Background & Aims: This study was aimed to assess the interrelationship between urinary iodine excretion (UIE) and thyroid stimulating hormones (TSH) levels in pregnant women during the first trimester. Materials & Methods: Women (n=485 age: >14 years old without any history of thyroid dysfunction) were recruited at their first prenatal consult before 12 weeks of amenorrhea. Proportion of participants from urban and rural population were 41.6% (n=223) and 58.4% (n=283). Random urine and blood samples were collected for the analysis of UIE and TSH, respectively. Results: The overall median UIE was 74 μg/L and 86.4% of women had iodine deficiency (ID) as defined by UIE < 150. The respective levels for urban and rural populations were 76 μg/L vs. 64 μg/L and 88.5% vs. 83.3%. Median TSH as a whole was 0.8 mIU/L whilst those for urban and rural subjects were 1 mIU/L and 0.7 mIU/L. No correlation was seen between UIE and TSH levels. Conclusions: Our data reveals that sever ID is present in 33% of the subjects during the first trimester and that TSH levels are 12-64% lower than those reported for with adequate or more than adequate iodine intake regions in Iran. This preliminarily result suggest that whole body iodine stores is probably adequate to prevent hypo-thyroxinemia during early pregnancy in regions with mild to moderate iodine deficiency. SOURCE: URMIA MED J 2013: 24(10): 752 ISSN: 1027-3727

Keywords: Pregnancy, Thyroid function, Thyroid stimulating hormone (TSH), Urinary iodine, Iodine deficiency

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