PY8.1-7 | Endocrine Physiology — Glossary

Short portal blood vessels connecting the hypothalamus to the anterior pituitary, allowing releasing/inhibiting hormones to reach pituitary cells without entering systemic circulation.

Regulatory mechanism where the end-product hormone inhibits further stimulation at the hypothalamus and/or pituitary; the fundamental control principle of endocrine axes.

Adenohypophysis; secretes FSH, LH, ACTH, TSH, prolactin, and GH under hypothalamic control via portal vessels.

Neurohypophysis; stores and releases ADH and oxytocin, which are synthesised in hypothalamic nuclei and transported down axons.

Hormone from supraoptic nucleus that acts on V2 receptors in the collecting duct to insert aquaporin-2 for water reabsorption; deficiency causes diabetes insipidus.

Syndrome of Inappropriate ADH secretion; excess ADH despite low plasma osmolality causing water retention and dilutional hyponatraemia.

Enzyme that oxidises iodide and catalyses organification and coupling reactions in thyroid hormone synthesis; target of autoantibodies in Hashimoto's thyroiditis.

Major thyroid hormone secretory product (90%); relatively inactive prohormone converted to active T3 by peripheral deiodinases.

Active thyroid hormone (5x more potent than T4); acts on nuclear receptors to increase BMR, thermogenesis, and growth.

Anterior pituitary hormone that stimulates thyroid follicular cells; the first-line screening test for thyroid function.

Autoimmune hyperthyroidism caused by TSH receptor antibodies (TRAb) that continuously stimulate thyroid hormone production.

Autoimmune thyroiditis with anti-TPO antibodies causing lymphocytic destruction of thyroid follicles; most common cause of hypothyroidism in iodine-sufficient areas.

Glucocorticoid from zona fasciculata regulated by CRH-ACTH axis; increases gluconeogenesis, has anti-inflammatory effects, and is the body's primary stress hormone.

Mineralocorticoid from zona glomerulosa regulated by RAAS and K+; promotes Na+ reabsorption and K+/H+ secretion in the collecting duct.

Clinical syndrome of cortisol excess characterised by moon face, central obesity, purple striae, hyperglycaemia, and proximal myopathy.

Primary adrenal insufficiency with cortisol and aldosterone deficiency; presents with hyperpigmentation, hypotension, hyperkalaemia, and hyponatraemia.

Anabolic peptide hormone from pancreatic beta cells that promotes glucose uptake (via GLUT4), glycogen synthesis, lipogenesis, and protein synthesis.

Catabolic peptide hormone from pancreatic alpha cells that raises blood glucose via glycogenolysis, gluconeogenesis, lipolysis, and ketogenesis.

Insulin-responsive glucose transporter in skeletal muscle and adipose tissue; translocated to the cell membrane when insulin binds its receptor.

Glycated haemoglobin reflecting average blood glucose over 2-3 months (RBC lifespan); diagnostic threshold for diabetes is ≥ 6.5%.

Life-threatening complication of insulin deficiency (mainly T1DM): uninhibited lipolysis → ketogenesis → metabolic acidosis with high anion gap.

Hormone from parathyroid chief cells that raises serum Ca2+ by increasing bone resorption, renal Ca2+ reabsorption, and vitamin D activation.

Active form of vitamin D produced in the kidney by 1-alpha-hydroxylase (stimulated by PTH); increases intestinal absorption of Ca2+ and PO4.

Insulin-like growth factor produced by the liver in response to GH; mediates the anabolic growth effects of GH including linear bone growth.

Growth hormone excess after epiphyseal closure causing enlargement of hands, feet, jaw, and soft tissues; most commonly caused by a pituitary adenoma.