Adrenal gland Flashcards
1
Q
Adrenal cortex origin and secretion
A
- Derived from mesoderm
- Glucocorticoids (zona fasciculata), mineralcorticoids (zona glomerulosa), androgens (zona fasciculata/reticularis)
2
Q
Adrenal medulla origin and secretion
A
- Derived from neural crest
- Epinephrine, norepi, dopa, and dopamine
- Modified post-ganglionic sympathetic nerve cells
3
Q
Steroid hormone synthesis in adrenal cortex
A
- Precursor is cholesterol, LDL cholesterol, or de novo
- All enzymes are p450 oxidases except cytosolic 3B-hydroxysteroid dehydrogenase
- Rate limiting step is cholesterol to pregnenolone
4
Q
Aldosterone synthesis in zona glomerulosa
A
- Glomerulosa lacks 17alpha-hydroxylase but has aldosterone synthase
- No storage pool of aldosterone
- Reabsorption of Na and water in kidney, K secretion
5
Q
Cortisol and androgen synthesis in zona fasciculata/reticularis
A
- Have 17-alpha hydroxylase
- Most cortisol is bound to CBP or albumin, some free
- DHEA and Androstenedione are adrenal androgens, converted in peripheral tissues
6
Q
Cortisol mechanism of action
A
- Free cortisol enters target cell by diffusion
- Binds to cytoplasmic receptor
- Migrates to the nucleus
- Modulates gene transcription
- Inhibits expression of CRH receptor and ACTH and transcription of POMC gene
7
Q
11B-hydroxysteroid dehydrogenase type 2
A
- Converts cortisol to cortisone in the kidney
- Prevents sensing of cortisol as a mineralcorticoid
- Present in renal tubule cells
8
Q
Cortisol action
A
- Stimulates gluconeogenesis in liver, enhances protein breakdown, stimulates lipolysis, deposits fat centrally, decreases osteoblastic activity
- Inhibits cytokine and chemoattract molecule production, stabilizes lysosomal enzymes, contributes to vasoconstriction
- Decreases lymphocyte proliferation, inhibits hypersensitivity reactions
- Emotional instability
- Blocks glucose uptake except in the brain
9
Q
Cellular action of ACTH
A
- Released by pituitary
- Acts on melanocortin-2-receptor (G protein), activates AC, increases cAMP, activates PKA, increases activity of p450scc
10
Q
Cellular action of CRH
A
- Released by hypothal
- Acts on CRH receptor (G protein), activates AC, increases cAMP, activates PKA, intracellular Ca increases, ACTH released
11
Q
CRH
A
- Made in PVN of hypothalamus
- Acts on corticotroph cells
12
Q
ACTH
A
- Secreted by corticotroph cells of anterior pituitary
- Produced by post-translational processing of POMC
13
Q
Feedback inhibition of cortisol
A
- Negative feedback on ACTH and CRH
- Inhibits expression of POMC gene in anterior pit
- Decreases mRNA and peptide levels of CRH and prevents release of presynthesized CRH in the hypothal
14
Q
Post-translational processing of POMC
A
-Gives rise to ACTH and B-lipotropin
15
Q
Cushing’s syndrome
A
- Hyperadrenal function: excessive levels of cortisol for long periods of time
- Cushing’s disease: hypercortisolism secondary to excess production of ACTH from a pituitary gland adenoma
- Moon face, red face, upper body obesity, osteopenia, glucose intolerance, hypokalemia, hypertension
