The prevalence and progression of autoimmune thyroid disease in the elderly.

Thyroid antibodies were measured by an enzyme-linked assay system (ELISA) on a random sample of 414 asymptomatic elderly people aged 70 years or more in a South Wales town in 1977. The prevalence of elevated titres of microsomal antibodies was 15.4% and of thyroglobulin antibodies 13.3%; 8.5% had an elevation of both antibodies. Five years later thyroid function was evaluated in 51 (66.6%) of those people with raised antibody titres in 1977 and compared with a control group of 46 old people drawn from the original population. Significant fluctuations of microsomal and thyroglobulin antibody titres were observed in two thirds of the antibody positive group. Three people in the control group developed positive thyroid antibodies during this period. Only 1 person in the antibody positive group became hypothyroid. The prognostic significance of raised thyroid antibodies with or without elevated TSH levels is less in the elderly than in middle aged or younger people. The significance of the fluctuating antibody levels as measured by a more sensitive method remains to be determined.