There’s a great scene in Meet the Parents in which Ben Stiller’s character Greg is trying to convince his future father-in-law, played by Robert DeNiro, of his history of milking cats in Detroit. He claims it’s possible because cats have nipples. DeNiro’s character replies, “I have nipples, Greg. Can you milk me?”

In spite of the disturbing mental image this conjures, it actually is possible for men to produce breast milk. As DeNiro’s character so comedically noted, men do indeed have nipples. They also have the rudimentary breast tissue and ductal structure that would make the production of milk, called lactation, possible. What they lack is the proper combination of hormones to plump up the breast tissue and stimulate the production of milk.

The formation and proliferation of breast tissue is dependent on the hormone estrogen. Though generally considered to be a “female” hormone, men do produce small amounts of estrogen, as well. In men, its effects are usually tempered by the large amount of testosterone that they produce. The actual production of milk by the breast tissue is dependent on the hormone prolactin, which is secreted by the pituitary gland in the brain. Following the birth of a child, the pituitary gland increases its secretion of prolactin, enabling the new mother to begin producing milk for her infant. Stimulation of the nipples by the nursing infant also causes a spike in prolactin production.

Most cases of male breast formation and lactation in humans are the result of disease or medication side effects and not the need to feed their offspring. The medical literature is replete with reports of men developing breast tissue due to medications or medical conditions. Fat cells are known to increase the production of estrogen, so it’s not uncommon for obese men to develop more prominent breast tissue, known as gynecomastia. In addition, steroid use, cirrhosis, certain medications and certain herbal formulations may cause gynecomastia. Reports of males producing milk are much less common, and are usually seen in infancy when the baby’s overall hormonal status is in quite a bit of flux. And although multiple causes of increased prolactin secretion exist, such as from a pituitary tumor or side effect of a medication, men rarely get galactorrhea as a result.

So while male lactation is possible, it’s very rare, and almost never physiologic. And for those of you who are fans of Meet the Parents, please don’t try this at home.

References

Devidayal (2005). A Male Infant with Gynecomastia-Galactorrhea The Journal of Pediatrics, 147 (5), 712-712 DOI: 10.1016/j.jpeds.2005.06.026

van der Steen M, Du Caju MV, Van Acker KJ. Gynecomastia in a male infant given domperidone. Lancet. 1982 Oct 16;2(8303):884-5.