LEP and morbid obesity: Loss-of-function mutations in the leptin-encoding ob gene give rise to a complex syndrome that includes not only morbid obesity, but also abnormalities in lipid and glucose metabolism [3], haematopoiesis [4], innate and adaptive immunity (leading to increased risk of infection in mice and men) [5–9], reproduction [10], development [11], angiogenesis [12], vascular remodelling [13], blood pressure [14], and bone formation [15].