Effect of neonatal hypothyroidism on carbohydrate metabolism, insulin secretion, and pancreatic islets morphology of adult male offspring in rats

Background: Neonatal hypothyroidism has serious effects on growth, development, and metabolism. Aim: This study aims to investigate the effects of the neonatal hypothyroidism on carbohydrate metabolism, islet insulin secretion and morphology of the pancreatic islets in adult male offspring. Materials/subjects and methods: Lactating mothers of Wistar rats consumed 0.02% solution of 6-propyl-2-thiouracil during the weaning period (neonatal hypothyroid group), while mothers of the control group drank merely tap water. Body weight and survival of pups were followed up. Intravenous glucose tolerance test was performed in adult male offspring and 5–6 weeks later, glucose-stimulated insulin secretion (GSIS) was evaluated. Results: During the glucose tolerance test, plasma glucose level of the neonatal hypothyroid group (13.18±0.59 mmol/l) was significantly higher at 5 min compared to the control group (11.54±0.47 mmol/l), whereas plasma insulin concentrations and GSIS of the groups was not significantly different. Homeostasis model assessment of insulin resistance of adult male offspring of the hypothyroid group (9.1±1.0) was significantly higher as compared to the control group (4.5±0.6). Area (14,613.0±2646.3 µm2) and the diameter of the islets (147±3.0 µm) of the neonatal hypothyroid group were significantly lower, as compared to the control group (32, 886.3±4690.3 and 206.6±5.9 µm2 and µm, respectively). Conclusion: Neonatal hypothyroidism can alter carbohydrate metabolism in euthyroid adult offspring, which may increase susceptibility to the development of glucose intolerance and occurrence of Type 2 diabetes later in life.