Adrenal hormones Flashcards
Adrenal hormones
Corticosteroids (Glucocorticoids, mineralocorticoids) and androgens
Produced by the adrenal cortex
Corticosteroids are catabolic (breakdown muscle)
Androgens are anabolic (build muscle)
All Synthesised from cholesterol
Aldosterone
A mineralocorticoid
Synthesised in the zona glomerulosa
Increases sodium retention and potassium elimination
Cortisol
A glucocorticoid
Synthesised in the zona fascilata
Secretion occursin a circadium rhythm but also in response to stress.
Androgens
Synthesised in the zona reticularis
Synthetic corticosteroids
Given in the morning to prevent inhibition
Can be used to treat asthma or severe allergy as inhibit histamine synthesis.
Stops response to stress, increased risk of shock.
Actions of glucocorticoids
Metabolic actions - increase blood glucose, stimulates gluconeogenesis in the liver, inhibits glucose uptake hy many tissues (not brain) stimulates protein breakdown in muscle and lipolysis in adipose tissue.
Anti-inflammatory and immunosuppressive actions - decreases immune response, lymphocyte number and antibody production. Used as therapy to prevent transplant rejection - long term use increases cancer risk.
Mechanism of action of glucocorticoids
Steroid/ receptor complex binds to AP-1 stopping it from activating DNA leading to decreased protein synthesis. Secretion is controlled by negative feedback to the hypothalamus. Hypothalamic corticotrophin releasing hormone (CRH) acts on the anterior pituitary to release ACTH which acts on the adrenal cortex stimulating release of glucocorticoids, this feeds back to the hypothalamus, inhibiting CRH release.
Actions of mineralocorticoids
Acts on distal convoluted tubules and collecting ducts of kidney to regulate sodium and potassium retention.
Aldosterone increases sodium retention and potasium elimination. Acts on aldosterone receptor to produce permease making cells more permeable to sodium, increasing sodium influx.
Role in water balance and BP
Control of mineralocorticoid secretion
Angiotensin II acts on the adrenal cortex by stimulating aldosterone release, this afts on the kidney and affects osmolarity which feeds back to the osmoreceptors in the hupothalamus and helps maintain water balance by decreasing or increasing ADH. Angiotensinogen is constituitively released from liber into blood circulation feeding the synthesis of angiotensin II, little is known about the control of angiotensinogen
Problems with corticosteroid secretion
Cushing's syndrome Cushing's disease Conn's syndrome Addison's disease Congenital Adrenal hyperplasia Oat-cell carcinoma of lung
Cushing’s syndrome
Often caused by adrenal tumours
Excess glucocorticoid produced
Moon face, weight gain, abdominal striae, muscle wastage
Treated by inhibiting glucocorticoid release (metyrapone,ketoconazole and aminogluthethimide)
Cushing’s disease
Pituitary tumour producing ACTH
Drives cortisol release from arrenal cortex
Remove tumour to treat
Conn’s syndrome
Excess mineralocorticoid
Potasium depletion and sodium retention
Hypertension and muscle weakness
Treat with aldosterone antagonist (spironolactone)
Addison’s disease
Non-functional adrenals
Can be caused by TB
Leads to hyposecretion of corticosteroids
Hyperpigmentation, poor response to stress, hypoglycemia and electrolyte imbalance
Life threatening
Treat with HRT - synthetic mineralo- and glucocorticoids
(fludrocortisone and dexamethasone)
Congenital adrenal hyperplasia
Do not have enzyme to produce corticosteroids (21b-hydroxylase), increases androgens and decreases or inhibits corticosteroids (depends how much enzyme activity is lacking) leads to birth defects and masculinisation in females
