Male lactation

Template:Short description Template:Use dmy dates

Production of milk (lactation) from a male mammal's mammary glands is well-documented in the dayak fruit bat and the Bismarck masked flying fox. The term "male lactation" is not used in human medicine. It has been used in popular literature, such as Louise Erdrich's The Antelope Wife, to describe the phenomenon of male galactorrhea, which is a human condition unrelated to childbirth or nursing. Newborn babies of both sexes can occasionally produce milk. This is called neonatal milk (also as "witch's milk") and not considered male lactation.

HistoryEdit

Male lactation was of some interest to Alexander von Humboldt, who reports in Voyage aux régions équinoxiales du Nouveau Continent about a citizen of the Venezuelan village of Arenas (close to Cumana) who allegedly nurtured his son for three months when his wife was ill,<ref> Voyage de Humboldt et Bonpland; 1-3. Voyage aux régions équinoxiales du Nouveau Continent : fait en 1799, 1800, 1801, 1803 et 1804. Tome 1 / par Al. de Humboldt et A. Bonpland; rédigé par Al. de Humboldt; J. Smith (Paris), 1814-1825, p. 376, (Online at gallica)</ref> as well as Charles Darwin, who commented on it in The Descent of Man, and Selection in Relation to Sex (1871):

It is well known that in the males of all mammals, including man, rudimentary mammae exist. These in several instances have become well developed, and have yielded a copious supply of milk. Their essential identity in the two sexes is likewise shown by their occasional sympathetic enlargement in both during an attack of the measles.<ref>Descent of Man, Chapter I</ref>{{#if:|{{#if:|}}
— {{#if:|, in }}Template:Comma separated entries
}}

{{#invoke:Check for unknown parameters|check|unknown=Template:Main other|preview=Page using Template:Blockquote with unknown parameter "_VALUE_"|ignoreblank=y| 1 | 2 | 3 | 4 | 5 | author | by | char | character | cite | class | content | multiline | personquoted | publication | quote | quotesource | quotetext | sign | source | style | text | title | ts }}

Darwin later considered the nearly perfect function of male nipples in contrast to greatly reduced structures such as the vesicula prostatica, speculating that both sexes may have nursed young in early mammalian ancestors, and subsequently mammals evolved to inactivate them in males at an early age.<ref>Descent of Man, Chapter VI</ref>

Evolution and biologyEdit

Male mammals of many species have been observed to lactate under unusual or pathogenic conditions, such as extreme stress, castration, and exposure to phytoestrogens, or pituitary tumors. Therefore, it is hypothesized that while most male mammals could easily develop the ability to lactate, there is no selective advantage to male lactation. While male mammals could, in theory, improve their offspring's survival rate through the additional nourishment provided by lactation, most have developed other strategies to increase the number of surviving offspring, such as mating with additional partners. Presently, very few species are known where male lactation occurs and it is not well understood what evolutionary factors control the development of this trait.<ref name=Kunz_2009>Template:Cite journal</ref>

Nonhuman animal male lactationEdit

The phenomenon of male lactation occurs in some species, notably the dayak fruit bat (Dyacopterus spadiceus), lesser short-nosed fruit bat (Cynopterus brachyotis), and the Bismarck masked flying fox (Pteropus capistratus). Lactating males may assist in the nursing of their infants. In addition, male goats are known to lactate on occasion.<ref>Template:Cite journal</ref>

Human male lactationEdit

Spontaneous production of milk not associated with childbirth, known as galactorrhea, can occur in human males and females.<ref name=Rohn_1984>Template:Cite journal</ref> Case reports of lactation induced in transgender women have been published.<ref name=Reisman_2018>Template:Cite journal</ref><ref name=Wamboldt2021>Template:Cite journal</ref>

ReferencesEdit

CitationsEdit

Template:Reflist

SourcesEdit

Template:Refbegin

Template:Cite news Template:Open access
Cr. J. Covey, Francis, Charles M., et al.; "Lactation in Male Fruit Bats," Nature, 367:691, 1994.
Fackelmann, K.A.; Science News, 145:148, 1994.
Anomalies and Curiosities of Medicine G.M. Gould and W.L. Pyles

Template:Refend