The pituitary‐testicular axis in the streptozotocin diabetic male rat: evidence for gonadotroph, Sertoli cell and Leydig cell dysfunction

The pituitary‐testicular axis was investigated in the streptozotocin diabetic male rat to determine the relationship between hormonal alterations and Leydig cell morphology. Male Wistar rats (60 days of age) were made diabetic with a single intravenous injection (65 mg/kg body weight) of streptozotocin and were studied with non‐diabetic controls at 7–11, 14, 21, and 28 days after treatment. The observations on these animals were compared to those from diabetic rats (28 days) treated with 1–2 U protamine zinc insulin/100 mg body weight. Rats with untreated diabetes had hyperglycaemia and weighed less than controls. Untreated rats also had low plasma testosterone levels associated with decreased prostate and seminal vesicle weights. Insulin treatment partially or completely prevented these abnormalities. Studies of testosterone production y perfused testis suggested Leydig cell insensitivity to LH as one possible cause of decreased androgen blood levels in diabetic rats. Lipid droplets not found in Leydig cells of normal rats were seen in diabetic animals. Plasma FSH levels were also low in untreated diabetic rats but were normal in insulin