Transient gestational hyperthyroidism in a pregnant woman with monochorionic twins complicated by twin-to-twin transfusion syndrome (Case report)

Monochorionic multiple pregnancy complicated by transfusion syndrome (MCTP) is associated with higher maternal serum levels of both hCG and thyroid hormones. There are virtually no data on the clinical consequences of MCTP for the mother and fetus in this situation.
Case report. A 32-year-old multiparous patient with monochorionic diamniotic twins with stage III MCTP was admitted to the Research Institute of Obstetrics and Maternity Care at 21-22 weeks of pregnancy with complaints of weakness, dyspnea at rest, tachycardia up to 180 bpm. There were no indications of thyroid disease. Antibodies against thyroid peroxidase and TSH receptors were not detected. TSH level 0.007, CT3 128 pmol/l, CT4 162 pmol/l. Thyroid ultrasound was unremarkable. To reduce the heart rate, beta-blocker therapy was started. Selective laser coagulation of placental anastomoses was performed in the volume of 19 AV, 4 AA, 2VV. Amnioreduction was 2500 ml. A 2-fold decrease in the hCG level was noted after 2 weeks, and after another 2 weeks, the hCG levels reached normal values for the period in multiple pregnancies. Within 2 weeks after the operation, the patient’s pulse normalized, shortness of breath and weakness decreased.
Сonclusion. This clinical case demonstrated a change in the mother’s thyroid function in TTTS before and after laser therapy. In the differential diagnosis of causes of thyrotoxicosis in pregnant women, endocrinologists and obstetricians should consider hCG-mediated hyperthyroidism associated with TTTS, since this condition is not expected to resolve spontaneously until fetoscopic laser coagulation of placental anastomoses is performed.

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