Lesson 11 of 11 · 13 min

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Must-know facts

20 facts

1Endocrine glands are ductless; hormones are non-nutrient intercellular messengers made in trace amounts.
2Hypothalamus: basal part of the diencephalon; GnRH stimulates gonadotrophin release, somatostatin inhibits GH release.
3Hypothalamic hormones reach the anterior pituitary through a portal circulation; the posterior pituitary is under direct neural control.
4Pars distalis: GH, PRL, TSH, ACTH, LH, FSH. Pars intermedia: MSH only. Pars nervosa: stores and releases oxytocin and vasopressin, made in the hypothalamus.
5GH excess in childhood: gigantism; GH deficiency: pituitary dwarfism; GH excess in adults: acromegaly.
6ADH (vasopressin) acts on the distal tubules; its impairment causes diabetes insipidus.
7LH: ovulation of Graafian follicles and maintenance of corpus luteum in females; androgen secretion in males.
8Melatonin from the pineal regulates the 24-hour (diurnal) rhythm.
9Thyroid: T₄ and T₃ need iodine; iodine deficiency gives goitre; hypothyroidism in pregnancy gives cretinism.
10Exophthalmic goitre (Graves' disease): hyperthyroidism with protruding eyeballs, raised BMR and weight loss.
11TCT lowers blood Ca²⁺; PTH raises it (hypercalcemic): bone resorption, renal reabsorption, intestinal absorption.
12Four parathyroids on the back of the thyroid; thymosins drive T-lymphocyte differentiation.
13Adrenal cortex from outside in: zona glomerulosa, zona fasciculata, zona reticularis.
14Cortisol: main glucocorticoid. Aldosterone: main mineralocorticoid (Na⁺ and water in, K⁺ and phosphate out).
15Adrenaline and noradrenaline (catecholamines) from the adrenal medulla are the fight-or-flight hormones.
16Addison's disease: underproduction of adrenal cortex hormones.
17About 1 to 2 million islets, only 1 to 2 per cent of pancreatic tissue; α-cells glucagon (hyperglycemic), β-cells insulin (hypoglycemic).
18Leydig cells make androgens; growing follicles make estrogen; corpus luteum makes mainly progesterone.
19ANF from the atrial wall lowers blood pressure; erythropoietin from juxtaglomerular cells stimulates RBC formation.
20Steroids and iodothyronines use intracellular receptors and act on genes; protein hormones use membrane receptors and second messengers (cAMP, IP₃, Ca⁺⁺).

Common traps

Where marks are lost

Saying the posterior pituitary makes oxytocin and vasopressin.

Both are made in the hypothalamus and carried down axons; the posterior pituitary only stores and releases them.

Mixing up diabetes insipidus and diabetes mellitus.

Insipidus: ADH problem, water loss and dehydration. Mellitus: prolonged hyperglycemia from insulin deficiency or resistance, glucose in urine and ketone bodies.

Calling glucagon hypoglycemic because it comes from the same islets as insulin.

Glucagon (α-cells) raises blood sugar; insulin (β-cells) lowers it. Think α for 'arise'.

Saying PTH lowers blood calcium.

PTH is hypercalcemic: it raises Ca²⁺ from bone, kidney and gut. TCT from the thyroid lowers it.

Listing the adrenal cortex zones as reticularis outermost.

From outside in: glomerulosa, fasciculata, reticularis (G-F-R).

Putting the parathyroids inside the thyroid or giving one pair only.

Four glands on the back side of the thyroid, one pair in each lobe.

Assuming every hormone enters its target cell.

Hormones with membrane-bound receptors (protein hormones) normally stay outside and act through second messengers; steroids and iodothyronines act on intracellular receptors.

Thinking only organised endocrine glands make hormones.

The heart (ANF), kidney (erythropoietin) and gut (gastrin, secretin, CCK, GIP) are not endocrine glands but secrete hormones.

Saying ACTH stimulates aldosterone secretion.

ACTH stimulates the adrenal cortex to make and secrete glucocorticoids (cortisol); aldosterone is a mineralocorticoid.

Key terms

22 terms

Endocrine gland: A ductless gland that releases its secretion, a hormone, without a duct.
Hormone: A non-nutrient chemical made in trace amounts that carries a message between cells.
Neurosecretory cells: Hypothalamic nerve cells, grouped as nuclei, that make and release hormones.
Portal circulation: The vessels that carry hypothalamic hormones to the anterior pituitary.
Adenohypophysis: Pars distalis plus pars intermedia; the glandular part of the pituitary.
Neurohypophysis: Pars nervosa or posterior pituitary; stores and releases oxytocin and vasopressin.
Gonadotrophins: LH and FSH, the pituitary hormones that stimulate the gonads.
Acromegaly: Disfigurement, mostly of the face, from excess GH in adults.
Diabetes insipidus: Water loss and dehydration when ADH synthesis or release is impaired.
Goitre: Enlargement of the thyroid, as in iodine deficiency.
Cretinism: Stunted growth and impaired development of a baby from hypothyroidism in pregnancy.
Hypercalcemic hormone: A hormone that raises blood Ca²⁺, such as PTH.
Thymosins: Thymus peptide hormones that drive T-lymphocyte differentiation and promote antibody production.
Catecholamines: Adrenaline and noradrenaline, the fight-or-flight hormones of the adrenal medulla.
Corticoids: Hormones of the adrenal cortex: glucocorticoids and mineralocorticoids.
Addison's disease: Weakness and fatigue from underproduction of adrenal cortex hormones.
Islets of Langerhans: The endocrine part of the pancreas, with glucagon-making α-cells and insulin-making β-cells.
Glycogenolysis: Breakdown of glycogen to glucose, stimulated by glucagon and catecholamines.
Leydig cells: Interstitial cells between the seminiferous tubules that make androgens.
Corpus luteum: The ruptured follicle after ovulation, which secretes mainly progesterone.
Atrial natriuretic factor: A peptide from the atrial wall that dilates vessels and lowers blood pressure.
Second messenger: A molecule such as cAMP, IP₃ or Ca⁺⁺ made inside the cell when a hormone binds a membrane receptor.

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