Leptin replacement in patients with leptin gene mutations improves hypogonadotropic hypogonadism. The effects of leptin replacement on luteinizing hormone (LH) secretion in patients with lipodystrophy are unknown. We examined nocturnal LH secretory dynamics on and off exogenous leptin therapy using a 2-period, nonrandomized study that included leptin-naïve and leptin-treated subjects with lipodystrophy. In period 1 (5 days) the leptin-treated group (n= 4) continued leptin; leptin was then withdrawn for the next 14 days (period 2). Leptin-naïve subjects (n= 8) were studied without leptin in period 1 and with leptin replacement in period 2. LH secretory dynamics were assessed (23: 00-07: 00 h, sampling every 10 min, analyzed by multiparameter deconvolution algorithm) at the end of each period. Mean (on vs. off: 5.0±3.1 vs. 3.2±1.3 IU/l, p= 0.04) and integrated LH concentrations (2,403±1,495 vs. 1,534±642 IU× l-1× min-1, p= 0.04) were higher on leptin therapy. Leptin treatment increased burst mass (9.7±15.4 vs. 7.0±11.2 IU/l, p= 0.03) and tended to nonsignificantly increase LH burst frequency (0.77±0.26 vs. 0.67±0.24 h-1, p= 0.08). Consequently, leptin therapy increased the pulsatile production rate (64±101 vs. 57±73 IU× l-1× 8 h-1, p= 0.01). On leptin, testosterone (507±286 vs. 360±174 ng/dl, p= 0.09) and estradiol levels (74±36 vs. 29±24 pg/ml, p= 0.01) were higher in males and females, respectively. Leptin increases spontaneous nocturnal LH secretion in patients with lipodystrophy. This is consistent with rodent and in vitro studies showing a direct stimulatory effect (hypothalamic, pituitary or both) of leptin on LH secretion. These novel findings may explicate some of the salutary effects of leptin therapy on the hypothalamic-pituitary-gonadal axis in lipodystrophy.