Endocrine Abstracts

Background: Iodine deficiency disorders are a global health problem partially eliminated by salt iodization national programmes. In Poland, this micronutrient shortage diminished over the last two decades, however in some particularly vulnerable groups like pregnant and breastfeeding women additional supplementation of iodine is beneficial for both mother and newborn. The programme’s effectiveness should be regularly evaluated. The matter of concern remains the optimal recommendation of additional iodine intake in hypothyroid women.

Objectives: The study aimed to evaluate the adherence of pregnant females to recommendations and iodine intake impact on thyroid parameters of both – mothers and their newborns.

Methods: Healthy and euthyroid levothyroxine-treated women in 3^rd trimester of a pregnancy before delivery (n=91) and their newborns (n=101) were recruited to the study. The questionnaire concerning iodine supplementation was performed. Thyroid hormones analyses (TSH, ft3, ft4, a-TPO, a-Tg) measured by ECLIA were performed in mothers and cord blood of newborns, with additional assessment of screening thyrotropin (TSHs) from heel prick at the 3^rd-4^th day of life. Ioduria was assessed by maternal urinary iodine concentration (UIC), corrected by urine creatinine (ELISA) as UIC/crea ratio from a single urine sample by HPLC-UV method. This research was funded by National Science Centre in Poland (2019/33/N/NZ5/02303) as PRELUDIUM-17 grant.

Results: Supplementation of iodine was declared by 68% of women. The recruited cohort of females had median UIC (IQR) 106 (69 - 156) µg/l and UIC/crea ratio was 104 (62 - 221) µg/g, revealing iodine deficiency (according to WHO criteria UIC or UIC/crea <150). Additionally, almost 20% had UIC/crea as low as <50 µg/g. No significant difference in median UIC (IQR) was observed in patients supplemented (105 µg/l, 69-170) and non-supplemented iodine (99 µg/l, 84-130; P= 0.55). Optimal UIC/crea was reflected by the lowest TSH (P=0.02) and a-TPO (P=0.02) in mothers. TSHs above 5 mIU/l was seen in 6% of newborns.

Conclusions: The presented group of pregnant women was iodine deficient in terms of ioduria and TSHs due to WHO/UNICEF criteria. Almost one-third of women did not follow the recommendation to supplement I during pregnancy. Nevertheless, in women who declared I intake, the supplementation seemed ineffective. A sufficient iodine supply may improve the thyroid parameters of mother and newborn.