Relapse of Human Chorionic Gonadotropin-Induced Hyperthyroidism and Severe Hyperemesis Gravidarum Secondary to Twin-Twin Transfusion Syndrome, With Rapid Recovery Following Fetoscopic Laser Coagulation: Case Report.

Background: Limited data have shown that, compared to uncomplicated twin pregnancies, pregnancies complicated by twin-twin transfusion syndrome (TTTS), a life-threatening condition, are associated with higher maternal serum levels of both human chorionic gonadotropin (hCG) and thyroid hormones. With the continuing expansion of assisted reproductive technologies, the rate of twin pregnancies, including those complicated by TTTS and associated hyperemesis gravidarum, is expected to increase further. Therefore, detailed descriptions of the maternal and fetal clinical outcomes of maternal thyrotoxicosis linked to TTTS can be useful for timely diagnosis and management. However, such descriptions are currently lacking in the literature. Case Presentation: We report the case of a 30-year-old woman carrying a monochorionic twin pregnancy complicated by TTTS that induced a relapse of severe hyperemesis gravidarum with overt non-autoimmune hyperthyroidism at 17 weeks of gestation. Following fetoscopic laser coagulation (FLC), both hyperemesis and hyperthyroidism improved within 1 week. Conclusions: The present experience contributes to the knowledge base on maternal thyrotoxicosis linked to TTTS and can be useful in the diagnosis and treatment of future cases; it also emphasizes the need for a high degree of clinical suspicion and for close collaboration between endocrinologists and obstetricians. Another key point is that TTTS-associated hyperemesis gravidarum and maternal hyperthyroidism should be considered in the differential diagnosis of refractory or relapsing hyperemesis gravidarum in women with monochorionic twin pregnancy, because this condition may require more stringent supportive treatment before and during the FLC procedure when the mother is overtly hyperthyroid.