Steroid Hormones

Question 1

What endocrine glands secrete steroid hormones?

Answer 1

Adrenal Cortex

Testes

Ovaries

Placenta

Question 2

What is the principal source of cholesterol for steroidogenesis?

Answer 2

Low-density Lipoprotein

Question 3

What is the role of cholesterol esterase?

Answer 3

Allows steroidogenic cells to mobilize cholesterol esters

Question 4

What is the first step of steroid hormone synthesis?

Answer 4

Conversion of cholesterol to pregnenolone

Catalyzed by P450scc

Question 5

What is the rate-limiting step of the biosynthesis of steroids?

Answer 5

The transfer of cholesterol to the inner mitochondrial membrane

This is due to the fact that cholesterol availability limits the activity of P450scc

Question 6

What is the function of steroidogenic acute regulatory protein (StAR)?

Answer 6

Facilitates the movement of cholesterol from the outer mitochondrial membrane to the inner mitochondrial membrane

Synthesis induced by a cAMP-dependent mechanism

Question 7

What dictates the specific steroidal products produced from pregnenolone?

Answer 7

Which steroidogenic enzymes are expressed by that tissue

Synthesis of some hormones can involve more than one cell type

(Adrenal, gonadal, placental)

Question 8

Describe the release of steroid hormones.

Answer 8

There are no special mechanisms for the storage of newly synthesized steroid hormones

So, steroidogenic cells release steroid hormones as soon as they are synthesized

Question 9

How do tropic hormones mobilize stored cholesterol?

Answer 9

Stimulating cholesterol esterase activity

Inhibiting acyltransferase activity

Question 10

What are the three specific binding proteins for steroids?

Answer 10

Corticosteroid-binding globulin (CBG)

Sex steroid-binding globulin (SHBG)

Vitamin D-binding globulin

*There is also nonspecific binding to albumin

Question 11

What is the free fraction of a steroid hormone?

Answer 11

Steroid hormone that is unbound

In equilibrium with the fraction that is bound to binding proteins

Susceptible to metabolism and excretion

Question 12

Generally, how are steroid hormones metabolized and what is the principal site?

Answer 12

Humans cannot break down the steroid nucleus

So, SH’s are degraded by being converted to inactive metabolites

Principal site of steroid inactivation is the liver

Question 13

What occurs after steroid hormone inactivation?

Answer 13

Metabolites are conjugated to glucuronic acid or sulfate

Conjugation facilitates the clearance of inactivated steroid hormone by increasing their solubility in water

Question 14

How do steroid hormone receptors function?

Answer 14

Ligand-activated transcription facteors

Have a nuclear localization signal

Receptors do not bind DNA unless the hormone is bound to its appropriate binding site on the receptor

Question 15

What is the state of the steroid hormone receptor when unbound to hormone?

Answer 15

When unbound, the receptors form a large complex with chaperone proteins (HSP)

Question 16

What is a hormone response element?

Answer 16

Specific DNA sequences that allow hormone-occupied receptors to bind to target genes

Question 17

When does activation or repression of gene transcription occur?

Answer 17

When steroid hormone-bound receptor dimers recruit a complex of coactivator proteinns

In repression, the dimers recruit corepressor proteins