Effect of hyperthyroidism and hypothyroidism on rat red blood cell insulin receptors and catecholamines: relationship with cellular ageing.

Insulin receptor activity and its relationship with catecholamines in rat young, middle aged and old red blood cells were investigated in experimental hypothyroidism and hyperthyroidism. In control animals, a loss of insulin receptor activity was found with cellular ageing and increased levels of norepinephrine, epinephrine and glycosylated hemoglobin. There was down regulation of insulin receptors together with alterations in membrane bound catecholamines in thyroid hormones imbalances. These results suggest that loss of insulin receptor in cellular ageing is probably part of a more generalised alteration and rat serves as an excellent model in defining the role of thyroid hormones in carbohydrate tolerance.