Iodine status of pregnant women from central Poland ten years after introduction of iodine prophylaxis programme

Abstract

Introduction: Until 1997, Poland was one of the European countries suffering from mild/moderate iodine deficiency. In 1997, a national iodine prophylaxis programme was implemented based on mandatory iodisation of household salt with 30 ± 10 mg KI/kg salt, obligatory iodisation of neonatal formula with 10 μg KI/100 mL and voluntary supplementation of pregnant and breast-feeding women with additional 100-150 μg of iodine. Our aim in this study was to evaluate the iodine status of pregnant women ten years after iodine prophylaxis was introduced.
Material and methods: A cross-sectional study was undertaken in 100 healthy pregnant women between the fifth and the 38th week of gestation with normal thyroid function, singleton pregnancy, normal course of gestation, without drugs known to influence thyroid function except iodine. Serum TSH, fT₄, fT₃, thyroglobulin (TG), anti-peroxidase antibodies (TPO-Ab), anti-thyroglobulin antibodies (TGAb) and urinary iodine concentration (UIC) were determined. Thyroid volume and structure were evaluated by ultrasonography.
Results: Fifty nine per cent of studied pregnant women had a diet rich with iodine carriers and 35% obtained iodine supplements. Twenty eight per cent appeared to have a goitre: 11 diffuse and 17 a nodular one, median goitre volume was 18.7 mL (range 6.8-29.0 mL). Median UIC was 112.6 μg/L (range 36.3–290.3 μg/L), only 28% of women had UIC ≥ 150 μg/L. Median UIC was significantly higher in the group receiving iodine supplements than in the group without iodine supplements: 146.9 μg/L v. 97.3 μg/L respectively, p < 0.001. Serum TSH, fT₃ and fT₃/fT₄ molar ratio increased significantly during pregnancy while fT₄ declined. Median serum TG was normal: 18.3 ng/mL (range 0.4-300.0 ng/mL) and did not differ between trimesters. Neonatal TSH performed on the third day of life as a neonatal screening test for hypothyroidism was normal in each case: median value was 1.49 mIU/L (range 0.01-7.2 mIU/L). Less than 3% (2 out of 68) of results were > 5 mIU/L.
Conclusion: Iodine supplements with 150 μg of iodine should be prescribed for each healthy pregnant woman according to the assumptions of Polish iodine prophylaxis programme to obtain adequate iodine supply.
(Pol J Endocrinol 2010; 61 (6): 646-651)