Thyroid autoimmunity role in the evolution of endemic goiter in rural area, Fars, Iran.

Abstract

WHO reports indicate no iodine insufficiency in Iran, however, goiter is still endemic in Fars Province. This study evaluates the role of thyroid autoimmunity in the evolution of endemic goiter. A total of 516 permanent residents of Akbarabad County of the Kavar area in Fars Province, Iran were selected by simple random sampling. Patients with thyroid malignancy and dysfunction, and those who consumed drugs affecting thyroid function were excluded. After signing a written consent form and undergoing a thyroid examination, 5 cc of blood were drawn to measure free T3 and T4 (RIA), TSH (IRMA), and anti-thyroid peroxidase (competitive RIA) levels. Moreover, samples of 50 cc morning urine were collected for the measurement of urinary iodine excretion (UIE; chloridric acid digestion). Data were analyzed by SPSS (version 13). P<0.05 was significant. The prevalence of goiter was 38.4% by WHO classification. The prevalence of children with UIE 2-4.9 µg/dL was 5.8%, which indicated sufficient iodine intake. Goiter was more prevalent in females, as well as in patients with positive anti-TPO or higher TSH titers (P<0.01). The prevalence of positive anti-TPO was higher in goiterous patients than healthy persons (P=0.002), which increased with an increase in age, grade of thyromegaly or TSH (P<0.02). Regression analysis showed the odds ratio for diagnosing goiter in females was 2.4 (P<0.001), in those with positive anti-TPO it was 1.87 (P=0.03) and in those with TSH>5.2 mIU/mL the odds ratio was 2.74 (P=0.01). In adolescents compared to children the odds ratio was 0.36 (P=0.01) and the odds ratio in adults to children was 0.33 (P=0.001). This study indicates that despite normal UIE, goiter is endemic in Akbarabad County. Some degree of goiter endemicity may be due to thyroid autoimmunity.