Prevalence of thyroid dysfunction in a Large Southern European Population. Analysis of modulatory factors. The APNA study

CONTEXT To study the prevalence of thyroid dysfunction in a very large unselected population. OBJECTIVE To determine the prevalence of abnormal thyroid function and evaluate potential modulatory factors. DESIGN AND SETTING The Estudio de Atencion Primaria de Navarra, The APNA Study, is a cross-sectional study conducted in northern Spain. It involved 303 883 people, of 20 years of age and older, who live in the Navarra region. Participants are covered by the public healthcare system and medical records are digitalized. MAIN OUTCOME MEASURES The information was gathered from e-registered data regarding serum thyrotropin (TSH), thyroid hormones, thyroid antibody concentration and clinical context. Measurements were logged (demographic information and potential thyroid function modulatory factors). RESULTS Serum TSH (mU/L) normal range was established at 0.7-4.28. At the time of the study, 87% of the Navarra population had a TSH level within the normal range. Mean serum TSH in euthyroid individuals was higher in women (2.15) than in men (1.96) (P