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#endocrinology

3 public questions tagged with this topic.

Sex determination-l

Which hormone converts testosterone into dihydrotestosterone (DHT)?

Conversion of testosterone into more potent dihydrotestosterone responsible for external genital masculinization is catalyzed not by hormone but by membrane enzyme steroid 5α-reductase type 2 encoded by SRD5A2 gene. Enzyme localized in genital skin, prostate and hair follicles uses NADPH to reduce testosterone double bond forming DHT. DHT binds androgen receptor with higher affinity and slower dissociation ensuring robust activation of male morphogenetic genes. Confusing hormone with enzyme is common, but catalytic step essential. In provided options intended catalyst for external genitalia virilization corresponds to 5α-reductase activity.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 17: 5α-reductase converts testosterone to DHT.

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Cell Signaling ELR Pathways - I

Major IRS proteins involved in insulin signaling are:

IRS-1 and IRS-2, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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