Effects of different iodine levels on thyroid function in rats after pregnancy / 中华地方病学杂志

ABSTRACT

Objective:To investigate the effects of different levels of iodine intake on thyroid function in Wistar rats after pregnancy, and to provide experimental basis for scientific supplementation of iodine and thyroid function screening during pregnancy.Methods:One hundred and fifty female SPF Wistar rats weaned for 2 weeks were selected. Female Wistar rats were intervened with iodine nutrition by drinking deionized water containing potassium iodide (KI). According to the random number table, female Wistar rats were divided into 5 groups [severe iodine deficiency (SID) group, mild iodine deficiency (MID) group, control group (NI), mild iodine excess (MIE) group, and severe iodine excess (SIE) group, 30 rats per group]. The iodine doses of the five groups were 0.0, 1.5, 5.5, 70.0 and 350.0 μg/d, respectively. The animal model was established and intervened for 3 months to detect the 24 h urinary iodine content of rats, and compared with the NI group to determine the success of the model or not. After successful modeling, the tested female Wistar rats were mated with male Wistar rats (female : male=2-3 : 1). There were about 15 pregnant rats in each group, and continued to intervene the pregnant rats for 21 d with the same doses as the modeling conditions. The abdominal aortic blood of non-pregnant and pregnant rats was taken. After serum separation, 5 items [free thyroxine (FT 4), free triiodothyronine (FT 3), thyroid stimulating hormone (TSH), anti-thyroglobulin antibodies (TgAb), thyroid peroxidase antibody (TPOAb)] of serum thyroid function were detected in each group. Results:There was significant difference in urinary iodine content between the five groups (the medians urinary iodine were 3.540, 51.410, 286.801, 644.192 and 2 368.701, respectively, H = 94.791, P < 0.01). Rats with different iodine nutrition levels were successfully established. There were no significant differences in TSH level, TPOAb and double antibodies positive rates of non-pregnant rats among groups ( P > 0.05). There were statistically significant differences in the levels of FT 4, FT 3 and the positive rate of TgAb among groups ( P < 0.05). The level of FT 4 in SID group was lower than that in NI group ( P < 0.05). The level of FT 3 in SID group was higher than that in NI group ( P < 0.05). The positive rate of TgAb in SIE group was higher than that in NI group ( P < 0.05). There were no significant differences in TSH, FT 4 and FT 3 levels of pregnant rats among groups ( P > 0.05). There were significant differences in the positive rates of TgAb, TPOAb and double antibodies among the groups ( P < 0.05). The positive rates of TgAb, TPOAb and double antibodies in MIE and SIE groups were higher than those in NI group ( P < 0.05). The positive rate of TPOAb in MIE group was higher than that in NI group ( P < 0.05), and the positive rates of double antibodies in MID and MIE groups were higher than that in NI group ( P < 0.05). Conclusions:Iodine deficiency can lead to the change of thyroid hormone level in non pregnant rats, while iodine excess can increase the positive rate of related antibodies in non pregnant and pregnant rats.