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Questions and Answers
Which enzyme catalyzes the irreversible conversion of testosterone to dihydrotestosterone (DHT)?
In adult males, the plasma concentration of DHT is approximately what fraction of the testosterone concentration?
Which tissues have receptors sensitive to DHT rather than testosterone?
What type of reaction converts pregnenolone to testosterone, apart from those catalyzed by 17β-HSD?
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Where does the synthesis of testosterone from pregnenolone primarily occur?
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From which hormone is estradiol (E2) primarily produced in small amounts?
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Study Notes
Testosterone Synthesis
- Reactions involved in testosterone synthesis from pregnenolone are irreversible, except for those catalyzed by the 17β-OHSD enzyme.
- These reactions occur in the smooth endoplasmic reticulum.
Related Hormones
Dihydrotestosterone (DHT)
- Produced from testosterone in an irreversible reaction catalyzed by NADPH-dependent 5α-reductase enzyme.
- Mainly produced in extratesticular tissue and to a lesser extent in the testes.
- Plasma concentration of DHT in adult males is about one-tenth that of testosterone.
- Testosterone is considered a prohormone since it's converted into the more potent DHT.
- Some receptors in the body are sensitive to testosterone (spermatogonia, brain, kidney, muscle, and bone), while others are sensitive to DHT (prostate, external genitalia, and genital skin).
Estradiol (E2)
- Produced in small amounts mainly from testosterone.
Anti-Mullerian Hormone (AMH)
- Produced by the Sertoli cells of the testes.
- Production starts in males during early embryonic life.
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Description
This quiz covers the reactions involved in testosterone synthesis from pregnenolone, including the role of 17β-OHSD enzyme, and the production of dihydrotestosterone (DHT) from testosterone. It also touches on the plasma concentration of DHT and its production sites.
