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…
HPA pulsatility delay-feedback model
Hypothalamic-pituitary-adrenal axis exhibits ultradian (~hourly) cortisol pulses arising from delay-differential equation dC/dt = α A(t-τ)…
Allostasis homeostatic set-point control
Sterling-Eyer (1988) allostasis: adaptive setpoint regulation maintains stability via change. Set-point x* is fixed point of dx/dt = -k(x -…
HPA axis (cortisol negative feedback)
Selye 1936 + Yates-Maran 1974: hypothalamus-CRH -> pituitary-ACTH -> adrenal-cortisol; cortisol negative-feedback to hypothalamus +…
Insulin-glucose minimal model (Bergman)
Bergman-Cobelli 1979 minimal-model: dG/dt = -p1 G - X G + meal; dX/dt = -p2 X + p3 (I - I_b); insulin-sensitivity Si = p3/p2; clinical…
HPT axis (thyroid feedback)
Pitt-Rivers / Tata 1950s thyroid-hormone-axis: TRH -> TSH -> T4/T3; T3-bound nuclear receptor (TR alpha + TR beta) regulates…
Menstrual cycle (Knobil GnRH pulse)
Knobil 1980s GnRH pulse-generator + LH/FSH dynamics; menstrual + estrous cycles emerge from estradiol negative-then-positive feedback at…
Growth hormone / IGF-1 axis
Daughaday-Salmon 1957 somatomedin + Le Roith 1990s IGF-1 receptor: hypothalamus-GHRH -> pituitary-GH -> liver-IGF-1; mediates postnatal…
Calcium homeostasis (PTH + vit D)
DeLuca 1973 1,25-(OH)2 vit D3 + Brown 1993 calcium-sensing-receptor CaSR: Ca2+ low -> PTH up -> renal 1-alpha-hydroxylase -> calcitriol ->…
Hormone concept (Starling 1905)
E Starling 1905 'hormone' coinage; modern endocrine + paracrine + autocrine + intracrine + neuroendocrine extensions.
Insulin (Banting-Best 1922)
F Banting-C Best 1922 (Nobel 1923) insulin-isolation; modern recombinant + glargine + smart-insulin glucose-responsive 2024.
GLP-1 (Bell 1983)
G Bell 1983 GLP-1 cloning; modern semaglutide / tirzepatide / retatrutide; obesity + cardiovascular Nobel-pending applications.
HPA axis (Selye 1936)
H Selye 1936 GAS general-adaptation-syndrome; modern HPA-axis cortisol + CRH + ACTH stress-response and depression-link.
Steroid receptor (Jensen 1958)
E Jensen 1958 estrogen-receptor; modern tamoxifen + aromatase-inhibitors + degraders ARV-471 ligand-induced-degradation.
Pendrin (Everett 1997)
L Everett 1997 SLC26A4 / pendrin; modern Pendred-syndrome + iodide-transport + thyroid-cancer Tg-I131 ablation.