Clinical characteristics and thyroid function in complete hydatidiform mole complicated by hyperthyroidism.

OBJECTIVES: To identify possible clinical factors associated with hyperthyroidism at presentation and to assess post-evacuation thyroid function in women with complete hydatidiform mole (CHM). METHODS: This observational study included women with CHM attending a specialized Brazilian center in 2002-2018. Clinical and laboratory data (serum hCG, TSH, fT4) were collected at presentation. Factors associated with hyperthyroidism were assessed by logistic regression. Receiver-operating characteristic curves were built to determine the hCG cutoff for predicting hyperthyroidism at CHM presentation. Post-molar evacuation follow-up included clinical assessment and close thyroid function monitoring. RESULTS: Of 137 CHM patients, 69 (50.3%) had hyperthyroidism of any type (43.5% subclinical, 56.5% overt) at presentation. Uterine fundal height > 16 cm or > gestational age (GA), and theca lutein cysts >6 cm were significantly associated with both subclinical and overt hyperthyroidism. The optimal hCG cutoff for predicting hyperthyroidism was 430,559 IU/L (sensitivity 85.5%, specificity 83.8%). Post-evacuation hyperthyroidism/transient hypothyroidism conversion was observed in 13% of the women with hyperthyroidism at presentation. Among the patients not showing conversion to hypothyroidism, median time for TSH normalization was 2 and 3 weeks for subclinical and overt hyperthyroidism, respectively. In the women with overt hyperthyroidism, fT4 was normalized at 2 weeks. CONCLUSIONS: Uterine fundal height > 16 cm, uterine fundal height > GA, theca lutein cysts >6 cm, and hCG >400,000 IU/L at presentation are associated with greater risk of hyperthyroidism and its complications. Close monitoring thyroid function during postmolar follow-up showed that, as thyroid hormones are normalized within 2-3 weeks post-evacuation, the use of beta-blockers or antithyroid drugs can be rapidly discontinued.