Finasteride, marketed under brand names like Propecia and Proscar, is a widely prescribed medication for two distinct male health concerns. The 1 milligram (mg) dose treats male pattern hair loss (androgenetic alopecia). The higher 5 mg dose manages the symptoms of benign prostatic hyperplasia (BPH), or an enlarged prostate. Since the medication is often taken by men in their reproductive years, concerns frequently arise regarding its potential impact on fertility. This is relevant because the drug’s mechanism involves hormones crucial for sperm production and function.
How Finasteride Affects Hormonal Balance
Finasteride belongs to a class of drugs called 5-alpha reductase inhibitors, blocking the action of the Type II 5-alpha reductase enzyme. This enzyme converts the androgen testosterone into the more potent hormone dihydrotestosterone (DHT). By inhibiting this conversion, finasteride significantly lowers the concentration of DHT in the body, including in reproductive tissues. Research shows finasteride can reduce serum DHT levels by approximately 70% and prostate DHT levels by up to 90%. This reduction provides the therapeutic effect for both hair loss and BPH, as DHT is the primary hormone responsible for shrinking hair follicles and stimulating prostate growth. DHT is also a factor in the development and maintenance of male reproductive organs, including the prostate and seminal vesicles. These glands produce the fluid that makes up semen, meaning the lowering of DHT levels can affect their function and the overall composition of the ejaculate.
Documented Effects on Semen Parameters
Clinical data regarding finasteride’s effect on semen parameters show varying degrees of impact depending on the dosage and the individual’s pre-existing fertility status. Studies involving the 5 mg dose, typically used for BPH, have consistently documented changes in semen quality. This higher dose has been associated with a reduction in ejaculate volume, sometimes by as much as 25%. It may also result in decreased sperm concentration (oligospermia) and reduced sperm motility.
The effect of the 1 mg dose, commonly used for hair loss, appears to be less pronounced in men with normal fertility. One double-blind, placebo-controlled study of young men taking 1 mg finasteride daily for nearly a year found no significant effects on overall sperm concentration, motility, or morphology. Despite this, a small decrease in ejaculate volume, around 11%, was noted in the finasteride group.
For men with pre-existing subfertility, even the lower 1 mg dose may have a more substantial effect on semen parameters. In men presenting to fertility clinics who were taking finasteride, a small percentage exhibited severe oligospermia or azoospermia (the complete absence of sperm). These findings suggest that while finasteride does not cause clinically significant fertility issues in the majority of men, it may exacerbate or reveal underlying sperm production problems in a sensitive subset of the population.
Reversibility and Clinical Guidance
The evidence strongly indicates that any adverse changes to semen parameters caused by finasteride are temporary and reversible upon stopping the medication. Finasteride does not cause permanent male infertility. For most men who experience a decline in semen quality, sperm parameters often return to pre-treatment levels within several weeks to a few months after discontinuation.
In cases where men with severe oligospermia stopped taking finasteride, significant improvements in sperm count were observed, with some men seeing an average increase of over tenfold. This recovery highlights the temporary nature of the drug’s effect on the reproductive system.
For patients actively trying to conceive or those experiencing fertility challenges while on the medication, healthcare providers may recommend discontinuing finasteride for a period. The typical recommendation is to stop the drug and allow the reproductive system to recover, with semen analysis often showing improvement within three to six months. Consulting with a urologist or a fertility specialist is advisable for men with pre-existing fertility concerns before starting finasteride. A specialist can perform a baseline semen analysis and provide personalized guidance on pausing treatment to optimize conception chances.