Steroid Hormone Biosynthesis

Question 1

Major steroidogenic tissues

Answer 1

Adrenals-glucocorticoids, mineralcorticoids, androgens
Gonads-testis/ovaries
Placenta

Question 2

Cholesterol role in steroidogenesis

Answer 2

steroid backbone; ring structure conserved

Question 3

Rate Limiting Step for cholesterol production

Answer 3

HMG CoA–>mevalonate

• enz: HMG CoA reductase
• where statin drugs act

Question 4

Rate Limiting step in steroidogenic pathway

Answer 4

Cholesterol–>Pregnenolone+icosaproaldehyde

enz: Mitochondrial p-450 scc
- needs NADPH

Question 5

action of mito p450 scc enzyme

Answer 5

cleaves side chain

Question 6

PKA regulates

Answer 6

cholesterol synthesis

Question 7

StAR protein action

Answer 7

shuttles cholesterol to p 450 in mitochondria

Question 8

17 alpha Hydroxylase

Answer 8

in ER

pregnenalone shuttled to ER and hydroxylated at C17

Question 9

3-beta Dehydroxylase

Answer 9

in ER

conversion of OH on pregnenalone to a keto group (on C3)

Question 10

21 Hydroxylase

Answer 10

in ER (downstream from pregnenalone)
hydroxylates free methyl group to OH at C21

Question 11

11 beta Hydroxylase

Answer 11

in mito! (further downstream from pregnenalone)

hydroxylates methyl to OH on C11 on cholesterol backbone

Question 12

Adrenal cortex 3 parts

Answer 12

zona glumerulosa, zona fasciculata, zona reticularis

Question 13

zona glumerulosa

Answer 13

outermost region; synthesizes aldosterone (a mineralcorticoid)

Question 14

zona fasciculata

Answer 14

middle region (largest); synthesizes cortisol (a glucocorticoid)

Question 15

zona reticularis

Answer 15

innermost region; synthesizes Androgens (mainly DHEA)

Question 16

DHEA is precursor to

Answer 16

sex hormones

Question 17

11 beta hydroxylase produces

Answer 17

corticosterone and cortisol

Question 18

Aldosterone synthase rxn

Answer 18

corticosterone–>aldosterone

Question 19

17,20 lyase reaction

Answer 19

prenenolone–>DHEA

Question 20

3 beta HSD reaction

Answer 20

DHEA–>Androstenedione

Question 21

Congenital Adrenal Hyperplasia

Answer 21

defect in production of cortisol

Question 22

21 alpha hydroxylase deficiency (CAH)

Answer 22

reduced production of corticosterone, aldosterone, and cortisol
overproduction of Androstenedione

Question 23

11 alpha hydroxylase deficiency (CAH)

Answer 23

reduced production of corticosterone, aldosterone, and cortisol
overproduction of Androstenedione

Question 24

17 alpha hydroxylase deficiency (CAH)

Answer 24

reduced production of Androstenedione, and cortisol

overproduction of aldosterone

Question 25

defect in StAR associated with

Answer 25

CAH