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Unformatted text preview: by extreme duress. Hormones as a Feedback system One way in which such hormones can function as a feedback system is in reproduction. A good example of a reproductive feedback loop can be seen in ringdoves, studied by Daniel Lehrman. Gonadotropins stimulate the gonads of both males and females to produces steroids. Courtship and nest building follows this increase in gonadal steroids. Rising levels of female progesterone stimulate egg laying and incubation. At this stage, gonadotropins decrease, as do female courtship displays. Males, however, remain responsive to females at this point. After approximately one week of incubation, levels of prolactin increase in both sexes, allowing both males and females to produce a milk-like substance; gonadotropin and steroid levels decrease. When the eggs hatch and the chicks mature, prolactin levels decrease, gonadotropins increase, and the cycle begins again....
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- Winter '09