5 -Reductase

5_-Reductase

5_-Reductase is an enzyme that plays a crucial role in the metabolism of steroids within the human body. It is responsible for the conversion of testosterone into dihydrotestosterone (DHT), a more potent androgen. This enzyme is significant in various physiological processes and is implicated in several medical conditions.

Function

5_-Reductase catalyzes the reduction of the double bond in the A-ring of testosterone, converting it into dihydrotestosterone. DHT is a key androgen that binds to androgen receptors with greater affinity than testosterone, leading to more pronounced androgenic effects. This conversion is essential for the normal development of male characteristics and reproductive organs.

Isoenzymes

There are three isoenzymes of 5_-Reductase, each encoded by different genes and with distinct tissue distributions:

• Type 1 (SRD5A1): Predominantly found in the liver and skin.
• Type 2 (SRD5A2): Primarily located in the prostate, seminal vesicles, and hair follicles.
• Type 3 (SRD5A3): Recently identified and less well understood, but present in various tissues.

Clinical Significance

5_-Reductase is involved in several medical conditions due to its role in DHT production:

• Benign prostatic hyperplasia (BPH): An enlargement of the prostate gland, often treated with 5_-reductase inhibitors to reduce DHT levels and alleviate symptoms.
• Androgenetic alopecia: Commonly known as male pattern baldness, this condition is linked to DHT's effects on hair follicles.
• Prostate cancer: DHT is implicated in the growth of prostate cancer cells, and inhibitors of 5_-reductase are sometimes used in treatment.
• Congenital adrenal hyperplasia: A condition that can involve abnormal steroid metabolism, where 5_-reductase activity may be relevant.

Inhibitors

5_-Reductase inhibitors are drugs that block the action of the enzyme, thereby reducing the conversion of testosterone to DHT. Common inhibitors include:

• Finasteride: Primarily inhibits type 2 5_-reductase and is used in the treatment of BPH and androgenetic alopecia.
• Dutasteride: Inhibits both type 1 and type 2 isoenzymes and is used for similar indications as finasteride.

Related Pages

• Testosterone
• Dihydrotestosterone
• Androgen receptor
• Steroid metabolism
• Benign prostatic hyperplasia
• Androgenetic alopecia