Leptin--a critical body weight signal and a "master" hormone?

Leptin, initially identified as a hormone produced by white fat that acted as a satiety signal, has since been found to be synthesized in various tissues and to subserve diverse functions, including regulation of blood glucose concentrations and blood vessel growth, and signaling to the reproductive and immune systems. Recent research suggests that leptin, acting through the sympathetic nervous system, may also regulate bone density. Trayhurn discusses this research in the context of the established bidirectional interaction between leptin and the sympathetic nervous system, and the need to elucidate a unifying theme with which to make sense of leptin's myriad, seemingly quite disparate, functions.