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Steroid hormones
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aldosterone, cortisol, testosterone, oestrogen
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Tyroid hormones
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T3 & T4
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Gases
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nitric oxide (hormone & neurotransmiter)
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Hormone + source
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control
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Action
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PTH from chief cells
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low blood Ca2+ levels stimulate secretion (& vice versa)
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increases blood Ca2+ & Mg2+ levels & decreases blood HPO42- level, increases bone resorption by osteoclasts, increases Ca2+ reabsorption * HPO42- excretion by kidneys, promotes formation of calcitriol (vit D active form) which increases rate of dietary Ca2+ & Mg2+ absorption.
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Hormone + source
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control
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Action
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a) cortex hormones
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1. mineralocorticoids from zona glomerulosa cells
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increased blood K+ level & angiotensin II stimulate secretion
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increase blood levels of Na+ & water, decrease blood level of K+
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2. glucocorticoids from zona fasiculata cells
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ACTH stimulates release; corticotropin-releasing hormone promotes ACTH secretion in response to stress & low blood levels of glucocorticoids
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increase protein breakdown (except in liver), stimulate gluconeogenesis & lipolysis, provide resistance to stress, dampen inflammation, depress immune responses
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3. androgens from zona reticularis cells
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ACTH stimulates secretion
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assist in early growth of axillary & pubic hair in both sexes, in females - contribute to libido & are source of oestrogen after menopause
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b) medulla hormones
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1. adrenaline/noradrenaline from chromaffin cells
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sympathetic preganglionic neurons release ACh which stimulates secretion
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enhances effects of sympathetic division of autonomic nervous system during stress
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Amine hormones
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adrenaline, noradrenaline, dopamine
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(tyrosine)
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histamine
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(histidine)
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serotonin & melatonin
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(tryptophan)
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Peptide/Protein hormones
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amino acid polymers 3-49aa/50-200aa
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(peptide) oxytocin, ADH
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(protein) human growth, insulin
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eicosanoid hormones
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derived from arachidonic acid/membrane lipids. Prostaglandins & leukotrienes. Local hormones secreted by all cells (except RBCs).
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Hormone
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Target tissues
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Action
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hGH
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liver
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stimulates liver, muscle, cartilage & bone to synthesise & secrete insulin-like growth factos (IGFs) which promote growth of body cells, protein synthesis, tissue repair, lipolysis & elevates blood [glucose].
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TSH
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thyroid gland
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stimulates synthesis & secretion of thyroid hormones
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FSH
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ovaries & testes
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initiates development of oocytes & induces ovarian secretion of estrogens/ stimulates testes to produce sperm
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LH
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ovaries & testes
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stimulates secretion of oestrogen & progesterone, ovulation & formation of corpus luteum/ stimulates testes to produce testosterone
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prolactin (PRL)
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mammary glands
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promotes milk production
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ACTH
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adrenal cortex
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stimulates secretion of glucocorticoids
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MSH
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brain
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exact role unknown, may influence brain activity, excess can cause skin darkening
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Hormone + source
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control
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Action
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glucagon from alpha cells of pancreatic islets
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decreased blood level of glucose, exercise, & mainly protein meals stimulate secretion, somatostatin (growth hormone) & insulin inhibits.
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raises blood glucose by accelerating glycogen breakdown into glucose in liver (glycogenolysis), converting other nutrients into glucose in liver (gluconeogenesis) & releasing glucose in blood
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insulin from beta cells of pancreatic islets
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increased blood level of glucose, ACh, arginine & leucine, glucagon GIP, hGH, & ACTH stimulate, somatostatin inhibits
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lowers blood glucose by accelerating transport of glucose into cells, converting glucose into glycogen & decreasing glycogenolysis & gluconeogenesis, increases lipogenesis & stimulates protein synthesis
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somatostatin from delta cells of pancreatic islets
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pancreatic polypeptide inhibits
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inhibits secretion of insulin & glucagon, slows absorption of nutrients from GI tract
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pancreatic polypeptide from F cells of pancreatic islets
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meals with protein, fasting, exercise & acute hypoglycemia stimulate, somatostatin & elevated blood glucose inhibit
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inhibits somatostatin secretion, gallbladder contraction & secretion of pancreatic digestive enzymes
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permissive effect
requires recent/simultaneous exposure to 2nd hormone
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synergistic effect
two hormones have greater impact than individually
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antagonistic effect
two hormones have opposing actions
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Hormone + source
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control
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Action
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T3 & T4 from follicular cells
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secretion increased by TRH which stimulates release of TSH in response to low thyroid hormone levels, low metabolic rate, cold, pregnancy & high altitudes. TRH/TSH secretions inhibited by high thyroid hormone levels & high iodine level
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increase basal metabolic rate, stimulate protein synthesis, increase glucose & fatty acid use for ATP production, increase lipolysis, enhance cholesterol excretion, accelerate body growth, contribute to nervous system development
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calcitonin (CT) from parafollicular cells
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high blood Ca2+ levels stimulate secretion (& vice versa)
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lowers blood levels of Ca2+ & HPO42- by inhibiting bone resorption by osteoclasts & by accelerating calcium/phosphate uptake into bone extracellular matrix
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testosterone
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stimulates descent of testes before birth, regulates spermatogenesis, promotes development & maintenance of male secondary sex characteristics
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inhibin
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inhibits secretion of FSH from anterior pituitary
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Hormone
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Target tissues
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control
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action
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oxytocin
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uterus, mammary glands
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neurosecretory cells of hypothalamus secrete OT in response to uterine distention & stimulation of nipples
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stimulates contraction of smooth muscle cells of uterus during childbirth; stimulates contraction of myoepithelial cells in mammary glands to cause milk ejection
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ADH
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kidneys, arterioles, sudoriferous (sweat) glands
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neurosecretory cells of hypothalamus secrete ADH in response to elevated blood osmotic pressure, dehydration, loss of blood volume, pain or stress; inhibitors of ADH are low blood osmotic pressure, high blood volume & alcohol
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conserves water by decreasing urine volume, decreases water loss through perspiration, raises BP by constricting arterioles
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Hormone
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action
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estrogens & progesterone
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together with gonadotropic hormones of anterior pituitary, regulate female reproductive cycle & oogenesis, maintain pregnancy, prepare mammary glands for lactation & promote development & maintenance of female secondary sex characteristics
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relaxin
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increases flexibility of pubic symphysis during pregnancy, helps dilate uterine cervix during labour & delivery.
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inhibin
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inhibits secretion of FSH from anterior pituitary
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skin
vit D - mineral homeostasis
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liver
angiotensinogen - increases BP
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small intestine
secretin - increases pancreatic juice secretion
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heart
ANP - decreases bp
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stomach
gastrin - increases stomach motility
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kidney
EPO - increases RBC production
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