hallmark of type 2 diabetes, usually in older and overweight adults. The other three options describe type 1 correctly, so they cannot be the answer.

Answer: B

The primary role of glucocorticoids is to promote the synthesis of glucose (gluconeogenesis).

Cortisol raises blood glucose. It increases the liver enzymes of gluconeogenesis and mobilises amino acids from muscle and glycerol from fat as raw material, so new glucose is made from non-carbohydrate sources. This is why excess steroids can cause hyperglycaemia.

Cortisol also lets the liver store some of this glucose as glycogen, but that follows from the extra glucose being made; it is not the primary role. Decreasing blood glucose and stimulating insulin secretion are the opposite of its effect, since glucocorticoids antagonise insulin.