Age-related changes of thyroid function and immunologic abnormalities in patients with hyperthyroidism due to Graves'...

In order to clarify the reasons why hyperthyroidism due to Graves' disease is mild in aged patients compared to young patients, we examined the degree of hyperthyroidism and immune abnormalities in 371 untreated patients. The patients were divided into nine groups based on their age; groups A to I consisted of patients aged 0-9, 10-19, 20-29, 30-39, 40-49, 50-59, 60-69, 70-79, and 80-89 years, respectively. Serum thyroxine (T4), triiodo-thyronine (T3), and thyroglobulin levels were highest in group B (patients aged 10-19 years) and decreased progressively with advancing age. T3/T4 ratio was also highest in group B and decreased progressively with age. These data reconfirmed that the degree of hyperthyroidism is milder in older patients. The prevalence of positive microsomal and thyroglobulin antibodies was highest in group B (patients aged 10-19 years) and progressively lower in older groups, suggesting that an association with Hashimoto's thyroiditis is less prevalent in aged patients. We suggest that hyperthyroidism due to Graves' disease is mild in aged patients because responsiveness of the thyrocyte to the abnormal stimulator, thyrotropin-receptor antibody, may be reduced. Such reduced responsiveness may not be due to Hashimoto's thyroiditis, since the prevalence of antithyroid antibodies is lower in aged than in younger patients with hyperthyroidism due to Graves' disease.