Is leptin the primary signal to awaken the reproductive system at puberty? The ability of exogenous leptin to initiate puberty prematurely would seem to strengthen support for the ‘‘critical body fat’’ hypothesis of sexual development. Two studies demonstrate an advancement of pubertal onset in female mice by leptin treatment. Chehab et al. treated mice beginning on postnatal Day 21 with daily i.p. injections of leptin (2 ^g/g BW) or PBS. Leptin-treated animals showed 1-4 days advancement of VO, increased reproductive organ (uteri, ovaries, oviducts) weights, and decreased latency to first mating compared to PBS-treated animals. However, a footnote to this study states that the authors had difficulty replicating their observation of a leptin-induced advancement of VO. buy flovent inhaler
In a similar study by Ahima et al., mice given the same dose of leptin showed early onset of VO, vaginal estrus, and vaginal cycling compared to vehicle-treated mice, without undergoing significant weight loss. It should be noted that leptin treatment does not seem to advance pubertal onset in female rats, and experiments performed in this laboratory have been unable to confirm the results of Chehab et al. and Ahima et al. in female mice (unpublished observations). Given the conflicting reports in the literature and our own studies of this question, we believe it is more likely that leptin is a factor permissive to the onset of puberty, and that, although some minimal threshold level of leptin is necessary to pubertal development, leptin by itself is not sufficient to initiate puberty.