In an attempt to study age-related metabolic abnormalities, glucose intolerance and serum insulin were examined in normal subjects and hyperthyroid patients. For comparison, serum concentrations of thyroxine (T4), triiodothyronine (T3), and total cholesterol were also measured in normal subjects and hyperthyroid patients.
Although serum T4 concentration remained unchanged, serum T2 concentration decreased significantly in an elderly group of normal subjects. Similarly, serum T4 did not change with age and serum T2 decreased slightly but progressively with age in hyperthyroid patients. In addition, serum total cholesterol concentration increased progressively with age in normal subjects.
Oral glucose tolerance decreased with age in normal subjects despite the same timing, peak level attained, and total magnitude of insulin response for old and young subjects. Although the severity of hyperthyroidism decreases with age, age-related glucose intolerance was much more apparent in hyperthyroid patients because of the age-related decrease of basal concentration, the peak level attained, and the total magnitude of insulin response. It is suggested that age-related glucose intolerance is magnified by the hyperthyroid state.