[Leptin in the endocrinology of obesity]

The article summarizes the endocrinology axis in relation to leptin in the obesity. There is a glucocorticoid hypothesis in the obesity origin. Human plasma leptin levels are elevated in Cushing's syndrome and there is a robust leptin secretory responses to dexamethasone. Obesity impacts on reproductive function in man and women. Leptin levels are higher in women than in men and a critical blood leptin level is necessary to trigger reproductive ability in women. The relationship between body mass index and circulating leptin varies during the course of spontaneous cycles in women, the best correlation occurring during the luteal phase when progesterone and leptin concentrations are highest. Obesity is associated with a decrease in growth hormone (GH) and reversible with weight loss. The influence of body composition on GH secretion in the obesity may be mediated through leptin, acting as a peripheral signal from adipose tissue. Thyroid dysfunction appear not associated with alterations in serum leptin levels. There is a significant relationship between insulin and leptin, but it is not immediate, since type 2 diabetics show similar leptin levels to those of nondiabetic humans of the same body mass index.