Endocrine Abstracts

Introduction: Pregnant women are at risk for selenium deficiency, which is known to maintain adequate function of immune system and thyroprotective enzymes. Same, iodine is an essential micronutrient for thyroid hormone synthesis and important endocrine regulator of early brain development. Our previous study revealed that 81% of pregnant women in Latvia have insufficient levels of iodine. The aim of the present study was to evaluate iodine and selenium supply during pregnancy in recent years, and to analyze its association with thyroid function and autoimmunity.

Methods: 123 pregnant women during the first trimester were included in a cross-sectional study in 2017–2019. Urinary iodine concentration(UIC) was measured using the ammonium-persulfate method. Thyroid status was assessed by measuring thyroid stimulating hormone(TSH), free T4(FT4), thyroid peroxidase antibodies(TPO-ab). Serum selenium level was detected in 111 participants.

Results: Out of 123 participants(age 29.23 ± 4.568;(min 17; max 40)) 65(52.8%) had UIC below the WHO recommended level of ≥150 µg/g during the first trimester of pregnancy. Furthermore, 34 patients(27.6%) were iodine deficient (UIC < 100 µg/g). The median UIC was 147.21 µg/g Cr(IQR 89.99–248.1), which is regarded as suboptimal. There was no statistically significant correlation between UIC and TSH (0.047; P = 0.618), FT4 (–-0.028; P = 0.769) or TPO-ab (0.012; P = 0.895). In addition, suboptimal iodine status did not have significant impact on thyroid function, as median TSH was 1.1 (IQR 0.676–1.45) mU/l in patients with suboptimal UIC(Group 1) and 1.0 (IQR 0.7–1.5) in patients with sufficient levels of UIC(Group 2), P = 0.816. Mean FT4 was not affected either: group 1 mean FT4–14.2 pmol/l (95% CI 13.36–15.03) and 14.14 pmol/l(95% CI 13.62–14.65) in Group 2 (P = 0.911). Moreover, it had no effect on TPO-ab levels: 28 (95% CI 27–40) vs 27 (95%CI 27–39, P = 0.612). The mean serum selenium concentration was 102.07 ± 37.01 µg/l (min 26.5; max 212.31). Furthermore, selenium concentration showed a statistically non-significant tendency of negative correlation with TPO-ab(0.027, P = 0.783) and TSH(–0.120, P = 0.217). 15 participants with increased TPO-ab(> 60) were characterized by lower levels of selenium as compared to those 93 with normal TPO-ab levels (≤ 60): 91.15(95% CI 71.07–111.23) vs. 103.10 µg/l (95% CI 95.62–110.58). There was no impact of selenium status on mean FT4(0.0, P = 0.996).

Conclusions: More than half of pregnant women had UIC below the WHO recommended level of adequate iodine supply. However, mean serum selenium level was detected to be sufficient in the first trimester of pregnancy. Yet a negative correlation between TSH, TPO-ab and serum selenium levels was found. There was no significant association between UIC, selenium status and thyroid function.

This work was supported by Grant lzp-2018/2-0059.