Abstract
Objectives: We had previously shown that moderate iodine deficiency (ID), assessed by urinary iodine excretion (UIE) was frequent during late pregnancy in Nice area. We designed a prospective study to assess the prevalence of ID in normal pregnant women during the first trimester and to follow their thyroid function during the whole pregnancy with or without iodine supplementation.
Methods: Women were eligible if aged 18-40, seen before 12 weeks of gestational age (GA), without thyroid history, with strict criteria of normal thyroid tests: 12<FT4<23 pmol/l, 0.1<TSH<2.5 mUI/l, anti TPO <100. Out of 355 women seen early, 179 were potentially eligible and had thyroid screening: 89 were not included: 51 refused to participate, 28 had tests slightly off our criteria, 7 had normal tests but were ATPO+, 3 had abnormal tests (1hyper, 2 hypothyroidism). 90 women (27.7y ± 5, GA 8weeks ± 2) have been included. Initial evaluation included standardized questionnaire, thyroid ultrasound, full thyroid tests, including UIE.
Results: expressed as medians (range). FT4: 14.25 pmol/l (12-19); TT4: 111.3 nmol/l (66.6-167.4); TSH: 1.17 mUI/l (0.13-2.46); FT3: 5 pmol/l (3.85-6.63); TBG: 27.41 µg/ml (18.54-49); Tg 17.85U/ml (1.3-100); thyroid volume 9.43 ml (4.5-17.8); UIE (n=78) 126.5 µg/l (7.5-2838). 40% of women had ID defined as UIE<100 and 61.5% as UIE<150. 1.3% had severe ID <20, 20% adequate iodine intake, 18% more than adequate including 3 with excessive intake (ioduria>500). UIE correlated positively with TT4 (r=0.25, p=0.027), negatively with age (r=-0.23, p=0.04) and thyroid volume (r=-0.22, p=0.05). There was a negative trend with TSH (r=-0.2, p=0.08).
Conclusions: ID is present in 40 to 60% (depending threshold of ID) of healthy pregnant women during the first trimester in Nice area. Only 20% had UIE suggesting adequate recommended intakes. Interestingly, 18% in that cohort would not need any iodine supplementation, based on one spot urine test.