HPO/HPA Axis

Question 1

synthesis of adrenal steroids

Answer 1

cholesterol (ZG) > pregnenolone (ZG)>

1. (17a-hydroxylase) > 17-OH pregnenolone (ZF)
2. progesterone (ZG) > (17a-hydroxylase) > 17-OH progesterone (ZF)

Question 2

pathophys of 17a-hydroxylase deficiency

Answer 2

• stops conversion of pregnenolone or progesterone to their 17 hydroxy(OH) forms
• cholesterol > pregnenolone > progesterone and downstream will inc aldosterone
• all within ZG > INC mineralocorticoids (DEC cortisol/sex hormones)

Question 3

17a-hydroxylase deficiency clinical characteristics

Answer 3

• inc aldosterone > inc BP and dec K due to effects on kidney
• atypical genetalia/undescended testes
• lack of secondary sexual development

Question 4

only pathway able to move forward in 17a-hydroxylase deficiency

Answer 4

progesterone (ZG)

(21 hydroxylase)

11-deoxycorticosterone (ZG)

(11B-hydroxylase)

corticosterone (ZG)

aldosterone (ZG)

Question 5

cortisol/cortizone synthesis

Answer 5

17-hydroxyprenenolone (ZF)

17 hydroxyprogesterone (ZF)

(21 hydroxylase)

11-deoxycortisol (ZF)

(11B-hydroxylase)

cortisol (ZF)

cortisone (ZF)

Question 6

pathphys deficiency of 21-hydroxylase

Answer 6

• stops conversion of progesterone > 11 deoxycorticosterone and conversion of 17OH progesterone > 11 deoxycortisol
• 17 OH pregnenolone and progesterone > DHEA and aldrostenedione > inc sex hormones
• all within ZR > INC androgens (dec glucocorticoids and mineralcorticoids)

Question 7

clinical characteristics deficiency of 21-hydroxylase

Answer 7

• BP dec and K inc (opp os 17ahydroxylase def)
• salt wasting

Question 8

pathophys 11B-hydroxylase deficiency

Answer 8

• stops conversion of 11dexoycorticosterone > corticosterone and conversion of 11deoxycortisol > cortisol
• 17 OH pregnenolone and progesterone > DHEA and aldrostenedione > inc sex hormones
• all within ZR > INC androgens (dec cortisol and aldosterone)

Question 9

clinical characteristics 11B-hydroxylase deficiency

Answer 9

• dec K, less renin (due to INC BP)
• severe HTN in childhood

Question 10

why is there inc BP in 11B-hydroxylase deficiency?

Answer 10

bc 11-deoxycorticosterone (which cant be converted) causes BP inc (aldosterone like effect)

elevated BP with LOW potassium but DEC ALDOSTERONE

Question 11

DHEA synthesis

Answer 11

17 hydroxypregnenolone (ZF)

DHEA (ZR)

DHEA-s (ZR)

Question 12

testosterone/estrogen synthesis

Answer 12

17 hydroxypregnenolone (ZF) >

1. 17-hydroxyprogesterone (ZF) >
2. DHEA (ZR) >

androstenedione (ZR) >

1. testosterone (ZR) >
2. estrone (PT) >

estradiol (PT)