Thyroid Dysfunction of North Korean Women Living in South Korea, Focusing on Subclinical Hypothyroidism

ABSTRACT

BACKGROUND: Thyroid function depends on ethnic and environmental factors. North Korean refugees have the same genetic background as South Koreans, but they have been exposed to different environments. This study examines the prevalence and pattern of thyroid disorders in North Korean women living in South Korea, focusing on subclinical hypothyroidism (SCH). METHODS: The intended sample was a total of 327 North Korean women residing in Seoul. Health questionnaires and medical examinations, including serum thyrotropin (thyroid stimulating hormone, TSH), free thyroxine, and thyroid autoantibodies, were conducted. RESULTS: The prevalence of SCH was 9.4%. In logistic regression analysis, smoking, menopause, length of stay in South Korea, body mass index, history of thyroid disease, and metabolic syndrome were not associated with the risk of SCH. Whereas, the positivity of autoantibodies were associated with a high risk for SCH (odds ratio [OR], 4.840; 95% confidence interval [CI], 1.80-13.017; P = 0.002), and age was associated with a low risk for SCH (OR, 0.94; 95% CI, 0.888-0.994; P = 0.031). The serum TSH levels also decreased with increasing age, and in particular, there was significant difference between 30-39 years, and over 60 years (2.33 +/- 1.51 microIU/mL vs. 1.54 +/- 0.73 microIU/mL, P = 0.028). CONCLUSION: In North Korean women, the positivity of autoantibodies was associated with a high risk for SCH. But interestingly, a younger age was associated with a high risk for SCH. Considering that they suffered from severe famine at the period of growth, and this led to malnutrition, their thyroid dysfunction might be associated with the peculiar environment that they experienced.