Steroid Biosynthesis Flashcards
What regulates cholesterol desmolase activity?
ACTH
What does cholesterol desmolase do?
converts cholesterol to pregnenolone (committed step)
What tissues is cholesterol desmolase found in? (4)
- adrenals
- testes
- ovary
- placenta
All steroid-producing tissues!
What is the most important biochemical intermediate?
pregnenolone
What role does progesterone play in pregnancy? (correlation box)
- It regulates voltage-gated Ca2+ channels on spermatozoa
- prepares uterus for implantation
- causes smooth muscle relaxation
- decreases maternal immune response
basically supports pregnancy, and decreases prior to menstruation, labor, and lactation
How are glucocorticoids and infant respiratory distress syndrome related (IRDS)? (correlation box)
- normally burst of glucocorticoids prior to birth causes production of surfactant
- preemie’s don’t have this, get IRDS unless glucocorticoids given to mother before birth
Metabolic modulation of steroid hormones is important for what? (correlation box)
- Not OD’ing yourself on mineralocorticoids or glucocorticoids
- changes affinity of hormone for receptor so you don’t get overeffect (like too much Na/H20 retention)
What globulin is progesterone carried on? (correlation box)
CBG (corticosteroid-binding globulin)
How does cortisol suppress the immune system? (correlation box)
It inhibits the transcription factor that activates NF-KB, inhibiting B cell response and apoptosing T cells.
What disorders are associated with vitamin D? Why? (correlation box)
- brittle bones/ rickets in kids
- osteomalacia / several fx’s in adults
What can adrenal hyperplasia cause in women? (3)
- hirsutism
- general oligomenorrhea
- infertility
What is adrenal hyperplasia caused by? (2)
- deficiencies in the adrenal enzymes used to synthesize corticosteroids
- increased production from adrenal gland of both cortisol precursors and androgens
What two enzyme deficiencies can cause adrenal hyperplasia?
- 21 hydroxylase
- 11-beta hydroxylase
What does a 21 - hydroxylase deficiency result in a buildup of? (2)
- progesterone
- 17-hydroxyprogesterone
What is another name for 21 - hydroxylase?
CYP21A2
What does a 11-beta hydroxylase deficiency result in a buildup of? (2)
- deoxycorticosterone
- 11-deoxycortisol
What is another name for 11-beta hydroxylase?
CYP11B1
What can a deficiency of CYP11B1 result in, physiology-wise?
- hypertension and high testosterone, because 11-deoxycorticosterone can act as a ligand in the aldosterone pathway
What can a deficiency of CYP21A2 result in, physiology-wise?
- low blood pressure and high testosterone, because progesterone CAN’T act as a ligand, and you get no aldosterone effect
What is primary aldosteronism also known as?
Conn’s syndrome
What does aldosterone do?
Promotes excretion of H+ and K+
What are the symptoms of Conn Syndrome? (4)
- excessive aldosterone secretion
- retention of sodium
- loss of potassium
- hypertension
What hormones increase sodium retention? (5)
- aldosterone
- 11-deoxycorticosterone
- testosterone
- cortisol
- cortisone
What is the physical manifestation of 11 - beta hydroxylase deficiency?
- virilization
How do tumor cells affect cortisol production?
- they cause its release in the absence of any ACTH stimulation
What is another name for 17, 20-lyase?
CYP17A1
What do mutations in 17, 20-lyase cause?
deficiency in androgens and estrogens
What two ways is vitamin D3 obtained?
- absorbed through intestine as ergocalciferol
- converted from 7-dehydrocholesterol in the skin
Where is 25-hydroxycholecalciferol found?
in the liver exclusively
What is the pathway of Vitamin D3 synthesis?
cholecalciferol → 25-hydroxycholecalciferol → 1,25-dihydroxycholecalciferol
What enzyme converts cholecalciferol to 25-hydroxycholecalciferol?
25-hydroxylase
What enzyme converts 25-hydroxycholecalciferol to 1,25-dihydrocholecalciferol?
1-alpha-hydroxylase
Where does the final step of Vit D3 synthesis occur?
kidney
