Anti-Androgens

What is an androgen?

Androgen is a generic term for male hormones which are steroid hormones that bind to the androgen receptor and control the development of male characteristics.  The main androgen is testosterone, which is converted to its active and more potent metabolite dihydrotestosterone (DHT) by the action of the enzyme 5-alpha reductase and.  Both testosterone and DHT bind to the androgen receptor within responsive cells of various tissues including brain, bone, hair follicles, testes and prostate cells.  

What is an anti-androgen?

Anti-androgens are drugs that counteract or block the biological effects of the male hormone testosterone or its active metabolite DHT on a wide range of tissues where they normally have biological activity.  They are usually steroidal and fat soluble and pass through the cell membrane to interact with the androgen steroid receptors inside the cell and compete with testosterone or DHT for these receptors.  This blocks expression of genes involved in the development and maintenance of male characteristics. 

Some anti-androgens are non-steroidal and also compete with testosterone and DHT for receptor binding, thereby blocking the action of testosterone and also the production of testosterone by the testes.  Other non-steroidal anti-androgens inhibit the conversion of DHT from testosterone.  Some drugs have anti-androgenic activity as a side effect. 

Products for blocking the action of androgens

• Dutasteride and Finasteride are 5α-reductase inhibitors and work by inhibiting the action of the enzyme type II 5α-reductase, which converts the male hormone testosterone to DHT
• Flutamide is a non-steroidal anti-androgen that blocks the action of androgens by binding to same receptor but has no steroid effects
• Bicalutamide is a non-steroidal anti-androgen
• Cyproterone is a steroidal anti-androgen
• Spironolactone is a synthetic steroid which is primarily a diuretic but has anti-androgenic activity as a side effect and works by by decreasing androgen production