Using finasteride for hair loss is like shooting at sparrows with cannons. The drug.…blocks not only the super hormone but also other hormones that affect thinking and psyche, mood and emotions. Discontinuation of the drug should actually make the hormones work again.…but apparently, something breaks down in some men, in the prostate, in the brain, in the whole organism.

—I Didn’t Want to Go Bald. A Pill the Doctor Gave Me Destroyed My Life (English translation): Die Zeit, Feb. 22, 2018

We are certainly very cautious, because we see the side effects. We wouldn’t recommend that any man take [finasteride], especially not young men. The longer they take it, the greater the risk of experiencing persistent side effects, including after they’ve stopped.

—Do Anti-Baldness Remedies Make You Impotent? Puls, SRF-TV, May 7, 2018

[W]e have evaluated in male rats the effects of a subchronic treatment with low doses of finasteride.…and the consequences of its withdrawal.…on neuroactive steroid levels…. Interestingly, at the withdrawal, some of these effects persisted, and different changes in neuroactive steroid levels, and in the expression of receptors, were also detected. Altogether these findings suggest that the block of the enzyme 5alpha-reductase by finasteride treatment may have broad consequences for the nervous system.

—Effect of Finasteride, an Inhibitor of the Enzyme 5alpha-Reductase, in the Nervous System: The Journal of Steroid Biochemistry and Molecular Biology, July 2017

“Finasteride inhibits Type II 5(alpha)-reductase, which metabolizes testosterone to the potent androgen 5(alpha)-dihydrotestosterone. FDA is concerned that use of finasteride by pediatric patients may pose long-term safety risks regarding growth, development and sexual function.”

—FDA response to Merck & Co.’s citizen petition requesting that finasteride be added to the List of Approved Drugs for Which Additional Pediatric Information May Produce Health Benefits in the Pediatric Population: May 2000