Ultrasonographic Analysis of the Thyroid Gland during Pregnancy

The aim of the study was to determine whether pregnancy induced ultrasonographically detectable changes of the thyroid gland. It is a very interesting clinical feature, because some parts of inland Croatia were an endemic goiter area before the implementation of the 1996 act on salt iodination. Sixty-six pregnant women with no history of thyroid disease were repeatedly examined by ultrasound during the course of pregnancy. The size and echostructure of the thyroid were estimated. The thyroid volume increased slightly during pregnancy, but mostly remained within the normal range for particular age. A significant thyroid volume enlargement was observed in third trimester as compared with either first trimester (p=0.02) or control group (p=0.01). Mild goiter of 16% was found in pregnant women in comparison to control group. Morning urine sample, thyroid hormone, TSH and thyroid antibodies were also analyzed in 89 women. Median urine iodine was 8.8 μg/dL. Sixty percent of pregnant women had an iodine concentration below 10 μg/dL. In four out of nine subjects with goiter, urinary iodine excretion was below 5 μg/dL. Elevated serum TSH concentration was recorded in three (3%) women, however, they were euthyroid at the time of the study. Results of the study supported the hypothesis that thyroid volume and thyroid function adapt to the physiologically increased iodine and energy demands. The possible goitrogenic effect of pregnancy could be prevented by an increased iodine intake by diet rich in iodine.