Objective To investigate the effect of enhanced iodine supplementation on iodine nutrition and thyroid function in women of childbearing age.

Methods A total of 100 women of childbearing age who received oral iodized oil capsules once or twice a year in Kashgar and Aksu of China were selected as experimental group, and 100 women who did not receive iodized oil capsules in Yili of China were selected as control group. Urine and blood samples were collected to measure urinary iodine and five indices of thyroid function, i.e., free triiodothyronine (FT3), free thyroxine (FT4), thyroid stimulating hormone (TSH), thyroglobulin antibody (TGAb), and thyroid peroxidase antibody (TPOAb).

Results The median urinary iodine of the women of childbearing age in Kashgar, Aksu, and Yili were 631.9, 320.7, and 165.4 μg/L, respectively. The women in Kashgar had a significantly lower level of FT4 than those in Yili (t=4.76, P < 0.05), while there were no significant differences in the three thyroid hormones between the women in Aksu and those in Yili (P>0.05). There were no significant differences in TGAb positive rate, TPOAb positive rate, and positive rate of both antibodies among the women in the three regions (P>0.05). There were also no significant differences in the prevalence rates of hypothyroxinemia, hypothyroidism, hyperthyroidism, and subclinical hyperthyroidism among the women in Kashgar, Aksu, and Yili (P>0.05), and the women in Kashgar had a significantly lower prevalence rate of subclinical hypothyroidism than those in Yili (2=7.28, P < 0.05).

Conclusion Oral administration of iodized oil capsules leads to a temporary excessive state of urinary iodine during the metabolic process among women of childbearing age in Kashgar and Aksu, but there is no significant difference in thyroid function among the women in Kashgar and Aksu and those in Yili. The strategy of different iodine supplementation measures for women of childbearing age is scientific and effective.