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Your Good Health: Finasteride linked to rare cases of impotence and cancer

Breast enlargement, a breast mass or pain, or a change in the nipple should prompt a man not only to stop the medicine, but to get a prompt evaluation for rare cases of cancer.
Dr. Keith Roach.

Dear Dr. Roach: Please tell us about the safety of taking 5 mg of finasteride for benign prostatic hyperplasia (BPH). One urologist prescribed it, claiming that it is safe and prevents serious bladder and prostate problems. Another urologist warned that the dosage has dangerous side-effects and to stop taking it.

A friend took it for over one year and developed breast cancer. Another developed large breasts and stopped taking it. His breasts have not returned to normal, and he is impotent. I realize these are only two out of millions of men who are taking finasteride for BPH.

So, please give us your experienced medical opinion. I’m 83 years old and have had a large prostate for years that has caused me urination problems.


Finasteride works by blocking the formation of a hormone called dihydrotestosterone, which causes enlargement of the prostate and promotes hair loss. Finasteride is used in men with an enlarged prostate and in both men and women for hair loss.

There was concern about the risk of prostate cancer with finasteride, but the data strongly show that finasteride reduces the risk of prostate cancer. Breast enlargement with finasteride happens in 1% to 2% of men, but the risk of male breast cancer is harder to be sure of because male breast cancer is an uncommon disease, about one man out of 100,000 each year.

There have been less than 100 reported cases of male breast cancer associated with finasteride use worldwide. A study from Denmark and Finland suggested that men might be at higher risk; however, that risk was very small — 0.003% of men, or about one in 30,000, taking finasteride who got breast cancer and wouldn’t be expected to get breast cancer if they weren’t taking the medicine. Other studies showed no increase in risk. Sexual function is reduced in about 2% of men taking finasteride.

Given these results, I say that finasteride is still pretty safe. Men who develop sexual side-effects should stop taking it. Sexual function should return after stopping the medicine. Breast enlargement, a breast mass or pain, or a change in the nipple should prompt a man not only to stop the medicine, but to get a prompt evaluation to look for the rare case of breast cancer.

Dear Dr. Roach: I read your recent column regarding iron deficiency in COVID patients. The column compared chelated iron supplements with regular iron supplements that cause upset stomach or constipation.

I take a slow-release iron tablet, and that prevents the constipation. I was a little surprised that you had not mentioned it. It requires a little more expense, but it really works without getting an upset stomach or constipation.


Some people do well with slow-release iron preparations, although there is not good data to suggest that they have fewer side-effects overall.

The concern that I have is that, for at least some preparations in some people, the tablets are excreted whole, having never been absorbed at all! This obviously doesn’t lead to an upset stomach or constipation, but it doesn’t help iron deficiency. Furthermore, iron is best absorbed in the early part of the small intestine. Slow-release tablets don’t allow the iron to be available in the part of the intestine where iron is best absorbed.

Email questions to [email protected].