Leptin (Greek leptos meaning thin)'s a 16 kDa protein hormone that plays a key role in regulating energy intake and energy expenditure, including appetite and metabolism. Leptin's one of the most important adipose derived hormones. The Ob(Lep) gene (Ob for obese, Lep for leptin)'s located on chromosome 7 in humans. Discovery The effects of leptin were observed by studying mutant obese mice that arose at random within a mouse colony at the Jackson Laboratory in 1950. These mice were massively o… (More on Leptin)