Steroids

Question 1

Where are human steroids derived?

Answer 1

From dietary steroids or from acetyl-CoA in the liver

Question 2

Where in the cell does the conversion from squalene to cholesterol take place?

Answer 2

In the ER

Question 3

How are steroids eliminated?

Answer 3

Following oxidation by cytochrome P450, most significantly in the liver ER by CYP3A4 (which introduces -OH into the steroid ring before other enzymes form bile acids)

Question 4

What is the most abundant CYP450 in the body and what % of these enzymes does it make up?

Answer 4

CYP3A4 (28% of total CYPs)

Question 5

How does the steroid-receptor complex induce changes in gene expression?

Answer 5

Via binding to Hormone Response Element (which then binds to the DNA)

Question 6

What is the difference in terms of the cellular targets of the sex steroids vs. the glucocorticoids and mineralocorticoids?

Answer 6

Sex steroids bind to a nuclear receptor in the nucleus
Glucocorticoids and mineralocorticoids bind to a nuclear receptor in the cytoplasm, which causes the receptor to lose its heat shock proteins and become active; it then migrates into the nucleus

Question 7

What is cyproterone acetate? What is it used to treat?

Answer 7

A synthetic steroid inhibitor of the nuclear androgen receptor
Used to treat hirsutism in females, prostate cancer, BPH, priapism and hypersexuality (chemical castration), as well as in hormone therapy for male-to-female gender transition

Question 8

What does the adrenal cortex produce more of: mineralocorticoids or glucocorticoids?

Answer 8

Glucocorticoids (100x)

Question 9

What other 2 steroid hormones have mineralocorticoid function, besides aldosterone?

Answer 9

Progesterone

Deoxycorticosterone