Thyroid nodular disease (TND) is relatively common, affecting 5 of the North American population particularly women in the fertile age group.1Despite this, the reported experience with TND during pregnancy (TNDP) is meager and scanty. With infrequent exception,2thyroid cancer (TC) usually receives superficial reference in various publications dealing with cancer in pregnancy.Cancer, consisting of the breast, cervix, leukemia, lymphoma, melanoma, thyroid, ovary, and colon is the second most common cause of death during the reproductive years and occurs in 1 per 1,000 pregnancies. The current trend to delay pregnancy to a later age may favor an increased frequency of malignant disease. Pregnancy imposes limitations on the quality of cancer diagnosis and treatment so that radiologic investigation, chemotherapeutic drugs, surgical procedures, and anesthesia, all of which bear serious implications for the fetus, must be modified in some ways.Approximately 4,000 cases of cancer during pregnancy can be expected annually in the United States representing about 1 of about 400,000 women who develop malignancies and 2.2 of fertile women generally between 15 and 40 years of age. One of every 118 women who are found to harbor malignancy will be pregnant.3It has been further noted that about one half of thyroid cancers occur in women between the ages of 15 and 44. Therefore, it is surprising that in contrast to such benign conditions as thyroiditis and Graves' disease,4-7the occurrence and management of TND and TC in pregnancy has received such little attention.7,8Perhaps this indicates a physiological inhibition of TND and TC by unknown factors arising in pregnancy, but more likely it is caused by failure of the medical profession to detect TNDP.Cancer associated with pregnancy bears an unpleasant stigma. Gleicher et al.8have recognized that the immunogenetic suppression that promotes tolerance of the fetus is a common denominator for pregnancy and malignancy. The immunologic tolerance of pregnancy has been considered to be the result of suppressed cellular immunity, the presence of circulating serological blocking antibody factors, and the immunosuppressive effect of various hormones.4-7The influence of these immunological changes in the pathogenesis and course of cancer is still undefined.This chapter reviews current research into the etiological factors related to pregnancy and reproductive endocrinology which could mediate TND and TC and provide our recommendations for the diagnosis and management of these conditions in pregnancy.
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