Soon after Will Stone and his wife, Brittany, got married in 2021, they started trying to have a baby. But early attempts didn’t pan out, and by the next year, they went in for testing.
Ms. Stone’s results came back normal. But Mr. Stone’s were more disappointing.
His sperm count was about 2 million per milliliter, far below the 10-million threshold his doctor told him was optimal for the couple to try intrauterine insemination, or I.U.I. He was referred to a urologist, who asked what medications he was taking.
When Mr. Stone, a data analyst in Austin, Texas, mentioned he took a 1 milligram dose of finasteride, a daily pill for hair loss, the urologist interrupted him.
“He told me to stop taking it immediately,” Mr. Stone, now 32, said.
Finasteride, sometimes sold as Propecia, is the most widely used prescription medicine for male-pattern baldness. Prescriptions have reportedly tripled in recent years alongside the rise of direct-to-consumer telehealth companies popular among young men.
For many, the medication comes with no issues and can provide newfound confidence, but it does carry side effects. Mr. Stone had known there was a small possibility of reduced libido and erectile dysfunction (between 1 and 2 percent), but he didn’t know that the drug might be linked to his fertility struggles.
Finasteride is prescribed at higher doses to treat enlarged prostates and has been known to mildly affect sperm counts. But Dr. James Kashanian, a urologist and the director of male sexual health at Weill Cornell Medicine, said the drug has also “significantly affected” some patients’ sperm quality, even at 1 milligram, the dose typically prescribed for hair loss.
Unlike with other side effects of the drug, it’s not clear how common reduced sperm counts are, and much of the data is anecdotal. While some doctors say that it can be a significant problem, especially among men already struggling with fertility issues, others say it plays a relatively small role.
Still, many young men are not aware of any potential risks, said Dr. Mary Samplaski, a urologist and the former director of male infertility at the Keck School of Medicine at the University of Southern California.
Mr. Stone had been prescribed finasteride for hair loss through the telehealth company Hims & Hers. A senior vice president at the company said it provides information about finasteride, including a warning on its website about infertility and poor sperm quality.
In most cases, fertility issues seem to reverse within a few months of going off the medication and there is no evidence it causes birth defects. In Mr. Stone’s case, he stopped taking it the day his urologist told him to. When he tested again 10 weeks later, his sperm count had jumped to 250 million per milliliter, a 125-fold increase.
A ‘Male Contraceptive’?
In 1999, the first peer-reviewed study to look at finasteride and sperm quantity found no effects. But a small 2013 study, led by Dr. Samplaski, focused specifically on 27 men dealing with infertility issues while taking finasteride. Researchers asked them to go off the drug for three months, the amount of time it typically takes for a new population of sperm to form. When the men were retested after going off finasteride, they registered an 11-fold increase in sperm counts on average.
Researchers suspect that the reason for the decline in sperm count is that the medication can shift the balance of hormones in the body, said Dr. Scott Lundy, the program director of urology at the Cleveland Clinic. It does this by suppressing the conversion of testosterone to dihydrotestosterone, or DHT, which has been found to lead to baldness.
For some people, disrupting hormonal ratios can create fertility issues. “A lot of people don’t know that testosterone is a male contraceptive,” said Dr. Kirk Lo, a urologist at Mount Sinai Hospital in Toronto who worked on the study with Dr. Samplaski.
However, there are very few high quality studies looking at finasteride and sperm counts, and not every doctor considers it an important factor in fertility. Dr. Kian Asanad, the director of the USC Fertility and Men’s Sexual Health Center, said he couldn’t recall a case when taking a patient off finasteride solved their fertility issues independently.
“I keep it in the back of my mind as a possible factor, but I would say it’s a less common thing,” he said.
In the U.S., Dr. Kashanian said he has had more conversations about finasteride in recent years as more men have come in seeking treatment for infertility.
Dr. Goldstein agreed and said after he lays out the risks of taking finasteride while trying to conceive, some patients will choose to stay on the medication. “Vanity reigns supreme,” he said.
But others, like Mr. Stone are happy to go off. After his sperm count rebounded, last year he and his wife had a healthy baby boy. He has no plans to go back on finasteride any time soon.
“I’d have gladly lost every hair on my head to have the kid we have now,” he said.
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