Thyroid Disease During Pregnancy

Options for Management

Tuija Männistö

Disclosures

Expert Rev Endocrinol Metab. 2013;8(6):537-547. 

In This Article

Thyroid Nodules & Thyroid Cancer

Thyroid size increases during pregnancy[1] and pregnancy has been considered to be a risk factor for increasing growth of thyroid nodules.[2] However, it is still unclear if thyroid nodules are more commonly diagnosed in pregnant than in non-pregnant women.[2] 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.[2] Fine-needle aspiration biopsy is another safe procedure during pregnancy and pregnancy does not have an effect on its diagnostic accuracy.[2]

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,[2] 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.[2] 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.[2] 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.[51] Thyroid function tests should be conducted every 4–6 weeks in pregnancy to ensure that treatment goals are met.[2]

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