The response of the hypothalamic-pituitary-gonadal axis to fasting is modulated by leptin.

Reproductive function is intimately related to caloric consumption. During fasting states, the hormones regulating reproduction, those of the hypothalamic‐pituitary–gonadal axis, in particular, are severely altered. With the exciting observations that the obese (ob) gene product, leptin, may also modulate neuroendocrine functions, we examined leptin's ability to prevent the consequences of fasting on reproductive hormones. Two groups of male rats, aged 65 days old, were either fasted and saline‐injected or fasted and leptin‐treated for approximately three days. Another group was given free access to rat chow. Leptin was able to prevent the fasting‐induced fall of serum testosterone. Similar to testosterone's dependence on leptin, leptin concentrations were somewhat dependent on testosterone. Castration accelerated the normal, age‐related increase in serum leptin. Leptin also prevented the fasting‐induced fall in luteinizing hormone (LH). The increase of β‐LH mRNA seen in the fasting state was prevented by...