We all know why women have nipples - to feed babies, right? Although with the whole 'breastfeeding in public' debate, you'd think they were strictly for porn and sex and nothing else.
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Anyway, you may have wondered why men have nipples. They serve no purpose, right? Well, you may or may not know that everyone starts off as a female embryo in the womb. So the nips grow for the first several weeks. For men, testosterone then kicks in and changes the genetic activity in your genitals and brain.
HOWEVER - here's something I didn't know - men can actually lactate in certain circumstances. So they're not completely decorative.
A 2008 review on male lactation published in the journal, Trends in Ecology and Evolution, documented male lactation in male WWII prison camp survivors. These men had survived months of starvation. Once they were given food and water, their hormone-producing glands rebounded far quicker than their livers (these normally metabolize hormones). This resulted in hormonal spikes that caused lactation.
The same review also noted that a condition called liver cirrhosis can also cause lactation. This is because it disrupts the liver's hormone-metabolizing function.
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Health issues that affect the pituitary gland or the hypothalamus (which normally inhibits the release of prolactin) can also lead to male milk production.
So there you go. Learn something new every day.
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