Prevalence of thyroid function test abnormalities and anti-thyroid antibodies in an open population in Central México.

OBJECTIVE. To examine the prevalence of abnormal thyroid function tests and positive anti-thyroid antibodies in two Central Mexican cities. MATERIAL AND METHODS. Subjects 18 to 70 years old were randomly selected to participate in this survey. A questionnaire was given and blood samples were taken to measure TSH and free T4 levels as well as anti-TPO and anti- Tg antibodies. RESULTS. The mean TSH level in subjects without existing thyroid disease was 1.72 mIU/L; 0.64 and 3.74 mIU/L were the 2.5th and 97.5th percentiles. The mean free T4 level was 1.02 ng/dL, and the 2.5th and 97.5th percentiles were 0.78 and 1.31 ng/dL, respectively. There was a 2.5% prevalence of former diagnosed thyroid diseases, 3.9% of individuals were sub-hypo, and 1.1% had overt hypothyroidism. Total hypothyroidism prevalence was 7.48% (when we considered TSH levels greater than 4.5 mIU/L), but it was 11.03% when diagnosed with TSH values greater than 3.5 mIU/L. Factors associated with hypothyroidism were older age, positive family background of thyroid disease, and positive anti- TPO and anti-Tg antibodies. Subclinical and overt hyperthyroidism were found in 1.7% of participants. CONCLUSIONS. Abnormal thyroid function test prevalence in this population was high, but few participants were aware of having a thyroid disease. The prevalence of positive anti-thyroid antibodies was high. More studies are necessary to elucidate the effects of thyroid abnormalities on other aspects of health status and quality of life.