Steroid Biosynthesis - 2/1 Theisen

Question 1

What is responsible for stimulating the production of surfactant in neonates?

Premature babies develop what due to the lack of this hormone?

Answer 1

Glucocorticoids

Infant respiratory distress syndrome

Question 2

Cortisol is converted to cortisone with what enzyme?

What can inhibit this enzyme?

Causing what?

Answer 2

11-Beta-hydroxysteroid dehydrogenase

Licorice bc it has isoflavones

Hypertension due to salt retention

Question 3

What enzyme converts testosterone to DHT?

What can inhibit this enzyme

What is the inhibitor used to treat?

Answer 3

5alpha-Reductase

Finasteride

Baldness, benign prostatic hyperplasia

Question 4

What hydrophobic molecules can cross the CM and get into the cytoplasm?

Answer 4

O2, CO2, N2

Steroid hormones

Question 5

Where are steroid hormones synthesized from cholesterol in the body?

Where do these tissues get cholesterol from?

Answer 5

SER of adrenal cortex, ovaries, testes

Circulating LDL, de novo from acetyl CoA or cholesterol esters

Question 6

What is the 1st step in steroid hormone synthesis?

What enzyme is used?

How is the starting product modified?

Answer 6

Cholesterol -> pregnenolone

Desmolase (RLS)

Adds a C=O and cleaves 6C off side chain

Question 7

What stimulates the conversion of cholesterol to pregnenolone?

Answer 7

ACTH

Question 8

The conversion of pregnenolone to progesterone requires what enzyme?

Answer 8

3-Beta-hydroxysteroid dehydrogenase

Question 9

The conversion of pregnenolone to 17-alpha-Hydroxypregnenolone requires what enzyme?

Answer 9

17-alpha-hydroxylase

Question 10

Progesterone is converted into aldosterone where?

Cortisol where?

Estradiol where?

Testosterone where?

Answer 10

Adrenal cortex ZG

Adrenal cortex ZF

From testosterone in ovaries

From DHT in testes

Question 11

Where is desmolase found?

What family is it from?

Answer 11

Gonads and adrenal cortex

P-450, monoxide base

Question 12

When is ACTH secreted?

From where?

What does it stimulate?

Answer 12

Stressful conditions (hypoglycemia, cold, exercise)

From pituitary gland

Release of cortisol from adrenals

Question 13

What else will increase the activity of desmolase?

Answer 13

LH

Question 14

What stimulates estradiol production in the ovaries?

What enzyme does this activate?

Answer 14

FSH

Aromatase

Question 15

What inhibits the production of GnRH from the hypothalamus?

Answer 15

Progesterone

Question 16

In males what inhibits FSH?

LH?

Answer 16

Inhibin

Testosterone

Question 17

In females, what inhibits the production of FSH and LH from the pituitary gland?

Answer 17

Progesterone

Estradiol (early-mid follicular phase)

Question 18

In females what stimulates the formation of FSH and LH from the pituitary gland?

Answer 18

Estradiol (late follicular phase)

Question 19

What does FSH and LH make in the ovaries?

Answer 19

Estradiol

Progesterone

Question 20

A defect in what enzyme will cause deficiencies in mineral and glucocorticoids?

Answer 20

21-hydroxylase

Question 21

21-hydroxylase defects leads to what?

Specifically what in females?

Answer 21

Hyponatremia, hypotension, hypoglycemia

Virilism due to INC flow of intermediates into adrenal androgens

Question 22

Deficiency in 17-a-hydroxylase causes what?

Answer 22

Loss of cortisol and sex steroids

Dec in cortisol is compensated by corticosterone

Question 23

Defects in 11-B-hydroxylase cause what?

Answer 23

Hypertension due to accumulation of 11-deoxycorticosterone

Question 24

Aldosterone is made from what? Where?

Excessive levels Cause what?

Answer 24

Progesterone, in adrenal cortex (zona glomerulosa)

Conn syndrome - INC BP, HTN, hypernatremia

Question 25

What is Cushing syndrome caused by? Characteristics?

Answer 25

Too much cortisol Excess fat on face and trunk

Question 26

How are glucocorticoids and progesterone transported in the blood? Testosterone, DHT, estradiol carried by what? Where are these carrier proteins made?

Answer 26

CBG SHBG Liver

Question 27

What are the effects of ADH?

Answer 27

Vasoconstriction, stimulates thirst, INC water retention

Question 28

What causes immunosuppression by inhibiting cellular and humoral responses? How?

Answer 28

Glucocorticoids and cortisol Induce I-Kba which sequesters NF-KB in its inactive form in the cytoplasm

Question 29

What else can cortisol cause via immene suppression?

Answer 29

T-cell apoptosis

Question 30

Too little Vitamin D causes what? Too much?

Answer 30

Rickets, osteomalacia, hypocalcemic tetany Hypercalcemia/calciuria -> dazed appearance, no appetite, sarcoidosis (granulomas in skin, lungs, LNs)

Question 31

What is the active form of Vit D?

Answer 31

Calcitriol (1,25-dihydroxycholecalciferol)

Question 32

Is Vit D classified as a steroid? How does it act?

Answer 32

NO Binding to nuclear receptors and altering the expression of target gene containing VDRE

Question 33

What enzyme helps to form active Vit D after UV exposure to the skin?

Answer 33

7-dehydrocholesterol

Question 34

In intestinal cells what does Vit D come from?

Answer 34

Ergocalciferol (Vit D2)

Question 35

What enzyme in the liver is needed in Vit D synthesis? Kidney?

Answer 35

25-hydorxylase 1-alpha-hydroxylase

Question 36

1-alpha-hydroxylase can be activated by what? inactivated by what?

Answer 36

PTH, low PO4 Calcitriol

Question 37

What does Calcitriol increase? What does it stimulate? Inhibit?

Answer 37

Ca reabsorption from intestine, kidneys, and bone PTH Calcitonin

Question 38

What is responsible for regulating VG Ca2+ channels on sperm, prepares the uterus for implantation, causes smooth m. Relaxation and DEC mother's immune response? Dec in this hormone precedes what?

Answer 38

Progesterone Menstruation, labor, lactation