Steroid Hormone Synthesis

Question 1

……is the precursor of all steroid hormones has…..C

Answer 1

Cholesterol
27

Question 2

……..is the rate-limiting step of synthesis of ALL steroid found in……..belongs to……requires…..
Coverts….to….

Answer 2

20-22 lyase/desmolase enzyme
Inner mitochondrial membrane
CYP450
NADPH & molecular O2
Cholesterol/pregnenolone

Question 3

Cholesterol move to mitochondria by……

Answer 3

Steroidogenic acute regulatory protein (STAR)

Question 4

Pregnenolone is conveted to progesterone by……

Answer 4

3b hydroxysteroid dehydrogenase

Question 5

Describe synthesis of adrenal androgens

Answer 5

Pregonolne & progesterone are hydroxylated by 17-a-hydroxylase
C17-C20 lyase enzyme catalyzes cleavage of 2-carbon side-chain of these compounds at C17 to form 19C adrenal androgens DHEA & andronstendione which are weak androgens

Question 6

Describe activation reaction of testosterone

Answer 6

Converted to its active form dihydrotetstosetrone in target cells by reduction of its ring A by 5-a-hydroxylase enzyme forming DHT.

Question 7

The enzyme which converts testosterone to estradiol is……

Answer 7

Aromatase (one of P450)

Question 8

Describe pathway for cortisol synthesis

Answer 8

1.17-a-hydroxylase acts on progesterone producing 17-a-hydroxylprogesterone which is transported to sER
2. 21-a-hydroxylase catalyzes hydroxylation of C21 forming 11-deoxycortisol
3. 11-deoxycortisol is transported to mitochondria where 11-a-hydroxylase forms cortisol

Question 9

Describe pathway for aldosterone synthesis

Answer 9

1. Progesterone is hydroxylated at C21 by 21-a-hydroxylase forming deoxycorticosterone
2. 11-a-hydroxylase convert DOC to corticosterone
3. Terminal step is by P450 aldosterone system (aldosterone synthase) in mitochondria

Question 10

Synthesis of estradiol is activated by……., testosterone by……,cortisol by……

Answer 10

FSH
LH
ACTH

Question 11

Mention stimuli for aldosterone production

Answer 11

1. Ang II, hyperkalemia, hyponatremia
2. ACTH allows cells to respond optimally to Ang II (Permissive action)

Question 12

Most common type of CAH is….., while rare type is…..

Answer 12

21-hydroxylase def
3b-hydroxysteroid dehydrogenase

Question 13

Describe the presentation & ttt of 21-hydroxylase def

Answer 13

Inc sex hormones (musculinization of female genitalia at birth, precocious puberty in both sexes)
Dec cortisol & mineralocorticoids
ACTH inc & diffuse skin pigmentation
TTT: Glucocorticoid & mineralocorticoid

Question 14

Describe presentation of 3b-hydroxysteroid dehydrogenase def

Answer 14

Dec sex hormones (female genitalia-like in male at birth, puberty delay in both sexes)
Dec cortisol & mineralocorticoids
ACTH inc & diffuse skin pigmentation

Question 15

Describe presentation of 17-a-hydroxylase def

Answer 15

Dec sex hormones (female genitalia-like in male at birth, puberty delay in both sexes)
Dec cortisol & inc mineralocorticoids (hypernatremic hypokalemic HTN)
ACTH inc & diffuse skin pigmentation

Question 16

Mention an application of steroid H synthesis in cancer treatment

Answer 16

Aromatase inhibitors are used in treatment of estrogen-responsive breast cancer in postmenopausal women, causing arrest of tumor growth &/or initiation of apoptosis