Introduction: Aging associated with thyroid dysfunction induces many microstructural changes in the skeletal muscle fibers. These were caused by low T3, hyperglycemia and hyperinsulinemia. Triiodothyronine (T3) supplementation alleviates hyperglycemia and ameliorates insulin insensitivity of senile skeletal muscles.
Aim of the Work: Was to evaluate the histological changes of the senile albino rat gastrocnemius muscle associated with thyroid dysfunction as well as biochemical variations and the possible protective role of Triiodothyronine (T3).
Material and Methods: Thirty male albino rats were used. The rats were divided into three groups, with ten rats in each group. Adult group I; senile group II and T3 treated senile rats group III. T3 was administered at a dose of 8 μg/kg body weight for 2 weeks. At the end of the experiment, gastrocnemius muscles were dissected out and prepared for Hx&E stain, Masson's trichrome stain, Toluidine blue stained semi -thin sections and ultra-thin sections for electron microscopic study and morphometric measures were done.
Results: Skeletal muscle of senile group II showed thinning out and pyknosis of nuclei of muscle fibers. Ultrathin sections of senile rats showed abnormally-shaped degenerated mitochondria. Statistically significant decrease in thickness of muscle fibers and increase in collagen fiber deposition in group II. Group III showed restoration of the normal architecture of skeletal muscle fibers. The statistically significant increase in fasting glucose and insulin that was detected in group II was controlled in group III.
Conclusion: Aging associated with thyroid dysfunction in albino rats revealed marked structural changes in skeletal muscle and these changes were controlled by T3 supplementation through its ability to increase insulin sensitivity. This can be considered clinically to perform further studies for using T3 in geriatrics suffering from sarcopenia associated with thyroid dysfunction.