Disorders of Adrenal cortical function & Mineralcorticoids

Question 1

Role & mechanism of Aldosterone

Answer 1

Role: reabsorbs Na & H2O in blood
Mechanism: Renin-angiotensin system: aldosterone binds to mineral corticoid receptor (MR) & activates eNAC (epithelial Na Channel) in DCT => Na reabsorption (K+ excretion) = Inc osmolality = inc water retention (= inc ADH by angiotensin II)

Question 2

Describe the Renin-Angiotensin system for regulation of aldosterone

Answer 2

S: Dec renal blood flow
1. Cells in juxtaglomerular apparatus release Renin (enz)
2. Renin cleaves angiotensinogen to angiotensin I
3. Angiotensin converting enzyme (ACE) cleaves this to Angiotensin II
4. Stimulates secretion of aldosterone from Adr. cortex
R: Na & H2O reabsorption
F: Inc. circulating vol. = -ve feedback

Question 3

list 2-3 other factors that stimulate aldosterone secretion

Answer 3

1. Hi Plasma K+ (hyperkalemia)
2. Low BP detected by baroreceptors (hypovolemia) => stimulate renin
3. ACTH has small influence

Question 4

Conn’s syndrome (1 hyperaldosteronism)

Answer 4

• Hi aldosterone secreted =low renin, Hi ald:ren ratio

- Hypertension due to Hi Na, *Lo K+, Lo H+, *Hi HCO3-

Question 5

Bartter’s syndrome (2 hyperaldosteronism) cause & manifestation

Answer 5

• defect in thick ascending LOH = dec Na & Cl reabsorp. & not respond to ADH = alsway hypovolemia
• Polyuria & dipsia
• Hi renin, Hi Aldosterone,

Question 6

Liddle’s syndrome (pseudohyperaldosternosim) cause & manifestation

Answer 6

Due to mutaion in eNAC = Na reabsorp & K loss (not controlled by aldosterone)

• low aldosterone & lo renin
• Hypertension & Lo K

Question 7

Cushings syndrome (1 hypercortilism) cause & manifestation

Answer 7

Inc cortisol secretion. 
(High activity of Enzyme > breakdown Cortisol to cortisone)
- Low K+/ Hi HCO3-, Hi Na & water
- hypertension
- hyperglycemia, hyperlipidemia

Question 8

Addison’s syndrome (1 hypocortilism) cause & manifestation

Answer 8

• Damaged Adr. cortex
  => low Cortisol & aldosterone
• HypOtension due to Lo Na, *HiK+, Hi H+, *Lo HCO3-

Question 9

Congenital adrenal hyperplasia (CAH) cause & manifestation

Answer 9

• 11beta hydroxylase deficiencies => Hi 11-deoxycorticosterone = Hi cortiol & aldosterone (*not destruction of Adr. cortex)
• caused by Inc ACTH => hyperplasia of adrenal glands = Hi Aldosterone, cortisol, adrenal androgens

Question 10

DX method for Addison’s syndrome

Answer 10

Dx w/ synacthen stimulation test

Question 11

Lab Ix of Congenital adrenal hyperplasia (CAH)

Answer 11

• **Plasma 17-OH-progesterone OR it’s pregnanetriol (it’s urine metabolite)
• Androgens
• ACTH