What is Finasteride?
Finasteride is a prescription drug available as an oral tablet. It is marketed under Proscar and Propecia and is also available in generic form. It is a selective type II 5α-reductase inhibitor, an inhibitor of the enzyme that converts testosterone to dihydrotestosterone (DHT) in the targeted tissues, including the prostate and hair follicles [1, 2, 3].
What does Finasteride do?
Finasteride works mostly by lowering the amount of DHT in your body, which is a hormone that can lead to your prostate getting larger and could result in balding on your head. This decrease in DHT interferes with the prostate’s ability to expand and would result in side effects of increased hair growth and decreased hair loss in your head. Hair growth elsewhere on your body is unaffected [3].
The drug, marketed in different formulations for treating different conditions, acts on symptoms of an enlarged prostate (benign prostate hyperplasia) and as an adjunct to other medications to reduce the risk of progression of symptoms of an enlarged prostate. However, Finasteride is not meant to cure enlarged prostate nor be used in women or in children [3].
Over six months, patients with benign prostatic hyperplasia (BPH) saw a mean shrinkage in prostate volume of 28% after taking finasteride without clinical adverse effects [4]. When it comes to hair loss, these exposures can produce measurable hair growth in up to two-thirds of men with mild to moderate alopecia, and in 91% of patients, the substance stops hair loss [5].
Benefits of Finasteride
Finasteride, however, has several advantages, especially for men. Most notably, research has shown that finasteride is a safe and effective way to treat androgenetic alopecia—what doctors call male-pattern baldness. In clinical trials, 66% of men with mild to moderate alopecia reported that finasteride was effective at regenerating hair, and 91% stopped hair loss [5].
The other, equally important, is that finasteride becomes beneficial in a condition known as benign prostatic hyperplasia, which begins with an enlarged prostate gland. In this condition, finasteride leads to major benefits in men with BPH, with robust and sustained decreases in prostatic volume and the level of prostate-specific antigen (PSA) at minimal cost of side effects [6, 7].
Other large-scale studies have also shown that finasteride lowers the risk of prostate cancer. Some studies indicate that taking finasteride reduces the risk of all types of prostate cancer by 30%, and the risk of clinically significant prostate cancer, including high-grade cancers, is reduced by almost 50% [8].
Although it isn’t FDA-approved, topical finasteride doesn’t have some systemic side effects of orally administered finasteride but has been demonstrated to be as effective as the oral form [9].
Finally, recent work has suggested that finasteride attenuates the development of cardiovascular disease via an improvement in plasma lipid profile [10].
Side Effects of Finasteride
Finasteride can have several side effects, including common and less-common but more serious side effects.
Among the most common adverse effects are low sex drive, inability to get or maintain an erection, and problems in ejaculation [11, 12, 3]; some men will also experience enlargement of the breasts and tenderness of the nipples [12, 3]. Finasteride can induce rashes of the skin [11, 3].
Serious but uncommon side effects include oedema of the lips, tongue, throat and face and depression [11, 12, 3]. Some men will experience lumps or pain in the breasts and nipple titillation [3]. High−grade prostate cancers result from the reduction in levels of serum prostate-specific antigen (PSA) [11], while male breast cancer has been reported in extremely rare cases.
This is not to say that some men do not have persistent side effects after stopping the medication. Post-finasteride syndrome, defined as persisting sexual side effects (such as erectile dysfunction and low libido) and symptoms of depression and anxiety, has been reported after discontinuation of finasteride. However, it is rare [12, 13].
Please consult your doctor before beginning any treatment, especially if you have a medical condition, and seek immediate medical attention if you experience severe side effects or if they last for a long time [11, 3].
Does Finasteride Promote Muscle Growth?
The specific effect of finasteride on muscle-building is complex, and due to the limited availability of studies, it is hard to determine whether there is a cause-and-effect relationship.
One study in older hypogonadal men brought the benefits of testosterone enanthate (TE), a form of testosterone, into focus. Over a year, combining T and finasteride significantly increased muscle strength and bone mineral density (BMD) and decreased body fat. Muscle strength in the upper and lower body increased by 8-14%, the fat-free mass increased by 4.04 kg, and total body fat decreased by 3.87 kg. However, its co-administration with finasteride did not diminish these effects [14].
Conclusion
Overall, while finasteride may not be a muscle-building agent per se, it doesn’t appear to negate the muscle-building effects of testosterone supplementation. Larger studies of the impact of finasteride on muscle growth are needed in younger and more athletically inclined people. More evidence will provide clearer answers.