Adrenal hormones Flashcards
Parts of the adrenal gland and what they make
Cortex: Zona glomerulosa (aldosterone (mineralcorticoid)), zona fasciculata (glucocorticoids: cortisol), zona reticularis (androgens); and medulla: epi and norepi
Name some steroid hormones and talk about their effects
Aldosterone, cortisol, progesterone, testosterone, estrogen, (vitamin D). All derived from cholesterol. Very complex, varied response due to DNA binding site variance. Dysfunction is often related to enzyme defects in synthesis
Synthesis of steroid hormones map
Chart. Important enzymes are 21-hydroxylase (needed for cortisol and aldosterone) and aromatase (needed to convert testosterone to estrogen)
What is the main defect in Congenital adrenal hyperplasia
21-hydroxylase - so cortisol and aldosterone low
What causes release of CRH, which then releases ACTH?
Physical/emotional stress, hypoglycemia, cold, pain.
What are symptoms of adrenal insufficiency?
Low aldosterone, high K, crave salt. 1˚: adrenal dysfunction. 2˚ and 3˚: hypothalamus or pituitary dysfunction.
Regulation of crystal secretion
CRH - ACTH - cortisol. Pulsatile release - key for function; Otherwise the receptors would down regulate. Highest from 6-10am and lowest at midnight. Goes up within 40 minutes of ACTH release.
4th part of pituitary that releases hormone!
pars tuberalis. releases glycosylated TSH. Affected by sunlight, induces seasonal behaviour (ie hibernating, migration). Affects our cortisol etc.
Cortisol transport
Most bound to cortisol binding globin. Some to albumin, very little free.
Functions of cortisol (list)
Glucose metabolism. Catabolic effects. Affects Minerals, Immune system, Cardiovascular system, CNS
Function of cortisol on glucose metabolism
gluconeogenesis and glycogen storage in liver; decreases muscle glucose utilization; increases blood glucose, thus making glucose available for insulin insensitive tissues (tissues that don’t require insulin for glucose uptake: brain, heart, kidney, red blood cells).
Catabolic Function of cortisol
stimulates breakdown of proteins to amino acids, stimulates lipolysis
Function of cortisol on minerals
electrolyte/H2O balance (high cortisol has an effect on mineralocorticoid receptors: salt and water retention); antagonizes actions of Vitamin D and impairs calcium absorption
Function of cortisol on immune system
immunosuppression (lower lymphocyte infiltration, lower lymphocyte numbers, suppress cell-mediated hypersensitivity, impairs phagocytes). decreases inflammation. Used in transplants, arthritis, etc.
Function of cortisol on cardiovascular system
(not major). maintains integrity of CV system (lower permeability of capillary endothelium, inotropic action on myocardium, facilitates vasoconstriction). Used in ICU so you don’t get edema, ie in lungs.
Function of cortisol on CNS
(euphoria, reduces seizure threshold, can produce psychotic responses in high doses)
How does pigmentation relate to cortisol?
ACTH is made from same pro hormone as MSH, so if adrenal is not producing enough cortisol, ACTH goes up and with it MSH.
What lowers cortisol?
Omega 3 fatty acids, Music (depends on music!), Massage therapy, Laughing, and the experience of humour, Crying, Vitamin C blunts cortisol release in response to mental and physical stressors, regular dancing to Argentinian tango, sexual intercourse, black tea may hasten recovery from high cortisol states
What increases cortisol levels?
Caffeine, Sleep deprivation, Intense or prolonged physical exercise, Hypoestrogenism, Melatonin supplementation, Burnout, Anorexia nervosa, Severe trauma or stressful events, Stimulation of the serotonin receptor gene 5-HT2C, Oral contraceptive pills can in young women who perform whole-body-resistance exercise training (may cause a reduction in the ability to gain muscle mass by weight training), Subcutaneous adipose tissue regenerates cortisol from cortisone, Commuting increases cortisol levels relative to length of trip
General Function of aldosterone
Increase Na reabsorption, which leads to increase water retention, and K excretion
How does aldosterone increase Na reabsorption?
it stimulates transcription Na/K ATPase, leading to more sodium pumps in nephron. also stimulates expression of a Na channel which facilitates uptake of sodium from tubular lumen. Has effects on sweat glands, salivary glands and the colon (bascially same as distal tubule of kidney)
Membrane binding sites for aldosterone?
Exist in heart and blood vessels to help increase BP
Pathway leading to aldosterone release
Lower blood flow to kidneys (ie lower volume), kidney releases renin, which cleaves angiotensiogen to angiotensin I, ACE cleaves this to angiotensin II, which then acts on adrenal to release aldosterone.
Control of aldosterone secretion?
Release. Major: increased K (direct effect on adrenal), Angiotensin II (via renin etc). Minor: ACTH, low Na. Inhibit aldosterone: high Na, low K, atrial natriuretic peptide
