Leptin levels and luteinizing hormone pulsatility in normal cycling women and their relationship to daily changes in metabolic rate

ObjectiveTo determine whether leptin and LH secretion in normal women is related to changes in metabolic rate.SettingAcademic medical center.Patient(s) and DesignTen young women with normal weight and menses were studied during the early follicular phase. Leptin and LH levels were sampled every 15 minutes over a 24-hour period. Metabolic rate was frequently sampled using indirect calorimetry. Luteinizing hormone pulsatility was analyzed using a Cluster Program analysis.Intervention(s)None.Main Outcome Measure(s)Leptin, LH, and metabolic rate levels.Result(s)All subjects demonstrated a diurnal leptin curve. Luteinizing hormone pulses were increased in amplitude and slower after the leptin peak. The average (±SE) number of LH pulses per 6 hours slowed from 4.30 ± 0.42 to 3.00 ± 0.42 pulses after the leptin peak, whereas pulse amplitude increased from 1.64 ± 0.26 to 2.51 ± 0.42 mIU/mL after the leptin peak. The LH interpulse interval increased from 85.1 ± 3.64 minutes to 108.8 ± 10.26 minutes after the leptin peak. Metabolic rate began to drop approximately 4–6 hours before leptin levels peaked, going from 1.66 ± 0.24 to 1.15 ± 0.04 kcal/min after the leptin peak.Conclusion(s)There is a significant association between the timing of the leptin peak, the nightly slowing of LH pulses, and the fall in metabolic rate, suggesting a metabolic cycle in normal individuals.