Effects of glucocorticoids and of growth hormone on serum leptin concentrations in man

Recent data suggest an involvement of the ob gene and its product leptin in the regulation of body fat. To assess the effects of glucocorticoids and growth hormone (GH) on serum leptin and body fat, 30 normal subjects received methylprednisolone (0.5 mg . kg(-1) day(-1)) per os for 7 days and 15 subjects received in addition sc injections of GH (0.15 IU . kg(-1) day(-1)) twice daily (combination group). Serum leptin levels increased both in the glucocorticoid group (p < 0.02) and in the combination group (p < 0.002). When body fat was estimated by bioelectrical impedance analysis it decreased during combined treatment and remained unchanged in the glucocorticoid group. Plasma insulin concentrations increased in both groups. Resting energy expenditure (indirect calorimetry) increased in the combination group and remained unchanged in the glucocorticoid group. The finding of increased serum leptin concentrations during treatment with glucocorticoid and GH suggests that serum leptin is regulated by glucocorticoids, possibly though changes in insulin secretion, independently of changes of body fat mass.