Molecular Classification
Enzyme, Oxidoreductase
Other Names
3-Oxosteroid Δ4-dehydrogenase, Steroid Δ4-5α-reductase, Testosterone 5α-reductase
Disease Roles
Androgenic alopecia (male pattern baldness)Acne vulgarisBenign prostatic hyperplasia (BPH)

5-alpha reductase type I Overview

5-alpha reductase type I (5αR1) is an enzyme that catalyzes the conversion of testosterone to dihydrotestosterone (DHT) in various tissues, including the liver, skin, scalp, sebaceous glands, kidney, and brain. While it shares this function with other 5α-reductase isoenzymes, its tissue distribution and kinetic properties differ, contributing to distinct physiological roles in androgen-dependent processes, such as sebum production, hair follicle biology, and potentially neurosteroid synthesis. It is a therapeutic target for conditions like androgenic alopecia and acne.

Mechanism of Action

Inhibition of 5-alpha reductase enzyme activity, reducing the conversion of testosterone to dihydrotestosterone (DHT).

Biological Functions

Steroid metabolism
Dihydrotestosterone (DHT) production
Androgen signaling modulation

Disease Associations

Androgenic alopecia (male pattern baldness)
Acne vulgaris
Benign prostatic hyperplasia (BPH)
Altered sexual development (in deficiency states)
Insulin resistance/metabolic disorders (potential)

Safety Considerations

  • Potential impact on sexual development
  • Side effects associated with DHT reduction (e.g., sexual dysfunction)
  • Variable efficacy depending on individual isoform expression profiles

Interacting Drugs

Finasteride
Dutasteride