Flutamide is a nonsteroidal antiandrogen medication that is primarily used to treat prostate cancer in men. It works by blocking the effects of testosterone in the body. Flutamide prevents testosterone from binding to androgen receptors, which stops testosterone from stimulating prostate cancer cell growth.
While a common misconception is that flutamide increases testosterone levels, this is not the case. Flutamide does not actually increase the production of testosterone in the testes or adrenal glands. However, it can cause a temporary increase in serum total testosterone levels.
Here's a more detailed explanation of what happens:
When flutamide blocks testosterone receptors, it causes a feedback loop that tells the pituitary gland to release more luteinizing hormone (LH). LH then signals the testes to produce more testosterone. This results in slightly elevated total testosterone levels in the blood.
However, the newly produced testosterone is unable to bind to receptors and is essentially inactive. So while serum testosterone goes up, the amount of testosterone that can actually act on tissues goes down.
In other words, the total testosterone level increase caused by flutamide is misleading, since most of that testosterone is biologically inactive. The drug is still successfully blocking testosterone's effects.
Some key points:
- Flutamide does not directly increase testosterone production. The testosterone increase is an indirect, secondary effect due to disruption of the negative feedback loop.
- The elevated total testosterone has reduced biological activity due to receptor blockade by flutamide.
- Clinically, flutamide acts to reduce androgen effects in the body. So despite increases in serum testosterone, it ultimately lowers testosterone activity at the tissue level.
- The testosterone boost is temporary. Over time, the HPG axis adjusts to the drug effects and total testosterone returns to normal.
- Monitoring free or bioavailable testosterone (the active fractions) gives a more accurate picture than total testosterone when on flutamide.
- Dosage and individual factors may modulate the degree of testosterone increase seen. Higher doses and more advanced prostate cancer tend to lessen the effect.
So in summary, while flutamide can increase total serum testosterone, this outcome is multifaceted and not clinically indicative of true androgenic status. The elevated total testosterone levels do not overcome the antiandrogenic effects of flutamide. Clinicians should assess clinical response and free/bioavailable testosterone rather than relying solely on total testosterone when monitoring patients on flutamide.
Harmony Hormone Clinic offers comprehensive care for men with prostate cancer or other conditions requiring testosterone suppression. Our clinicians have extensive experience using flutamide and work closely with patients to provide ongoing monitoring, lifestyle counseling and emotional support during treatment. We offer cutting-edge hormone testing and are leaders in providing nuanced, individualized clinical management focused on optimizing quality of life. Contact us today to learn more about evidence-based approaches for prostate cancer,
hypogonadism, transgender care and other hormonal conditions.
