Cortisol Flashcards
Where are the adrenal glands located
on the superior pole of the kidney in the retroperitoneal space
What are the two main parts of the adrenal gland
Adrenal cortex (75%) Adrenal Medulla (25%)
What type of gland is found in the adrenal medulla
A modified sympathetic ganglion (neuroendocrine gland).
What does the adrenal medulla secrete
Secretes catecholamines, mainly epinephrine (adrenaline) but also norepinephrine and dopamine (in smaller amounts)
What type of gland is found in the adrenal cortex
A true endocrine gland
What classes of hormone does the adrenal cortex secrete
Mineralocorticoids
Glucocorticoids
Sex Steroids
Name a Mineralocorticoids
Aldosterone
Name a glucocorticoid
Cortisol
What part of the cortex secrete glucocorticoids
Zona Fasciculata
What part of the cortex secrete minerlocorticoids
Zona glomerulosa
What part of the cortex secrete sex hormones
Zona Reticularis
Where is aldosterone synthase found
Zona glomerulosa
Where is 21 Hydroxylase found
Both glomerulosa and fasciculata
What does a defect in 21 Hydroxylase case
Defects in 21-hydroxylase is a common cause of congenital adrenal hyperplasia resulting in deficiency of aldosterone and cortisol and associated disruption of salt and glucose balance.
What are symptoms of a fetal Defect in 21-hydroxylase and why
Babies are born with malformed genitalia and if untreated it can be fatal.
Because, Androgen biosynthesis is unaffected so accumulating steroid precursors are channelled into excessive adrenal androgen production.
What are the levels of ACTH and CRH like in a 21 hydroxylase deficiency
HIGH (as lose inhibition)
What is cortisols function
Cortisol as a glucocorticoid is crucial in helping to protect the brain from hypoglycaemia. It has a permissive action on glucagon, which is vitals as glucagon alone is inadequate in responding to a hypoglycaemic challenge
How does cortisol travel in the blood
~95% of plasma cortisol is bound to a carrier protein, cortisol binding globulin (CBG)
When are cortisol levels highest
6am-9am
When are cortisol levels lowest
midnight
Does the ACTH or Cortisol last longer in the blood
Cortisol “burst” persists longer than ACTH burst because half-life is much longer.
What are the glucocorticoid actions of cortisol
Gluconeogenesis
Lipolysis
Proteolysis
Decreased Insulin Sensitivity
How does cortisol increase gluconeogenesis
- Cortisol stimulates formation of gluconeogenic enzymes in the liver thus enhancing gluconeogenesis and glucose production. This is aided by cortisol’s action on muscle (proteolysis)
How does cortisol increase Proteolysis
- cortisol stimulates the breakdown of muscle protein to provide gluconeogenic substrates for the liver.
How does cortisol increase lipolysis
- cortisol stimulates lipolysis in adipose tissue which increases [FFA] plasma creating an alternative fuel supply that allows [BG] to be protected (not used by muscles) while also creating a substrate (glycerol) for gluconeogenesis.
What are the non-glucocorticoid actions of cortisol
Negative effect on Ca2+ balance
Impairment of mood and cognition
Permissive effects on norepinephrine
Suppression of the Immune System
How does cortisol affect Calcium balance
Decrease absorption from gut, increases excretion at kidney resulting in net Ca2+ loss. Also increase bone resorption
What is the result of the
Permissive effects on norepinephrine of cortisol
vasoconstriction - particularly in vascular smooth muscle
How does cortisol suppress the immune system
Cortisol reduces the circulating lymphocyte count, reduces antibody formation and inhibits the inflammatory response. Latter effect can be useful clinically e.g. asthma/ulcerative colitis/organ transplant
