adrenal gland Flashcards
What are the two separate endocrine glands in the adrenal gland
Adrenal medulla
Adrenal cortex
What is the adrenal medulla
Neuroendocrine gland which secretes catecholamines - epinephrine (adrenaline), norepinephrine and dopamine
What is the adrenal cortex
True endocrine gland which secretes 3 classes of steroid hormones:
Mineralocorticoids e.g aldosterone - regulation of sodium and potassium
Glucocorticoids e.g cortisol - maintaining plasma glucose
Sex steroids e.g testosterone
What are the 3 zones of the adrenal cortex
Zona reticularis
Zona fasiculata
Zona glomerulosa
What does the zona glomerulosa secrete
mineralocorticoids - aldosterone
What does the zona fasciculata secrete
glucocorticoids - cortisol
What does the zona reticularis secrete
sex hormones
What does a defect in 21-hydroxylase cause
Congenital adrenal hyperplasia resulting in aldosterone and cortisol deficiency - this disrupts salt, potassium and glucose balance
The androgen synthesis is unaffected so there is an excessive production resulting in hyperplasia
What causes release of adrenocorticotropic hormone from the anterior pituitary gland
Corticotropin releasing hormone from the hypothalamus
What is the negative feedback for the hypothalamic-pituitary-adrenal pathway
Cortisol or ACTH
What is cortisol
Glucocorticoid hormone which influences glucose metabolism - 95% of it is bound to a carrier protein
which carrier protein does cortisol bind to
Cortisol binding globulin
Which cells have cytoplasmic glucocorticoid receptors
All cells with a nucleus
Why are glucocorticoids potent anti-inflammatories
They switch off the coding for enzymes which bring about the inflammatory response
What drives the peak in cortisol during the day
Peak in ACTH which occurs at 6-9am
What is the effect of cortisol on gluconeogenesis
Stimulates production of gluconeogenic enzymes in the liver which enhances production of glucose
What is the effect cortisol on proteolysis
Stimulates the breakdown of muscle protein to provide gluconeogenic substrates for the liver
What is the effect of cortisol
on lipolysis
Cortisol stimulates lipolysis which increases free fatty acid concentration in the plasma - allows for an alternative supply of fuel
What is the effect of cortisol on insulin sensitivity
Decreases insulin sensitivity of muscle and adipose tissue
What is the correlation between cortisol and insulin
Cortisol opposes the effects of insulin and is diabetogenic
What is the effect of cortisol on calcium
Decreases absorption from the gut and increases excretion of the calcium - also increases bone resorption which results in osteoporosis
What is the effect of cortisol on mood and cognition
It depresses mood and impairs cognitive function
Why is cushings disease (hypercortisolaemia) associated with hypertension
Because cortisol has a permissive effect on norepinephrine - particularly in smooth muscle which causes constriction
What is the effect of cortisol on the immune system
Suppression of the immune system - cortisol reduces lymphocyte count and inhibits the inflammatory reaction
What is the function of the mineralocorticoid, aldosterone
Acts on the kidney to determine the levels of minerals reabsorbed or excreted
It increases sodium reabsorption and potassium excretionat the distal tubule
What is the effect of increased aldosterone on blood pressure
Increased blood volume and therefore pressure
What is cushings syndrome
Hyper-secretion of cortisol due to tumour in the adrenal cortex
What is cushings disease
Hypercortisolism caused by a tumour in the pituitary gland
What are the characteristic features of cushings disease
Wastings of the exremeties due to the catabolic action of cortisol
Fat is distributed to the face and trunk
Striations are commonly seen on the abdomen in cushin
moon face
Buffalo hump
What is addisonian crisis
Life threatening hypotension and hypoglycaemia
What is addison’s disease
Autoimmune destruction of the adrenal cortex so no steroid hormones are produced
What does stress promote in relation to cortisol
Increases CRH and ACTH release so cortisol increases
What is the effect of alcohol and caffeine on the hypothalamo-pituitary-adrenal axis
depress the neurons involved in negative feedback and increasing levels of CRH and ACTH
What is the effect of high cortisol on the immune system
Leaves patient more prone to infection
What is pheochromocytoma
Rare neuroendocrine tumour qwhich is found in the adrenal medulla which causes excess catecholamins
