Endocrine 12: Mineralocorticoids (aldosterone) + Adrenal Androgens & Estrogens

Question 1

Origin of Mineralocorticoids

Answer 1

Zona glomerulosa of Adrenal cortex

Question 2

Nature & Chemistry of Mineralocorticoids

Answer 2

• Steroid in nature
• Main precursor is Cholesterol esters

Question 3

Which hormone has stronger bind to their protein, Aldosterone or Cortisol

Answer 3

Cortisol

Question 4

Metabolism of mineralocorticoid

Answer 4

90% is reduced & conjugated by liver with glocuronic acid & then exerted in urine

Question 5

Mechanism of Action of Aldosterone

Answer 5

1. Diffuses through lipid cell membrane
2. bind to specific cytoplasmic receptor protein, forming aldosterone-receptor complex
3. A-R complex diffuses into nucleus and induces the transcription of different types of mRNA

Question 6

general effect of Aldosterone

Answer 6

⬆️Na+, ⬆️water, ⬇️K+, ⬇️H+

Question 7

Main goal for aldosterone

Answer 7

to maintain ECF volume by conserving body sodium & increasing its reabsorption in the kidney

Question 8

Describe effect of Aldosterone on the kideny

Answer 8

Increases Na+ reabsorption:
* Induce Na+ channels to be inserted in Luminal broder of P cells
* Increase Number of open epithelial Na+ channels
* Increase Na+ K+ ATPase pump at the basolateral border

Increase Active secretion of K+

Increases water reabsorption

Increase H+ secretion

Question 9

Enumerate factors affecting Aldosterone secretion

Answer 9

• RAAS
• Plasma K+ levels
• Plasma Na+
• ACTH (tonic role)

Question 10

explain how RAAS contributes to Aldosterone secretion

Answer 10

1. under certain changes, juxtaglomerular cells secrete renin enzyme
2. Renin acts on Angiotensinogen –> Angiotensin I
3. Angiotensin I is converted into Angiotensin II by ACE
4. Angiotensin II stimulates Zona glomerulosa —> Hypertrophy + increase in Aldosterone synthesis (early: Cholesterol to preganolone, Late: Corticosterone to Aldosterone)

Question 11

Enumerate stimuli increasing Renin secretion from juxtaglomerular cells

Answer 11

• Hyponatremia (⬇️Na+)
• Hypovolemia/ hemorrhage (⬇️H2O)
• Sympathetic Activity
• keeping upright posture for long time

Question 12

Factor inhibiting renin secretion

Answer 12

ANP (Atrial Naturetic peptide)

Question 13

Explain how plasam K+ levels affect Aldosterone secretion

Answer 13

• Increased K+ stimulates conversion of Cholesterol to pregnanolone & Corticosterone to Aldosterone
• Increased K+ depolarizes Adrenal cell —> open of Voltage gated Ca2+ channels –> increase intracellular Ca2+ —> release of Aldosterone by the cell

Question 14

Adrenal sex hormone are released from ____

Answer 14

Zona reticularis

Question 15

Enumerate Adrenal Androgens

Answer 15

• DHEA
• Androstenedione

Question 16

Physiological function of Adrenal Androgens in Female & Male

Answer 16

Female:
* Maintain normal pubic & Axillary hair
* Stimulate RBCs production
* (no musculinizing effect)

Male: No physiological importance