6-17-08 - 6/17/08 Hypotheses about puberty: 1.) Gonadostat...

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6/17/08 Hypotheses about puberty : 1.) Gonadostat hypothesis: a.) During the pre-pubertal stage of development, the gonads release low, but constant, levels of gonadal steroids that exert a negative feedback on the hypothalamic neurons. Evidence against Gonadostat hypothesis : 1.) Experimental evidence: a.) castration of prepubertal monkeys did not lead to immediate onset of puberty (removal of inhibition) 2.) Evidence in nature: a.) males suffering from Klinefelter’s syndrome (XXY) have non-functional regressed testes, which do not produce testosterone. b.) Females suffering from Turner’s syndrome (XO) have regressed, streaked ovaries, so they do not produce estrogens or progesterone. c.) *These individuals attain puberty at the expected age just like those w/ intact functional gonads. Hypotheses about puberty: 2.) Central maturation hypothesis: a.) The hypothalamic neurons that produce GnRH require at least 12 years (post- natal) to reach maturity to produce GnRH in a pulsatile manner. This heralds the onset of puberty. Evidence supporting the central maturation hypothesis: 1.) Experimental evidence: a.) castrated, pre-pubertal monkeys, to whom GnRH was administered in a pulsatile manner, exhibited an increase in gonadotropins (indicative of pituitary response to GnRH.) b.) Intact pre-pubertal monkeys:
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This note was uploaded on 06/27/2008 for the course BSCI 342 taught by Professor Opoku during the Summer '08 term at Maryland.

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6-17-08 - 6/17/08 Hypotheses about puberty: 1.) Gonadostat...

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