Peptide/steroid/amine hormones, HPA/HPT/HPG axes, insulin/glucagon, thyroid, adrenal, gonadal.
Endocrine System
Hormone
Signalling molecule secreted into circulation by endocrine gland, acting on distant target tissues. Classes: peptide/protein (insulin),…
Peptide hormone
Water-soluble polypeptide hormone binding cell-surface receptors (usually GPCR or RTK). Fast-onset, short half-life. Examples: insulin,…
Steroid hormone
Lipid-soluble cholesterol-derived hormone crossing plasma membrane to bind intracellular nuclear receptors. Slow-onset, long half-life.…
Hypothalamus-pituitary axis
Central regulator of endocrine output: hypothalamic releasing hormones → anterior pituitary trophic hormones → peripheral endocrine glands.…
Insulin
β-cell-secreted 51-aa peptide hormone binding insulin receptor (RTK). Promotes glucose uptake (GLUT4 translocation), glycogen synthesis,…
Glucagon
α-cell-secreted 29-aa peptide hormone binding hepatic glucagon receptor (GPCR → Gs → cAMP). Stimulates glycogenolysis + gluconeogenesis,…
Cortisol
Adrenal-cortex glucocorticoid; final output of HPA axis. Stress response: gluconeogenesis, lipolysis, anti-inflammatory, immunosuppressive.…
Thyroid hormone (T4/T3)
Iodinated tyrosine derivatives (T4: thyroxine, 4 iodines; T3: triiodothyronine, 3; T3 is active). Bind nuclear TR → basal metabolic rate,…
Endocrine negative feedback
Hormone output inhibits its own release via upstream hypothalamic + pituitary signals. Maintains homeostasis (cortisol-CRH-ACTH, thyroid…
Paracrine/autocrine/endocrine signalling
Distance hierarchy: autocrine (self), paracrine (neighbour), endocrine (via bloodstream). Juxtacrine (contact-dependent, Notch-Delta) and…