BCHM: Steroid Biosynthesis

Question 1

What makes up a short term stress response by adrenal glands (via catecholamines)?

Answer 1

Nerve Impulses –> catecholimines (Epi/NE)

Question 2

What makes up a long term stress response by adrenal glands (via mineralcorticoids + glucocorticoids)?

Answer 2

Steroid hormone signaling –> mineralcorticoids + glucocorticoids

Question 3

What enzyme converts cholesterol –> pregneolone?

Answer 3

desmolase

Question 4

Progesterone is the precursor for all?

Answer 4

Steroid hormones

Ex. Prgesterone, Aldosterone, Cortisol, Testosterone, Estradiol

Question 5

What positvely regulates 20,22 desmolase (AKA cytochrome P450)?

Answer 5

ACTH (adrenocorticotropic hormone)

Question 6

ACTH runs on which axis?

Answer 6

HPA (hypothalamic-pituitary-adrenal)

Question 7

What are the short term actions of ACTH?

Answer 7

stimulates lipoprotein uptake + increases availablity of cholesterol

Question 8

What are the long term actions of ACTH?

Answer 8

Stimulates the transcription of genes coding for steroid enzymes

Question 9

Cortisol binds ____________ receptor.

Function?

Answer 9

glucocorticoid receptor

increases gluconeogenesis + blood pressure

anti-inflammatory

Question 10

Why are moms who are about to give birth to premie babies given glucocorticoids?

Answer 10

During delivery, moms experience a “burst” of glucocorticoids that stimulate the production of surfactant, allowing lung expansion.

Question 11

Aldosterone binds __________.

Function?

Answer 11

Mineralcorticoid receptor

Increases salt + h20 retention

raises blood pressure

Question 12

Testosterone binds _________ receptor.

Function?

Answer 12

Androgen receptor

Male sex hormone

Question 13

Women who present w/ hirsutism (excessive body hair) + oligomenorrhea (no preiod) have what disease?

Answer 13

Congenital Adrenal Hyperplasia

Question 14

In congenital adrenal hyperplasia (CAH), what do we look for in the amniotic fluid to determine the risk of the fetus?

Answer 14

Excess cortisol precursors in amniotic fluid

Question 15

Adrenal hyperplasia can be life threatening, how do we treat it?

Answer 15

With hormone replacement therapy

Question 16

What gene mutation is responsible for 95% of Congenital Adrenal Hyperplasia patients?

Answer 16

21-hydroxylase

Question 17

What gene mutation is responsible for 5% of CAH patients?

Answer 17

11 beta - hydroxylase

Question 18

What accumulates in an 11 beta - hydroxylase mutation?

Answer 18

17 - alpha - hydroxy Progesterone

+

11 - Deoxycortiocosterone –> Hypertension

Question 19

Which enzyme causes increased Na+ absorption in the kidneys and hence produce hypertension in CAH?

Answer 19

11-deoxycorticosterone

*It also has a high affinity for the Mineralcorticoid receptor (aldosterone)

Question 20

What hormones accumulate in 21-alpha-hydroxylase deficiency of CAD?

Answer 20

Progesterone, 17 alpha - hydroxypregnolone, 17 alpa- hydroxyprogesterone

Question 21

Defects in the steroid hormone synthesis pathway cause?

Answer 21

CAH

Question 22

Which enzyme is a gateway for the sex steroids?

Answer 22

17,20 Lyase

Can cause a rare form of CAH

Question 23

Which enzyme acts as a gatekeeper to allow progesterone to get to testosterone?

Answer 23

17,20 Lyase

Have to go through this to get to sex steroids

Question 24

What is a key aspect regarding maintaining Vitamin D homeostasis in the body?

Answer 24

25-hydroxycholecalciferol is formed only in the liver.

By the 25-hydroxylase enzyme encoded by the CYP2R1 gene.