Endocrine Abstracts

Objective: The aim of the study was to assess the impact of iodine supplementation (IS) on iodine intake, thyroid function and thyroid volume (Tvol) in pregnant women (PW) from iodine sufficient region of Zagreb, the capital of Croatia. The secondary aim was to asses the impact of nodular or diffuse thyroid ultrasound (US) pattern on serum thyroglobulin (Tg) measurement.

Subjects and Methods: The study enrolled 91 PW taking IS (onIS) and 100 PW without IS (offIS) during pregnancy. Spot urine samples for urinary iodine concentration (UIC), blood samples for serum TSH, FT4 and Tg measurement and US was performed in PW in each trimester of pregnancy. Thyroid volume (Tvol) was measured with assesment of thyroid parenchima and nodules by US. UIC was measured by Seal AA3 HR (Seal Analytical, Wisconsin, USA), TSH and FT4 by CLIA (Immulite 2000 XPi Siemens) and Tg by ECLIA (Roche COBAS e411). All PW were euthyroid with negative Tg and TPO antibodies. SPSS (26.0, SPSS Inc., Chicago, IL, SAD) was used for statistical analysis.

Results: Overall median UIC, TSH, FT4, Tg and Tvol in PW onIS vs offIS were: 174 vs 158 ng/mL, 1.9 vs 1.8 mU/l, 13.2 vs 12.1 pmol/l (P < 0.05), 11.0 vs 13.6 ng/ml (P < 0.01) and 12.3 vs 13.7 mL (P < 0,05). Trimester (1^st, 2^nd, 3^rd) specific median UIC, TSH, FT4, Tg and Tvol in PW onIS vs offIS were: 173*, 177, 178 vs 155*, 163, 166 ng/mL, 1.8, 2.1*, 2.1 vs 1.7, 1.7*, 1.9 mU/l, 12.6*, 13.3*, 12.9 vs 11.2*, 12.0*, 12.6 pmol/l, 10.2, 11.0*, 11.1* vs 13.5, 14.5*, 14.5* ng/mL, 11.0*, 12.0*, 13.0* vs 12.5*, 14.0*, 14.0* mL (*P < 0,05). Nodules < 1 cm were recorded in 15 (17%) PW onIS and 24 (24%) PW offIS, and diffuse US pattern in 12 (13%) PW onIS and 17 (17%) PW offIS. Median Tg in PW onIS with diffuse and nodular US pattern vs normal US was 13.4* and 12.5 vs 10.6* mg/l (P <0.05). Median Tg in PW offIS with diffuse and nodular US pattern vs normal US was 15.7* and 15.0 vs 13.2* mg/l (P <0.05).

Conclusion: Pregnant women in the city of Zagreb, Croatia, have sufficient iodine intake regardless of IS. Iodine supplementation in pregnancy increases UIC and FT4 and decreases Tg and Tvol. Thyroglobulin is a valuable biomarker for assesment of iodine nutritional status. Nodular and diffuse thyroid US pattern increases Tg values with significant difference for diffuse pattern.