Glossary — Key Terms, Definitions, and NEET Significance — Notes

Term	Definition	NEET Significance
Endocrine gland	Ductless gland; secretes hormones into blood	Distinguishes from exocrine glands
Hormone	Chemical messenger secreted by endocrine gland; travels via blood to act on target organ	Foundation concept
Hypothalamus	Master coordinator; produces releasing/inhibiting hormones controlling anterior pituitary	Most hormones of the body trace to here
Adenohypophysis	Anterior pituitary; glandular tissue; produces FLAT PG	Distinguish from neurohypophysis
Neurohypophysis	Posterior pituitary; neural tissue; stores ADH and oxytocin (made in hypothalamus)	Synthesis site = NEET trap
Negative feedback	End product inhibits its own upstream production; maintains homeostasis	Universal endocrine regulatory mechanism
Tropic hormone	Hormone that acts on another endocrine gland to stimulate hormone release	TSH, ACTH, FSH, LH all tropic
Calcitonin	Peptide from thyroid C-cells; lowers blood Ca2+	Antagonist of PTH
PTH (Parathormone)	Peptide from parathyroid; raises blood Ca2+ via bone resorption, renal reabsorption, vitamin D activation	Antagonist of calcitonin
Mineralocorticoid	Steroid hormone regulating mineral (Na+/K+) balance; primary = aldosterone	Zona glomerulosa product
Glucocorticoid	Steroid hormone regulating glucose metabolism and stress; primary = cortisol	Zona fasciculata product
cAMP	Cyclic AMP; second messenger for peptide hormones; produced from ATP by adenylyl cyclase	Mechanism for peptide hormones
IGF-1	Insulin-like Growth Factor-1; made by liver in response to GH; mediates bone growth	GH's downstream effector
Gigantism	Excess GH in childhood; proportionate excessive height before growth plate fusion	Distinguish from acromegaly
Acromegaly	Excess GH in adults; enlarged extremities/facial features; no height increase	After growth plate fusion
Cretinism	Childhood hypothyroidism; stunted growth + irreversible mental retardation	Iodine or T4 deficiency congenital
Myxoedema	Adult hypothyroidism; puffy face, low BMR, lethargy	Reversible unlike cretinism
Addison's disease	Adrenal cortex hyposecretion; hypoglycaemia, weakness, dark skin	ACTH excess → MSH effect
Cushing's syndrome	Adrenal cortex hypersecretion of cortisol; moon face, buffalo hump, hyperglycaemia	May be pituitary or adrenal cause
Graves' disease	Autoimmune hyperthyroidism; TSI mimics TSH; exophthalmos	TSI = thyroid-stimulating immunoglobulin
Tetany	Sustained muscle spasm from hypocalcaemia; caused by PTH deficiency	Carpopedal spasm, Chvostek's sign
Diabetes mellitus	Insulin deficiency (Type 1) or resistance (Type 2); hyperglycaemia	Most common endocrine disorder
Diabetes insipidus	ADH deficiency/insensitivity; massive dilute urine; normal blood glucose	Contrast with DM
Goitre	Thyroid enlargement; simple = iodine deficiency; toxic = Graves'	TSH drives thyroid hyperplasia
Catecholamine	Amine hormone derived from tyrosine; adrenaline and noradrenaline	Adrenal medulla products
Somatomedin (IGF-1)	GH-induced liver protein mediating bone growth	Downstream mediator of GH
Chromaffin cells	Adrenal medullary cells; modified sympathetic neurons; neural crest origin	Secrete catecholamines
Islets of Langerhans	Endocrine clusters in pancreas; α, β, δ cells	Insulin, glucagon, somatostatin
Thymosin	Peptide from thymus; drives T-cell maturation and differentiation	Cell-mediated immunity
Melatonin	Indole amine from pineal gland; regulates circadian rhythm	Darkness hormone