Diabetes is a metabolic disorder which affects whole body systems including reproductive system. Diabetes is also a contributing factor to infertility. Metformin is one of the most common drugs to control hyperglycemia. In this study, 36 adult Sprague-Dawley female rats (170-210 g) were divided into 3 groups (control, diabetic and diabetic-treated by metformin). In second and third groups, diabetes was induced by streptozotocin injection (45 mg kg-1, IP) and the third group was treated by metformin hydrochloride (100 mg kg-1 day-1, PO) for 8 weeks. Body weights were compared and blood glucose, gonadotropins and sexual hormones were measured. In diabetic group the blood glucose level significantly (P < 0.05) increased in comparison with that of control and metformin-treated diabetic rats. The results also revealed that, in the untreated diabetic rats, the mean body weights and pituitary-gonadal axis hormones were significantly (P < 0.05) reduced in comparison with the control. Although there were significant (P < 0.05) reduction in mean body weights in metformin-treated diabetic rats, reduction in pituitary-gonadal axis hormones was not as sharp as in untreated diabetic rats and only level of progesterone was significantly (P < 0.05) reduced in comparison with the control. The results of this investigation revealed that there was a clear relationship between experimental diabetes with body weight and pituitary-gonadal axis hormones, and treatment with metformin relatively restored diabetic complications.