Abstract:

Objective To investigate the nutrition status of iodine for pregnant women in Lanzhou,and to establish the reference ranges of serum thyroid stimulating hormone （TSH） and free thyroxine （FT₄） for pregnant women in Lanzhou. Methods The levels of urine iodine and the nutrition status of iodine in 1 290 pregnant women were determined,and the influence of different nutrition statuses on serum TSH and FT₄ in pregnant women were evaluated. The reference ranges of TSH and FT₄ were established. Results The level of urine iodine in 1 290 pregnant women was 118.0（71.0-254.0）μg/L,which was lower than that recommended by World Health Organization and the International Council for Control of Iodine deficiency Disorders（150-250 μg/L）. The levels of TSH in women with urine iodine <150 μg/L and urine iodine >250 μg/L were 2.09（0.26-6.38） and 2.15（0.19-5.84） mIU/L,respectively,which were lower than that in appropriate urine iodine（150-250 μg/L）women [2.42（0.32-7.03） mIU/L]（P<0.05）. For pregnant women,the 95% reference ranges of TSH and FT₄ were （0.15-5.56） mIU/L and （11.00-20.56） pmol/L for early pregnancy,（0.29-6.28） mIU/L and （9.86-18.38） pmol/L for middle pregnancy,and （0.81-6.98） mIU/L and （8.30-15.60） pmol/L for late pregnancy,respectively. Conclusions The nutrition status of iodine is associated with TSH in pregnant women. The reference ranges of thyroid-related hormones during pregnancy should be established according to appropriate nutrition of iodine for pregnant women.

Key words: Thyroid stimulating hormone, Free thyroxine, Reference ranges, Iodine nutrition, Pregnancy