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Menopause

Human Anatomy, Physiology, and Medicine. Anything human!

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Postby kotoreru » Sun Aug 19, 2007 11:27 am

I've never heard of the male menopause. If it does exist then it is certainly far less obvious than the female equivalent.

Just off the top of my head though: female menopause would happen earlier because they are born with a limited number of egg cells, men have no such limit.

Presumably if it did exist then male menopause would occur not because of the sperm numbers running out, but because of the 'machinery' that churns them out ceasing to work.
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Postby Darby » Mon Aug 20, 2007 2:03 am

Females don't run out of egg cells - menopause, like many things, is genetically timed. Some older references will give the egg cell explanation, though.

Male menopause doesn't seem to be a real reproductive effect - often it is discussed in relation to some of the psychological and physiological side-effects of female menopause.
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Postby MrMistery » Mon Aug 20, 2007 11:05 am

A female is born with a limited number of eggs. However, they are somewhere in the milions. Out of this huge number of egg cells, only about 400 will reach the stage of secondary ovocyte over the years. The process is indeed, genetically timed.

Actually in 2004 some researchers found out that mouse egg cells can in fact divide. I didn't follow up on the experiments in that direction, but it is a real possibility that this also occurs in humans, since human physiology is not that different from that of a mouse.

One more thing. Human menopause is an evolutionary mystery. It would make more sense that if a female produces more offspring her fitness increases; therefore it would seem like an evolutionary advantage to be able to produce fertile eggs for as long as possible. The chief hypothesis why this does not happen is that by running out of eggs, a female can care for the offspring she already has, thus increasing their survival rate and her fitness. But this just a hypothesis.
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Postby Annij » Sun Nov 03, 2013 5:22 am

It is now understood that mammals are NOT born with all the eggs they will ever have, but do produce them over the course of their reproductive life. Human women are exceptionally rare in the mammalian world in that they can undergo fertility cessation, at so very young an age (37), when women are living to 92 in places like Japan. There are lots of theories as to when and why menopause began, but it is an anomalous genetic mutation as evolution favours reproduction, not cell death. Scientists are trying to cure menopause (like trying to cure Alzheimer) as it is very dangerous on the female body. Even if women choose not to have anymore children past the age of 30, it is very important that menopause be eradicated.
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Postby Annij » Sun Nov 03, 2013 5:23 am

It is now understood that mammals are NOT born with all the eggs they will ever have, but do produce them over the course of their reproductive life. Human women are exceptionally rare in the mammalian world in that they can undergo fertility cessation, at so very young an age (37), when women are living to 92 in places like Japan. There are lots of theories as to when and why menopause began, but it is an anomalous genetic mutation as evolution favours reproduction, not cell death. Scientists are trying to cure menopause (like trying to cure Alzheimer) as it is very dangerous on the female body. Even if women choose not to have anymore children past the age of 30, it is very important that menopause be eradicated.
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Postby Darby » Sun Nov 03, 2013 2:59 pm

This is a long way from being settled. The first suggestive test involved moving bone marrow stem cells to ovaries and getting follicle and oocyte cells - instead of deciding that stem cells could generate new tissue to match their environment, the researchers decided that back-up follicle cells were stored in marrow (!). Certainly not the likeliest possibility. Newer research indicates that, although new cells might be generated with laboratory "pokes," such generation may not be happening under natural conditions.

If new generation happens, it certainly isn't at significant levels, or it probably would have been noted before.
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