From the FDA Drug Label
The median circulating level of testosterone increased by approximately 10 to 20% but remained within the physiologic range In a separate study in healthy men treated with finasteride 1 mg per day (n=82) or placebo (n=69), mean circulating levels of testosterone and estradiol were increased by approximately 15% as compared to baseline, but these remained within the physiologic range
Finasteride does not cause lower testosterone levels, in fact, it increases testosterone levels by approximately 10 to 20% in some cases, but these levels remain within the physiologic range 1.
- The increase in testosterone levels is due to the inhibition of 5α-reductase, which converts testosterone to DHT.
- The levels of testosterone remain within the normal range, even with long-term treatment.
From the Research
Finasteride, a 5-alpha-reductase inhibitor, does not typically cause hypogonadism or low testosterone levels, and in fact, can lead to a slight increase in total testosterone levels in some men. This is because finasteride works by blocking the conversion of testosterone to dihydrotestosterone (DHT) by inhibiting the 5-alpha-reductase enzyme, but it does not directly reduce testosterone production 2. The medication is commonly prescribed at 1mg daily for male pattern hair loss and 5mg daily for benign prostatic hyperplasia. Some men taking finasteride may experience sexual side effects such as decreased libido, erectile dysfunction, or ejaculatory disorders, which can sometimes be confused with symptoms of hypogonadism, but these effects are not due to lowered testosterone levels 2. Rather, they may be related to the reduction in DHT or other mechanisms.
Key points to consider:
- Finasteride inhibits the conversion of testosterone to DHT, but does not affect testosterone production directly 3, 4
- Some studies have shown that finasteride can lead to a slight increase in total testosterone levels in some men 2
- Finasteride is commonly prescribed for male pattern hair loss and benign prostatic hyperplasia, and its effects on testosterone levels are well-studied 5, 6
- Sexual side effects experienced by some men taking finasteride are not due to lowered testosterone levels, but may be related to the reduction in DHT or other mechanisms 2
In terms of morbidity, mortality, and quality of life, the use of finasteride is generally considered safe and effective, with minimal impact on testosterone levels. However, as with any medication, patients should be monitored for potential side effects and their healthcare provider should be consulted if they experience any concerning symptoms. Overall, the evidence suggests that finasteride does not typically cause hypogonadism or low testosterone levels, and its use is not expected to have a significant impact on morbidity, mortality, or quality of life in terms of testosterone-related effects 3, 4, 2, 5, 6.