We investigated the effect of daily intracerebroventricular (ICV) leptin administration (2-7d of neonatal age) on hypothalamic neuropeptides (NPY, - MSH) that regulate food intake, body weight (BW) gain, and the metabolic/hormonal profile in the suckling (8d, 21d) and adult (35d, 60d, 90d, and 120d) rat. ICV leptin (0.16 µg/g BW/dose; n=70) led to a postnatal decline in BW (p = 0.0002) that persisted only in the adult females (p = 0.002). The postnatal decline in BW due to leptin was associated with a decline in food intake (p = 0.01), the hypothalamic leptin receptor (p = 0.008), the neuropeptide Y (p = 0.008) immunoreactivities, and an increase in -melanocyte-stimulating hormone (p = 0.008) immunoreactivity. In addition, hyperinsulinemia (p = 0.01) with hypocorticosteronemia (p = 0.007) occurred during the postnatal period with hypercorticosteronemia (p = 0.007), hypoleptinemia (p = 0.008), and an increase in leutinizing hormone (p = 0.01) in the adult male and female progeny. Persistent hyperinsulinemia (p = 0.015) with hyperglycemia (p = 0.008) and glucose intolerance (p = 0.001) were observed only in the adult female. We conclude that postnatal leptin administration alters the adult female phenotype and speculate that this may relate to retention of leptin sensitivity resulting in a lipoatrophic state.