Effects of different iodine nutrition status on thyroid function in pregnant women and newborns / 中华地方病学杂志

ABSTRACT

Objective:To investigate the correlations of dynamic iodine nutrition status and thyroid function in pregnant women and newborns in Lingang of Shanghai, so as to provide an evidence for whether urine iodine testing and iodine supplementation should be carried out.Methods:A prospective study was conducted by randomly selecting pregnant women from October 2017 to October 2018 in Shanghai Sixth People’s Hospital East Affiliated to Shanghai University of Medicine & Health Sciences. The pregnant women were divided into early (5-12 weeks), middle (22-24 weeks), late pregnancy (36-37 weeks). Samples of serum and 24 hours urine were collected to test on thyrotropin (TSH), free thyroxine (FT 4), free triiodothyronine (FT 3), anti-thyroid peroxidase (TPOAb), anti-thyroglobulin (TgAb) and urinary iodine. TSH in neonatal heel blood was analyzed 72 h after birth (newborns from pregnant women in the late pregnancy). The differences of thyroid function of pregnant women with different pregnant periods and different urinary iodine levels were analyzed, as well as the neonatal TSH levels of pregnant women with different urinary iodine levels. Results:A total of 109, 90 and 54 cases of pregnant women in early, middle and late pregnancy were investigated and the medians of urinary iodine were 120.95, 136.30 and 116.80 μg/L, respectively. There was no significant difference in urinary iodine content among different pregnant periods( P > 0.05). The proportions of urinary iodine level less than 150 μg/L in early, middle and late pregnancy were 75.2% (82/109), 61.1% (55/90) and 59.3% (32/54), respectively. The median values of serum TSH in early, middle and late pregnancy were 1.81, 1.95 and 2.29 mU/L, mean values of FT 3 were (5.21 ± 0.84), (4.79 ± 0.72) and (4.13 ± 0.56)pmol/L, and means of FT 4 were (16.48 ± 2.58), (15.02 ± 2.78) and (13.31 ± 1.87) pmol/L, respectively. The FT 3 and FT 4 levels in the late pregnancy were lower than those in the early and middle pregnancy, while the TSH levels in the late pregnancy were higher than those in the early and middle pregnancy. There were no significant difference in serum FT 3, FT 4 and TSH levels among early, middle and late pregnancy under different urinary iodine levels. The median TSH of newborn heel blood was 1.48 mU/L. There was no statistically significant difference between the neonatal heel blood TSH level of pregnant women with urinary iodine < 150 μg/L [1.45(1.09, 2.23)mU/L] in late pregnancy and those with urinary iodine ≥150 μg/L [1.42 (1.14, 2.61) mU/L, Z=- 0.354, P > 0.05]. Conclusions:There is mild iodine deficiency in pregnant women in Lingang of Shanghai. However, due to the compensatory regulation, it has no significant effect on the thyroid function of mother and newborn. Monitoring of iodine nutrition of pregnant women should be carried out and iodine supplementation should be done scientifically and reasonably.