Choriocarcinoma Induced Thyrotoxicosis in a Male Adult

Introduction: Germ cell tumors normally occur in the gonads but may be found in extragonadal sites (due to abnormal migration of germ cells during embryogenesis). Metastatic choriocarcionomas are non-seminomatous germ cell tumors which overproduce beta Human Chorionic Gonadotropin (hCG). Rarely, thyrotoxicosis can be driven by germ cell tumor-mediated hCG excess. This hormone binds to the TSH receptor with reduced potency compared to intact TSH. Paraneoplastic thyrotoxicosis, driven by extremely high levels of hCG, is a rare condition which can be associated with choriocarcinomas. Case Presentation: We present a case of 29-year-old man with metastatic extragonadal choriocarcinoma under active treatment with oxaliplatin, paclitaxel, gemcitabine (2 cycles completed), right upper lobe resection and whole brain radiation. He was admitted for small bowel obstruction and persistent tachycardia which prompted evaluation of thyroid function. His initial labs were remarkable for TSH <0.01 mclU/mL (0.27-4.20 mclU/mL), FT4 of 6.38 ng/dL (0.93-1.70 ng/dL), total T3 261 ng/dL (75-170 ng/dL), and beta hCG 578,259 mlU/ML (0-2 mlU/ML). His most recent round of chemotherapy was 7 days prior to admission. He was started on atenolol and methimazole but his FT4 rapidly declined, hence methimazole was stopped after one dose of 40 mg. Sevenfold decrease in FT4 to 0.93 ng/dL correlated with fivefold decrease in beta hCG levels to 98,921 mlU/ML. A week later his FT4 increased to 2.42 ng/dL along with increase of beta hCG to 448,116 mlU/ML. At this point he developed multiple complications due to progressive metastatic disease including acute urinary retention, shortness of breath, abdominal pain, tachycardia, acute anemia and thrombocytopenia, anxiety and was started on methimazole as part of palliative treatment for symptom relief. Unfortunately, he passed away three weeks after initial presentation of thyrotoxicosis due to widespread disease. Discussion: Choriocarcinoma is very rare and aggressive germ cell tumor especially in males. Unfortunately, the widespread nature of choriocarcinomas at the time of diagnosis is a major main reason for poor prognosis. Clinical manifestations of thyrotoxicosis associated with choriocarcinoma such as tachycardia, anxiety, tachypnea are variable and often can overlap with constitutive symptoms in widespread malignancy. Even if a definitive cure of choriocarcinoma is not attainable, recognizing an associated paraneoplastic thyrotoxicosis can provide an important pathway to provide palliative symptom relief.