Men have nipples because of the wayembryosdifferentiate duringgestation(the period between conception and birth). Basically, all embryos come from the same genetic blueprint and, when they begin to differentiate into males and females during the initial weeks, they already have nipples.
Under the influence of the sex hormonetestosterone, the male fetus will start to develop sex organs like thepenisandtesticles, while their nipples and surroundingareolaswill generally end up smaller than those of females.
And, while male nipples have few physiological functions, this shouldn’t suggest that have no function or “don’t do anything.”
This article gets to the point of why men have nipples, including the development and function of nipples as well as various abnormalities that can affect them.
A Note on Gender and Sex TerminologyVerywell Health acknowledges thatsex and gender are related concepts, but they are not the same.Sex refers to biology: chromosomal makeup, hormones, and anatomy. People are most often assigned male or female at birth based on their external anatomy; some people do not fit into that sex binary and are intersex.Gender describes a person’s internal sense of self as a woman, man, nonbinary person, or another gender, and the associated social and cultural ideas about roles, behaviors, expressions, and characteristics.Research studies sometimes don’t use the terminology in this way. Terms that describe gender (“woman,” “man”) may be used when terms for sex (“female,” “male”) are more appropriate. To reflect our sources accurately, this article uses terms like “female,” “male,” “woman,” and “man” as the sources use them.
A Note on Gender and Sex Terminology
Verywell Health acknowledges thatsex and gender are related concepts, but they are not the same.Sex refers to biology: chromosomal makeup, hormones, and anatomy. People are most often assigned male or female at birth based on their external anatomy; some people do not fit into that sex binary and are intersex.Gender describes a person’s internal sense of self as a woman, man, nonbinary person, or another gender, and the associated social and cultural ideas about roles, behaviors, expressions, and characteristics.Research studies sometimes don’t use the terminology in this way. Terms that describe gender (“woman,” “man”) may be used when terms for sex (“female,” “male”) are more appropriate. To reflect our sources accurately, this article uses terms like “female,” “male,” “woman,” and “man” as the sources use them.
Verywell Health acknowledges thatsex and gender are related concepts, but they are not the same.
Research studies sometimes don’t use the terminology in this way. Terms that describe gender (“woman,” “man”) may be used when terms for sex (“female,” “male”) are more appropriate. To reflect our sources accurately, this article uses terms like “female,” “male,” “woman,” and “man” as the sources use them.
Erik Isakson / Getty Images
Fetal Development
The answer is simpler than you think. During the development of an embryo after fertilization (embryogenesis), females and males both start from the same genetic base.
In the initial weeks, there is no differentiation between the biological sexes, even as the embryonic cells continue to divide and specialize. Nipples are already developing at this time.
It is that Y chromosome that leads to the development of the testes in males.By contrast, female embryos undergo changes in the mammary cells, starting with the development of a pit at the center of each nipple. This pit will gradually form a depression that connects to a lactiferous (milk-producing) duct.
While this happens to some degree in males, it is far less profound and developed.
Function of the Male Nipple
While male nipples are sometimes thought to bevestigial—meaning that they have become functionless in the course of evolution, much like the appendix or wisdom teeth—that is largely untrue. They may be more accurately described as remnants of fetal development. But even this suggests that male nipples serve no real purpose.
The nipple, in fact, contains a dense supply of nerves that function as a major stimulatory organ.As such, it can be considered a secondary sex characteristic in males, along with facial hair and an Adam’s apple.
The stimulatory response in males (and females) appears to be unique to the human species. It could potentially have evolutionary value in that it contributes to the desire to reproduce.
This said, the nerve network in the male nipple is much denser than that in the female nipple, meaning that sensory response tends to be more discreet.
Male Nipple Abnormalities
Some characteristics associated with the female breast and nipple can abnormally occur in the male breast and nipple, too. Some are the result of the dysregulation of hormones, while others may be due to genetics.
Galactorrhea
While males will not produce milk under usual circumstances, the male breast can lactate if under the influence of the hormone prolactin.
The condition, known as malegalactorrhea, is uncommon and may occur as a result of a medication or medical condition that triggers an increase in prolactin, a hormone responsible for milk production.
Several types of medications can cause galactorrhea including antipsychotic, antidepressants, antihypertensives, and opioids
Other causes includemalnutrition, pituitary gland disorders,hypothyroidism(low thyroid function), and frequent nipple stimulation.
Gynecomastia
Gynecomastiais the enlargement of male breasts that commonly occurs in older males as testosterone levels progressively drop with age. In addition to the general swelling of breast tissue, gynecomastia can trigger the enlargement of the nipples and surroundingareolas.
Gynecomastia can also affect boys and younger males. In some cases, particularly in adolescent boys undergoing puberty, the condition is temporary. Other common causes include:
Why Males May Experience Breast Pain and Swelling
Summary
Males have nipples because of the way that embryos develop in the initial weeks after gestation. Those eventually born female and male are the same until sex chromosomes are defined, which doesn’t happen until week six or seven of pregnancy. Nipples begin to develop before that time.
Like the appendix and wisdom teeth, male nipples are widely assumed to be functionless. They don’t supply nourishment to newborn babies, but male nipples contain a dense supply of nerves that function as a major stimulatory organ.
Why Some People Have a Third Nipple
Frequently Asked Questions
Typically, the nipples of both sexes are virtually indistinguishable until puberty, during which time they undergo distinctive changes. Male nipples tend to end up being smaller than female nipples. There is also less variation among male nipples than female nipples.
6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Kashimada K, Koopman P.Sry: The master switch in mammalian sex determination.Development. 2010;137(23):3921-30. doi:10.1242/dev.048983.
Schober JM, Meyer-Bahlburg HF, Dolezal C.Self-ratings of genital anatomy, sexual sensitivity and function in men using the ‘Self-Assessment of Genital Anatomy and Sexual Function, Male’ questionnaire.BJU Int. 2009;103(8):1096-103. doi:10.1111/j.1464-410X.2008.08166.x.
Atluri S, Sarathi V, Goel A, Boppana R, Shivaprasad C.Etiological profile of galactorrhoea.Indian J Endocrinol Metab. 2018;22(4):489-493. doi:10.4103/ijem.IJEM_89_18.
National Breast Cancer Foundation, Inc.Male breast cancer.
Allen K, Wise N, Frangos E, et al.Male urogenital system mapped onto the sensory cortex: Functional magnetic resonance imaging evidence.J Sex Med. 2020;17(4):603-613. doi:10.1016/j.jsxm.2019.12.007.
Javed A, Lteif A.Development of the human breast.Semin Plast Surg.2013;27(1):5-12. doi:10.1055/s-0033-1343989.Luanow E, Kettler M, Slanetz P.Spectrum of disease in the male breast.Am J Roentgenology.2011;196: W247-W259. doi:10.2214/AJR.09.3994.
Javed A, Lteif A.Development of the human breast.Semin Plast Surg.2013;27(1):5-12. doi:10.1055/s-0033-1343989.
Luanow E, Kettler M, Slanetz P.Spectrum of disease in the male breast.Am J Roentgenology.2011;196: W247-W259. doi:10.2214/AJR.09.3994.
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