IMPACT OF IODINE SUPPLEMENTATION ON SERUM TSH AND FREE T4 LEVELS IN PREGNANT WOMEN RESIDING IN MAHABAD CITY, 2015-2016

A body of evidence indicates high prevalence of maternal iodine deficiency despite adequacy of nutritional iodine status in school age children as a reference population in West Azerbaijan province. Therefore, the present investigation was designed to evaluate the impact of oral iodine supplementation (150 µg/day in the form of potassium iodate) for three months commencing at 12th week of gestation on serum thyroid stimulating hormone (TSH) and free thyroxine (FT4) concentration.
Between September 2015 and May 2016, healthy pregnant women (n=49) attending the first prenatal checkup were enrolled. Exclusion criteria were any history of thyroid dysfunction and gestation week >6 weeks. Fasting blood samples were collected before iodine supplementation at gestation weeks 6, 8, 10, 12, 14, 16 and post intervention at weeks 19, 24, 30, respectively. Serum TSH and FT4 were measured by LIAISON analyzer (DiaSorin, Italy). Data analyses were performed on SPSS software package (version 23).
Mean TSH (mIU/L) at first-, second- and third trimesters were 1.90, 2.27 and 2.3, respectively. Mean TSH before and after intervention were 1.98 and 2.43 (P This investigation reveals that iodine administration was linked with a significant elevation serum TSH levels. On the contrary, no difference was seen in the FT4 concentrations. Prevalence of individuals with normal TSH and FT4 before and after iodine administration were 80.6% and 71.4% vs 78.6% and 83.7%. The transient alternation in TSH and FT4 concentrations after iodine administration is probably related to the surge in iodine (Wolff- Chaikoff effect). Further analyses are needed to get an insight into the impact of iodine supplementation on the thyroid hormone profile during pregnancy.