Steroidal antiandrogens

Steroidal antiandrogens are a class of pharmacological agents that act as antagonists of the androgen receptor (AR) and inhibit the biological effects of androgens like testosterone and dihydrotestosterone (DHT) in the body. They are a subset of antiandrogens, which also includes non-steroidal antiandrogens. Steroidal antiandrogens are primarily used in the treatment of prostate cancer, as well as for other conditions like hirsutism, acne, and in hormone therapy for transgender women.

Mechanism of Action

Steroidal antiandrogens work by directly competing with androgens for binding sites on the androgen receptor, thereby preventing the activation of the receptor by these endogenous hormones. Unlike non-steroidal antiandrogens, which typically block the receptor without activating it, some steroidal antiandrogens can act as partial agonists, meaning they might activate the receptor to a lesser extent than androgens. This partial agonist activity can vary depending on the tissue type, making some steroidal antiandrogens act as antagonists in certain tissues while having agonist effects in others.

Clinical Uses

The primary use of steroidal antiandrogens is in the treatment of prostate cancer. By blocking the action of androgens, these drugs can slow the growth of androgen-dependent prostate cancer cells. Steroidal antiandrogens are also used in the management of other conditions related to androgen excess, including hirsutism and severe acne, particularly when other treatments have failed. In the context of transgender hormone therapy, steroidal antiandrogens may be used to block the masculinizing effects of testosterone, aiding in the feminization process for transgender women.

Examples

Some common steroidal antiandrogens include:

• Cyproterone acetate (CPA) - A potent steroidal antiandrogen that is also a progestin. It is widely used in Europe and Canada but is not available in the United States.
• Spironolactone - Although primarily a potassium-sparing diuretic, spironolactone has antiandrogenic effects and is frequently used off-label for this purpose, especially in the treatment of hirsutism and as part of hormone therapy for transgender women.
• Chlormadinone acetate (CMA) - Similar to CPA, CMA is a steroidal antiandrogen with progestogenic activity.

Side Effects

The use of steroidal antiandrogens can be associated with a range of side effects, largely due to their antiandrogenic and progestogenic activities. Common side effects include gynecomastia, reduced libido, and fatigue. Due to their potential for liver toxicity, monitoring of liver function tests is recommended during treatment. Additionally, because these drugs can cause feminization effects, they are generally not used in cisgender men except for the treatment of prostate cancer.

See Also

• Androgen deprivation therapy
• Non-steroidal antiandrogen
• Prostate cancer
• Transgender hormone therapy