10-nutrition%20%26%20fertility

10-nutrition%20%26%20fertility - Nutritional infertility...

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Nutritional infertility: the effects of food availability on reproduction.
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Why bother to look at the effects of food availability on reproduction?
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“Of the many environmental factors that can influence a mammal’s reproduction, food availability must be accorded the most important role.” F. H. Bronson, Mammalian reproductive biology. Chicago: University of Chicago Press, 1989, p. 88.
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Name: Venus of Willendorf Hometown: Willendorf, Austria Age: ~30,000 years Occupation: Fertility Goddess Nutrition and fertility in women: People have known for a long time that there is an association between adequate nutrition and fertility.
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Without sufficient calories, women become amenorrheic – they no longer exhibit menstrual cycles and do not ovulate. But it also happens in developed societies where ample supplies of food are available: Eating disorders. Endurance athletes. Athletes who limit their food intake. Ballerinas. Gymnasts. Figure skaters. Military basic training. Distance runners. Nutritional amenorrhea is common in the Third World, where calories may be hard to come by.
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Nutritional infertility can be seen in both sexes, but it is far more common among females than males. Why? Even among biparental species, the female expends far more energy than the male during a complete cycle of reproduction – from mating to weaning the offspring. She has far more to lose from a botched reproductive attempt due to insufficient calories – the loss of the litter/baby, or even her life.
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In and of itself, nutritional infertility is not a pathology. It is a perfectly reasonable adaptation to the prevailing environmental conditions. It allows the female to avoid wasting time and energy on a futile, and possibly dangerous, activity. It is completely reversible. There is no harm whatsoever to the reproductive system. So what’s the fuss about nutritional amenorrhea? Osteoporosis and metabolic disorders.
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but when calories are in short supply, animals are forced to set priorities. Reproduction and fat storage have a very low priority Some processes can’t be compromised Others can be reduced When food is abundant, animals can maintain all physiological processes at optimal levels,
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In hamsters, as in other species, both ovulatory cycles and estrous behavior are affected by metabolic fuel availability. Ovulatory cycles: Estrous behavior: 200 150 100 50 Lordosis duration (sec) Fed ad lib. Food- deprived
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The primary change in nutritional suppression of ovulatory cycles is a decrease in GnRH release from the hypothalamus. The pituitary works just fine. treatment with exogenous GnRH elicits normal release of LH The ovaries work just fine. treatment with exogenous LH elicits normal follicular growth and ovulation
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GnRH, and consequently LH, is secreted in a pulsatile fashion.
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