Comparative screening for thyroid disorders in old age in areas of iodine deficiency, long-term iodine prophylaxis and abundant iodine intake

OBJECTIVE To investigate the effect of varying amounts of iodine intake on the prevalence of thyroid dysfunction, autoimmunity and goitre in old age. DESIGN The first screening study where elderly subjects with varying amounts of iodine supply but from the same geographical and ethnographical region (Carpathian basin) were compared, and all hormone measurements and ultrasonography were performed by the same laboratory or person. PATIENTS Nursing home residents were screened for thyroid disorders from: (A) an iodine‐deficient area, Northern Hungary (n = 119; median age 81 years; median iodine excretion (MIE) 0.065 μmol/mmol creatinine (equivalent to 72 μg/g creatinine); (B) an area of obligatory iodinated salt prophylaxis since the 1950s, Slovakia (n = 135; median age 81 years, MIE 0.090 μmol/mmol creatinine (equivalent to 100 μg/g creatinine)) and (C) an abundant iodine intake area, Eastern Hungary (n = 92; median age 78 years; MIE 0.462 μmol/mmol creatinine (equivalent to 513 μg/g creatinine)). MEASUREMENTS TSH, T4, free T4, T3, thyroglobulin (Tg), antibodies to Tg (AbTg) and to thyroid peroxidase (AbTPO), iodine excretion, ultrasonography of the thyroid gland. RESULTS In regions A, B and C, the prevalence of unsuspected clinical hypothyroidism was 0.8%, 1.5% and 7.6% (P = 0.006), with all cases except one being antibody positive (Ab+). The occurrence of subclinical hypothyroidism was 4.2% in region A, 10.4% in region B and 23.9% in region C (P