This study was designed to investigate the effects of Melanocyte stimulating hormone MSH on serum testosterone T and estradiol E2 hormones concentrations in alloxan-induced diabetic rats. Eighty male and female Sprague Dawley rats, weighing 180-200 g, were divided into four groups of normal rats and four groups of alloxan-induced diabetic rats were given intraperitonially (i.p.) a daily injection of 20 mg alloxan solution/100 g of body weight for 10 days. Two groups, male and female from the normal and 2 diabetic groups served as controls and did not inject with MSH 2 groups, male and female from the normal rats and 2 groups from the diabetic rats injected (i.p) daily with MSH at a dose of 2-microg/100 g of body weight, for 10 days. The control group was only injected with the same volume of normal saline. Serum glucose concentrations were higher and serum insulin, testosterone and estradiol concentrations were lower in diabetic rats than those in the control groups. MSH administration decreased the elevated blood glucose concentrations of the diabetic rats to the normal levels and decreased estradiol concentration in female normal rats while increased the testosterone concentration in male normal rats. Present findings indicate that MSH plays adaptive role during early stages of alloxan induced-diabetes mellitus. Further studies are needed to identify the mechanism.