Leptin deficiency or dysfunction (LEPD) is a rare genetic disorder characterized by severe early-onset obesity, hyperphagia, and hypogonadotropic hypogonadism. It is caused by low levels of serum leptin, leading to intractable obesity from an early age. Individuals with this condition experience constant hunger, abnormal eating behaviors, and may have delayed or absent puberty due to reduced hormone production. This syndrome is associated with mutations in the LEP gene on chromosome 7q32.1.