MOST NIPPLE CONVERSATIONS center on women. Think: breastfeeding or nipple slips. On the other hand, men’s nipples tend to be an afterthought, with some questioning why they even have them.
So why do men have nipples?
The reason has to do with embryology, or the study of development in the womb, says Stephen Kappa, M.D., a urologist and men’s sexual health expert at The Urology Group in Fairfield, Ohio.
“The simple answer is that it comes standard with the model,” says Jeffrey Laitman, Ph.D., a professor at the Icahn School of Medicine at Mount Sinai. “Ebryologically, before birth, in what we call the embryo in the fetal period, that is when the neutral breast tissue and neutral nipple area is laid down.”
In other words, before gender is determined in the womb, the embryo develops breasts and then nipples, Dr. Laitman says, and they usually stay for life. (There are some exceptions, however: If someone suffers from athelia, a rare condition where an embryo doesn’t develop one or both of their nipples, he says.)
During puberty, girls’ breast tissue starts to develop, while boys’ typically doesn’t. But their nipples remain. However, men’s nipples don’t function the same as women’s.
That doesn’t necessarily mean they’re function-less, doctors say. Here’s what you should know about men’s nipples and the purpose they serve.
Why do men have nipples?
In the womb, males and females both inherit copies of genes—from their mother and father, Dr. Kappa explains. “Early in development, males and females have the same genetic blueprint.”
Nipples develop early in the womb before the sixth week of pregnancy, which is when sexual differentiation begins, he says. That’s driven by the Y chromosome, which distinguishes a fetus as male.
“That’s where you get testicular development and a variety of other differentiating characteristics between men and women,” Dr. Kappa says. “Nipples just develop very early on.”
The functional differences between a woman’s and a man’s nipples don’t begin until puberty, when “individuals grow postnatally and hormones start to come into play,” Dr. Laitman says.
In puberty, girls’ breast tissue starts to develop for lactation. Men’s nipples…just stay there. However, some men can develop breast tissue during puberty or later, a condition known as gynecomastia, where male breast tissue is overdeveloped.
Do men’s nipples serve a purpose?
Men’s nipples are often viewed as vestigial, meaning a body part that develops but doesn’t have a function, such as your appendix. Men don’t breastfeed, after all. But Dr. Kappa says nipples do have a function.
Men have the same glands, nerves, and surrounding tissues that women do, Dr. Laitman says. In women, the glands help lubricate the area and make it softer for breastfeeding. In men, they help make nipples sensitive in a good way during sex.
Research shows that men have a dense supply of nervous tissue in their nipples and that nipple stimulation fires up areas of the brain in a similar way as genital arousal. About 50 percent of men report that nipple stimulation caused or enhanced their sexual arousal, other research shows.
“There is not the same functional purpose that women have, but there’s certainly, potentially a sexual purpose for them,” Dr. Kappa says.
Erogenous zones are very important, Dr. Laitman adds. “The nipple is not a useless structure in men. It has been retained for those purposes.”
Can men lactate?
Male nipples can occasionally have discharge. But that doesn’t necessarily mean men can breastfeed. Men have the same breast functions—lactiferous ducts and milk-producing areas—as women, albeit on a smaller, underdeveloped scale, Dr. Laitman says.
Men can leak discharge from their nipples for a few reasons, including a condition called galactorrhea. This can be caused by factors such as medication side effects and disorders of the pituitary gland.
Some medications, including antipsychotic, antidepressant, and hypertension drugs, could also trigger nipple secretion, Dr. Kappa says. However, it’s not common.
Signs You Should See a Doctor About Your Nipples
Though not exactly nipple-related, there are some conditions that could affect men’s breast tissue.
For instance, gynecomastia can be caused by low testosterone levels, pituitary gland tumors, thyroid disease, or kidney disease, Dr. Kappa says. Men can also develop breast cancer, though it’s rare.
If you notice pain, discharge, bleeding, or discomfort in the nipple area, see your doctor.
“These are symptoms that men shouldn’t ignore,” Dr. Kappa says.
