Corticosteroid Production and Regulation Flashcards
(27 cards)
What are steroid hormones derived from?
Enzymatic modification of cholesterol.
Where are enzymes that modify cholesterol found?
Mitochondria and smooth ER.
Where are steroid hormones stored?
Not stored - synthesised and immediately released.
Can steroid hormones travel freely in blood?
No as they are lipid soluble - must be complexed to specific binding globulins.
What arteries supply the adrenal glands?
Superior, middle and inferior suprarenal arteries.
What veins drain the adrenal glands?
Medullary vein –> suprarenal veins.
- drain into IVC on right
- left renal vein on left
Where are the nerves derived from that supply the adrenal gland, and what cell type do they innervate?
From coeliac plexus and thoracic splanchnic nerves.
Innervate chromaffin cells of adrenal medulla.
Describe the histology of the zona glomerulosa, the hormones it produces and what its regulated by.
Clusters of small cells containing fewer lipids than other areas.
Produces aldosterone (a mineralocorticoid). Regulated by aldosterone and K+.
Describe the histology of the zona fasciculata, the hormones it produces and what its regulated by.
Large cells arranged in cords.
Produces glucocorticoids - cortisol and corticosterone.
Regulated by ACTH.
Describe the histology of the zona reticularis, the hormones it produces and what its regulated by.
Smaller cells arranged in a haphazard arrangement.
Produces androgens - DHEA and DHEAs.
Regulated by ATCH and unknown factors.
What cells are found in the adrenal medulla and what is their function?
Chromaffin cells that produce catecholamines - adrenaline and noradrenaline.
What is the principle function of glucocorticoids?
Carbohydrate regulation (metabolism)
What is the principle function of mineralocorticoids?
Sodium/bp homeostasis
What is the principle function of DHEA/DHEAs?
Important source of androgens in women.
What is the rate-limiting enzyme in cholesterol biosynthesis?
HMG-coA reductase.
What is the first step of steroid biosynthesis and where does it occur?
Conversion of cholesterol to pregenolone.
Inner mitochondrial membrane.
What enzyme catalyses the fist step of steroid biosynthesis?
Cholesterol side-chain cleavage.
What is the rate-limiting step of the first step of steroid biosynthesis?
Transport of cholesterol from the cytoplasm into the inner mitochondrial matrix.
This is carried out by StAR - steroidogenic acute regulatory protein.
What is the most common enzyme deficiency in congenital adrenal hyperplasia?
21-hyroxylase - CYP21.
What is the C domain of the nuclear receptor superfamily?
DNA binding domain - 2 zinc fingers bind to specific sequences of DNA (hormone responsive elements).
What is the E domain of the nuclear receptor superfamily?
Ligand ending domain - binds steroid.
Where are glucocorticoid receptors found?
Widespread
Where are mineralocorticoid receptors found?
Distal nephron, salivary glands, sweat glands, large intestine, brain, heart and vascular tissue.
What catalyses the conversion of cortisol to inactive cortisone and why is this important?
11BHSDII
Cortisol is able to bind to mineralocorticoid receptors. It also is present in a much larger concentration than aldosterone in the blood, therefore is converted to its inactive form to allow aldosterone to function normally.
