The involvement of Transforming Growth Factors in regulation of cellular function in male diabetic rats’ testes is less understood. Adult male Sprague-Dawley rats (120 – 140gm) were divided into 3 groups. Control group (n = 7); fed on normal rat pellets. Streptozotocin diabetic group (n = 7); received a single IP injection of streptozotocin 45 mg/kg BW (Guneli et al., 2008) in Na+ citrate buffer pH 4.5. Insulin resistant group (n = 7); fed ad libitum on special diet containing 25% fructose W/W for 12 weeks (Arikawe et al., 2006; Arikawe et al., 2012). Following hyperglycaemia confirmation, blood samples were collected under light anaesthesia (IM ketamine, 10mg/kg) for serum activin and inhibin (Transforming Growth Factor β) Concentrations. Animals were perfused with 4% Paraformaldehyde (PFA). Testes were isolated and fixed in 4% PFA overnight and embedded in paraffin. 5µm thick sections were made and mounted on poly-L-lysine coated slides. Immunohistochemical analysis was assessed using Androgen receptor (C-19) and Sox-9 antibodies (Santa Cruz Biotechnology, USA) through light microscopy. Serum inhibin was significantly lower (P < 0.05) in the insulin resistant group compared to the control and streptozotocin groups. There was no significant difference in serum activin concentrations amongst the three groups. C-19 and Sox-9 indexes were significantly lower (P < 0.05) in both experimental groups compared to control group. The results of the study indicate that streptozotocin and insulin resistance affect Leydig and Sertoli cell function.