ODP390 Metastatic Gestational Trophoblastic Neoplasia Masquerading as Thyroid Storm in a Girl with Molar Pregnancy and Hyperthyroidism

: The Case Patient is a 16-year-old female with molar pregnancy, admitted for D&C, referred for hyperthyroidism, concern for thyroid storm. A month prior, she presented with heavy vaginal bleeding, morning sickness. Ultrasound showed blighted ovum. HCG was significantly elevated, 668,123 mIU/mL. TSH was low at 0. 01 mIU/L, Free T4 elevated 2.3 ng/dL. No family history of thyroid dysfunction. She was for was noted to have respiratory distress, hypoxia, and tachycardia in the 120s post-operatively. LFTs normal, no fever, jaundice or CNS manifestations. Chest CT showed bilateral lower lobe localized pulmonary edema concerning for trophoblastic fluid embolism vs thyroid storm. BWPS = 40. She was placed on PTU, beta blockade, Lugol's iodine, and hydrocortisone. Repeat chest CT showed diffuse pulmonary nodules consistent with gestational trophoblastic neoplasm (GTN). No other metastasis on further imaging (chest, abdomen, pelvis, brain). Clinical status improved, FT4 normalized 5 days after starting treatment. TRAbs negative. She was discharged on Methimazole and Atenolol, which were eventually discontinued. HCG levels significantly decreased after D&C but remained detectable on follow-up. Endocervix/uterine curettage showed intraplacental choriocarcinoma arising within a complete hydatidiform mole. She is followed by Oncology and currently undergoing chemotherapy. DISCUSSION: HCG-mediated hyperthyroidism include gestational transient thyrotoxicosis, hyperemesis gravidarum, and trophoblastic hyperthyroidism (TH). Due to significant homology between TSH and the beta-subunit of HCG, HCG can cause hyperthyroidism. 2-60% of women with trophoblastic disease may have symptomatic hyperthyroidism at time of diagnosis which can be severe. Patients with GTN (choriocarcinoma in our case) have a higher likelihood of TH, as HCG exceeds 100,000 mIU/mL. Choriocarcinoma is the most aggressive type of GTN characterized by vascular invasion and widespread metastases, of which the most common sites are vagina and lungs. Patients with pulmonary metastasis my present with respiratory distress, chest pain, cough or hemoptysis. Our patient was initially thought to have impending thyroid storm mainly from findings of pulmonary edema, respiratory distress, tachycardia, and precipitant history (D&C), and was managed as such while further workup was being undertaken. Realization that the initial chest CT findings of pulmonary edema were actually related to multiple pulmonary nodules and GTN made thyroid storm less likely. Hyperthyroidism typically resolves with decreasing HCG levels in TH. Indeed, our patient no longer needed ATD once her HCG levels subsided s/p D&C. CONCLUSION: One of the most common sites of metastasis in GTN is the lungs. An acute presentation of respiratory distress and pulmonary findings on chest imaging upon simultaneous discovery of TH may complicate management as thyroid storm needs to be considered. Although a higher index of suspicion for metastatic GTN should be made in this situation, a conservative management approach of treating for possible impending thyroid storm until definitive diagnosis has been established is prudent. Presentation: No date and time listed