Thyroid Nodules & Thyroid Cancer
Thyroid size increases during pregnancy and pregnancy has been considered to be a risk factor for increasing growth of thyroid nodules. However, it is still unclear if thyroid nodules are more commonly diagnosed in pregnant than in non-pregnant women. Generally, the diagnostic strategy for thyroid nodules is similar in pregnant and non-pregnant women, although radionuclide scans are contraindicated in pregnancy.[2,85] Upon discovering thyroid nodules, a complete family and personal history and clinical examination, including thyroid function tests should be performed.[2,85] Thyroid ultrasound is an accurate diagnostic tool that can be used in pregnancy to help determine the features and growth of nodules. Fine-needle aspiration biopsy is another safe procedure during pregnancy and pregnancy does not have an effect on its diagnostic accuracy.
Women diagnosed with differentiated thyroid cancer during pregnancy seem to have a similar prognosis if surgery is performed during or after pregnancy.[2,85] Therefore, surgery for differentiated thyroid cancer can generally be delayed until after delivery, although sonographic monitoring over the course of pregnancy is indicated.[2,85] Thyroid hormone suppression therapy may be considered for these patients, with the goal of reducing TSH to 0.1–1.5 mU/l.[2,85] If surgery is required due to thyroid cancer, the safest time to perform surgery is in the second trimester.[2,85] Benign thyroid nodules do not generally require treatment during pregnancy, unless compressive symptoms develop or if there is rapid growth.[2,85]
Women with thyroid cancer in remission on suppressive thyroid hormone therapy should continue this treatment throughout pregnancy, as subclinical hyperthyroidism does not seem to affect pregnancy outcomes.[2,35,36,72] The goals of thyroid hormone suppressive therapy depend on the persistence and recurrence risk of the cancer. TSH levels are ideally kept below 0.1 mU/l indefinitely among those with persisting disease, whereas TSH level goals are 0.1–0.5 and 0.3–1.5 mU/l among those in remission but with high and low risk of recurrence, respectively. Thyroid cancer patients generally also require increases in levothyroxine doses during pregnancy to reach these goals, but the dose increases are usually smaller than among those with primary hypothyroidism. Thyroid function tests should be conducted every 4–6 weeks in pregnancy to ensure that treatment goals are met.
Expert Rev Endocrinol Metab. 2013;8(6):537-547. © 2013 Expert Reviews Ltd.