PREVALENCE OF SERUM ANTITHYROID PEROXIDASE ANTIBODIES IN 85-YEAR-OLD WOMEN AND MEN

Antithyroid peroxidase antibodies (TPOAb) were determined by competiti ve radioassay in serum samples obtained from a representative populati on of 85-year-olds (601 women and 285 men). The prevalence of increase d TPOAb concentration was significantly higher in the women. In indivi duals without previously known thyroid dysfunction, 16% of the women a nd 9% of the men had TPOAb concentration > 100 kilo-units/L, the upper decision limit. We found a direct relationship between TPOAb and thyr otropin (TSH) concentrations and an inverse relationship between TPOAb and free thyroxine (T-4) concentrations, but no relationships between TPOAb and defined disorders or treatment with pharmaceutical drugs. E xclusion of individuals with increased TPOAb concentration and conditi ons influencing TSH and free T-4 concentrations resulted in a decrease of the upper reference limit for TSH concentration and an increase of the lower limit for free T-4 concentration, indicating that high TPOA b concentration should be taken into account when evaluating normal re ference intervals for thyroid-function tests in the elderly.