Thyroid volume and serum calcitonin changes during pregnancy

Pregnancy has a profound impact on thyroid homeostasis which results in change of thyroid function and thyroid volume (TV). Moreover, calcitonin (CT), and its gene-related peptide have been demonstrated to play an important role in the implantation process.

To evaluate changes in TV and serum CT levels during pregnancy.

One hundred and fifty-five pregnant women were consecutively enrolled at the first trimester of gestation and underwent clinical, biochemical and sonographic assessment at enrollment, at the second and third trimesters and at 6 months after delivery.

Throughout gestation serum TSH exceeded the upper specific first trimester cut-off in 5% of patients. TV significantly increased at the third trimester of gestation and returned to baseline levels at 6 months after delivery, while serum CT levels did not show significant changes. TV directly correlated with BMI or gestational weight gain at each trimester of pregnancy, while no significant association between serum CT levels and either weight or TV were found. Finally, in none of the patients with nodular goiter an increase in the volume of the nodules was noted. The appearance of a nodule was recorded during the second trimester in one patient.

This study confirms a prevalence of thyroid autoimmunity/hypertropinemia in 3-5% of pregnant women and shows that serum CT does not change in relation to the transient increase in TV occurring during gestation. An adequate daily iodine supplementation might be particularly useful during pregnancy to limit the TSH increase and the resulting thyroid gland and nodule enlargement.