Lose your hair or lose your libido. That’s a decision you might have to make if you’re guy going bald. Talk about being caught between a bald rock and a hard place. Propecia® (generic name is finasteride) can cause low libido and/or erectile dysfunction in some men, which is bad enough. What’s worse is that there is now evidence that these symptoms can persist for at least 3 months or longer after discontinuation of Propecia® based on this study published in the Journal of Sexual Medicine. The mean duration of sexual symptoms following discontinuation of finasteride was 40 months in that study. That’s quite a while to be suffering from sexual dysfunction.
How Propecia® Works
Testosterone gets converted to dihydrotestosterone, or DHT by the enzyme 5α-reductase. The concentration of 5α-reductase is high in the prostate, skin, and scalp. DHT is 3 to 10 times more potent than testosterone. Both testosterone and DHT are important for libido, but since DHT is more potent it is the more important hormone of the two. Excessive DHT levels are associated with male-pattern baldness.
Propecia® is real effective in lowering DHT levels in the scalp, but a major drawback is men can develop low libido and erectile dysfunction if DHT levels are dropped too much. Measuring DHT levels is essential if a male is taking Propecia®. Though the typical dose is 1 mg a day we have found that frequently DHT levels can be lowered into a safe range with sometimes as little as 1 mg 2 or 3 times a week, yet be effective enough to slow or stop hair loss. The smallest doses of finasteride and other 5α-reductase drugs like duasteride (Avodart®) should be used to lower DHT levels to prevent unwanted side effects.
Other Side Effects of 5α-Reductase Inhibitors
Low libido isn’t the only side effect of 5α-reductase inhibitors. Other side effects include decrease ejaculatory volume, abnormal ejaculation, breast development (gynecomastia), and testicular pain. It was once thought that many of these side effects only occurred in a small number of patients and resolved shortly after discontinuation of the drugs, but the study in the Journal of Sexual Medicine suggests otherwise.
In that study 94% of the men developed low libido, 92% developed erectile dysfunction, 92% decreased sexual arousal, and 69% developed orgasmic difficulty. These percentages are much higher than what we have seen in our patients and most likely is related differences in doses of finasteride used in the study and what we typically use in our practices.
These findings of sexual symptoms following use of finasteride to treat male-pattern baldness highlight the importance of close physician supervision and the monitoring of DHT levels (and other hormone levels) in men taking finasteride.
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