IMPACT OF IODIZED OIL INJECTION DURING PREGNANCY ON THYROID FUNCTION TESTS OF OFFSPRINGS

Previous studies have shown that injection of iodized oil in pregnant women can be used as a prophylactic strategy for iodine deficiency disorders and may improve the growth indices of their offspring. Since administration of pharmacological doses of iodine may lead occasionally to large goiter and rarely to hypothyroidism, in the present study the thyroid function tests of neonates and infants born to women who had received 480 mg iodized oil intramuscularly during pregnancy were assessed and compared to those of a control group. Of 277 cord blood samples obtained from Mazandaran and Khohkiluyeh-Boyerahmad provinces, 125 made up the case (injected) and 152 the control (noninjected) group. Of 1026 blood samples of the neonates and infants from Mazandaran province, 544 made up the case and 482 the control group. Serum T4, T3 and TSH concentrations were measured with RIA kits. In the cord blood samples, mean serum T4 in cases who had received iodized oil was lower than that of the control group: 140±32 vs. 149±33 nmol/L, respectively; p<0.03. T3 and TSH were not however different. In the neonates and infants, T4 and T3 concentrations were significantly higher in the case than control group: 178±40 vs. 168±39 and 3.5±0.02 vs. 3.0±0.02 nmol/L, respecti vely, both p<0.001 1. In contrast, TSH concentrations were lower in the experimental group in comparison to control: 2.6±2.2 vs. 3.1±2.9 mU/L, respectively; p<0.001. Increased T3 and decreased TSH were seen in infants of mothers who were injected in the second and third trimesters of pregnancy. Injection of iodized oil in pregnant women does not cause hypothyroidism in the offspings, however it does cause a transient increase in serum thyroid hormones and a decrease in TSH concentrations.