Hyperthyroidism in molar pregnancy: β-HCG levels do not always reflect severity

Molar pregnancy is a complication characterised by abnormal benign or malignant proliferation of trophoblastic cells resulting in markedly elevated β-hCG (human chorionic gonadotrophin) levels, an established marker for the presence of the disease. Owing to the structural homology between β-hCG and TSH, the raised β-hCG can result in secondary hyperthyroidism.

Two patients aged 20 (Case 1) and 31 years (Case 2) presented to the emergency department within a few days of each other complaining of vaginal bleeding associated with abdominal pain. Ultrasound evaluation, β-hCG and thyroid function tests were performed on both patients.

Both had elevated β-hCG levels and ultrasound evidence of molar pregnancy and were diagnosed with gestational trophoblastic disease (GTD) associated with hyperthyroidism based on thyroid function test results. Case 1 had lower β-hCG levels and free T4 levels compared with Case 2 but clinical assessment of the former revealed severe illness and more complicated course with the development of a thyroid storm. Case 2 had β-hCG levels almost double those of Case 1, yet was stable and her levels decreased much faster, reaching and maintaining undetectable levels.

These cases demonstrate that the β-hCG levels do not always correlate with disease severity and prognosis in patients with GTD.