| A significant proportion of women in the population have circulating thyroid antibodies but normal thyroid function. The presence of these antibodies correlates with underlying focal thyroiditis and may lead to thyroid failure. The prevalence of antibodies is very dependent on the techniques used but regardless of the methodology all studies acknowledge that the frequency is higher and increases progressively with age in women compared with a low prevalence and no particular age trend in men. The prevalence of anti-thyroid microsomal antibodies/anti-peroxidase antibodies has been shown to increase from approximately 3% in young women to over 15% in women in the 6th decade of life. The underlying mechanisms responsible for initiating thyroid autoantibodies and promoting progression of the disease remain largely unknown (4). There is a strong association between the presence of thyroid antibodies and raised TSH indicating some degree of thyroid failure. Over the twenty year follow-up of the Whickham survey, 17% of women and 7% of men who initially had no antibodies became positive, 9% of women and 2% of men had remained positive and 2% of women and 0.5% of men no longer had positive tests. There was no evidence that a positive antibody test in the original survey was a factor for premature death in the cohort study. Over half of the women whose tests had changed from positive to negative were receiving thyroxine replacement therapy for hypothyroidism. |
