HP-07 in 10 Sentences

The endocrine system consists of ductless glands that secrete hormones into the bloodstream to coordinate body functions, working slower but longer-lasting than the nervous system.
The hypothalamus is the master coordinator, producing releasing hormones (GnRH, CRH, TRH, GHRH) and inhibiting hormones (somatostatin, PIF/dopamine) to control the anterior pituitary.
The anterior pituitary produces six tropic hormones (FLAT PG: FSH, LH, ACTH, TSH, Prolactin, GH), while the posterior pituitary only stores and releases ADH and oxytocin, which are synthesised in the hypothalamus.
The thyroid gland produces T3 and T4 (iodine-dependent regulators of BMR and growth) and calcitonin from C-cells, which lowers blood calcium; the parathyroid glands produce PTH, which raises blood calcium.
The adrenal cortex has three zones (GFR = Salt-Sugar-Sex): glomerulosa makes aldosterone (Na+ balance), fasciculata makes cortisol $\frac{stress}{gluconeogenesis}$ , and reticularis makes androgens; the adrenal medulla makes adrenaline and noradrenaline for fight-or-flight.
The pancreatic islets of Langerhans contain α-cells (glucagon — raises glucose), β-cells (insulin — lowers glucose, the only hypoglycaemic hormone), and δ-cells (somatostatin — inhibits both).
Peptide hormones act via surface receptors and cAMP second messengers; steroid and thyroid hormones are lipid-soluble, cross cell membranes, and act via intracellular receptors to directly regulate gene expression.
All major axes are regulated by negative feedback: the end-hormone inhibits its upstream hypothalamic and pituitary drivers, maintaining hormonal homeostasis.
Key disorders include gigantism/acromegaly $\frac{GH excess before}{after plate fusion}$ , cretinism/myxoedema $\frac{childhood}{adult hypothyroidism}$ , Addison's/Cushing's $\frac{adrenal cortex hypo}{hyper}$ , Graves' disease (autoimmune hyperthyroidism with exophthalmos), and Type 1/Type 2 diabetes mellitus.
The single most important NEET fact in this chapter is that ADH and oxytocin are synthesised in the hypothalamus and merely stored and released from the posterior pituitary.