Abstract
Thyroid cancer is the second most common cancer diagnosed during pregnancy after breast cancer. The goal of management is to control malignancy and prevent maternal and fetal complications as a result of maternal hypothyroidism. The role of female sex hormones as an etiologic factor was investigated, with no clear association. Pregnancy can cause an increase in size of a previously existed thyroid nodule through the structural similarity between TSH and BHCG, and the normally expressed estrogen receptors on thyroid gland cells. Effect of pregnancy on development and prognosis of differentiated thyroid malignancies (papillary and follicular) has also been studied. The prognosis of thyroid cancer is not worse in patients diagnosed during pregnancy or those who got pregnant after curative treatment. Termination of pregnancy is not indicated at all, surgery can be delayed till after delivery except in rapidly growing aggressive tumors. While radioactive iodine ablation is absolutely contra-indicated, the new systemic therapies are not well studied during pregnancy. However, almost all these new agents are classified as FDA category C or D and are better to be avoided. The effect of pregnancy on other types of thyroid cancer (medullary and anaplastic thyroid tumors) is not well studied because of very low incidence with pregnancy. The endocrinological management of thyroid cancer during pregnancy is of utmost importance. The hypothyroidism after total thyroidectomy can cause fetal hypothyroidism. Therefore, the management of thyroid cancer related to pregnancy needs a multidisciplinary team.