Steroid Biosynthesis Flashcards
5 steroid hormone classes
Progestins Glucocorticoids Mineralocorticoids Estrogens Androgens
Progesterone is an example of the ______ hormone class.
Where is it synthesized, distributed, and what does it mediate?
Progestins
Synthesized in adrenal glands, ovaries, testes
Distributed to uterus
Mediates implantation and maintenance of pregnancy
Cortisol, cortisone, and corticosterone are examples of what class of hormone?
Where are they synthesized, distributed, and what do they mediate?
Glucocorticoids
Synthesized in adrenal glands
Distributed to many tissues/organs; increases BP and Na uptake in kidneys; mediates response to stress by increasing protein catabolism and gluconeogenesis and reducing inflammation
Aldosterone and 11-deoxycorticosterone are members of what hormone class?
Where are they synthesized, distributed, and what do they mediate?
Mineralocorticoids
Synthesized in adrenal glands
Distributed to kidney tubules, colon, parotid gland
Increases Na/H2O retention, K excretion, and BP
Estradiol and estrone are members of ______ hormone class
Where are they synthesized and distributed, and what do they mediate?
Estrogens
Synthesized in ovaries, placenta, adipose tissue
Distributed to primary and secondary reproductive organs
Mediate feminization, estrous cycle, inhibit testosterone synthesis
Testosterone, 5-alpha-dihydrotestosterone, and DHEA are members of what hormone class?
Where are they synthesized and distributed and what do they mediate?
Androgens
Synthesized in adrenal glands, ovaries, and testes
Distributed to primary and secondary reproductive organs and muscle
Mediate spermatogenesis, secondary male characteristics, bone maturation, and virilization
Cholesterol fate in liver
Used to synthesize bile acids
Cholesterol fate in adrenal glands, ovaries, and testes
Synthesize steroid hormones
Cholesterol fate in skin
Used to synthesize vit D
What are the main lipophilic ligands?
Steroid hormones
Fat-soluble vitamins = ADEK
Are growth factors hydrophilic or lipophilic ligands?
Hydrophilic
Precursor/starting material to cholesterol synthesis
Sterane ring
What are some examples of cholesterol-based lipophilic signaling molecules/ligands?
Cortisol Estradiol Thyroxine Testosterone Vitamin D3 Retinoic acid (makes Vit A)
T/F: most signaling molecules are hydrophobic and readily diffuse across the membrane
False, most are hydrophilic and require cell surface receptors
Would you classify steroid signaling as fast or slow responses?
Slow - because most of them initiate or repress gene expression which takes time
Steroid hormones are synthesized from cholesterol in the smooth ER of the adrenal cortex, ovaries, and testes
Where do these tissues obtain cholesterol?
Circulating LDL
De novo synthesis from acetyl CoA
Cholesterol esters stored in cytoplasmic lipid droplets
Which of the following requires the most 5-carbon IPP units to synthesize?
A. Vitamin A B. Vitamin D C. Vitamin E D. Vitamin K E. Vitamin B
B. Vitamin D
Requires 6 IPP units, while vit A, E, and K require 4. Vitamin B is water soluble
The synthesis of steroid hormones begins with the RATE-LIMITING step catalyzed by ________, an enzyme that incorporates a carbonyl group on the D ring of cholesterol and cleaves off a 6-carbon piece of its side chain to form ____________
Desmolase
Pregnenolone
The rate limiting step of steroid hormone synthesis (the conversion of cholesterol to pregnenolone via RL enzyme desmolase) MUST be regulated. What is an important positive regulator of desmolase?
ACTH
Pregnenolone is an alcohol that acts as a modulator of NT signaling in the brain without being converted to other steroids. It affects the NMDA glutamate receptor involved in memory and learning.
Pregnenolone must be converted to _______ for synthesis of other proestrogens, this is done with enzymes _______ and __________
Progesterone
17-alpha-hydroxylase
3-beta-hydroxysteroid dehydrogenase
Once pregnenolone is converted to progesterone via 17-alpha-hydroxylase and 3-beta-hydroxysteroid dehydrogenase, what are the possible end products of steroid hormone synthesis?
17-alpha hydroxylase is involved in multiple arms of the steroid hormone synthesis pathway, so possible outcomes include:
Mineralocorticoids
Glucocorticoids
Estrogens
Androgens
What is unique about glucocorticoids as they relate to mineralocorticoids, and how do they compare to mineralocorticoids in terms of concentration?
Glucocorticoids have affinity for mineralocorticoid receptors and are 100 times more concentrated than mineralocorticoids
Which of the following is progesterone specifically converted to in a tissue specific manner?
A. Aldosterone in the adrenal cortex
B. Cortisol in the adrenal cortex
C. Estradiol from testosterone precursor in the ovaries
D. Testosterone and dihydrotestosterone in testes
E. All of the above
E. All of the above