MON-639 Management of Differentiated Thyroid Cancer With Co-Existing Human Chorionic Gonadotropin (hCG) Producing Tumor

Abstract L.S. Azeez: None. K.D. Thallapureddy: None. E.G. Sherry: None. S. Raghunathan: None. Human Chorionic Gonadotropin (hCG)-producing tumors cause an elevation in thyroglobulin levels resulting in a suppression of TSH; this complicates screening and management following surgical treatment for differentiated thyroid cancer. This is a case of a patient with a history of disseminated hCG-producing germ cell tumor, presenting with detectable thyroglobulin levels after total thyroidectomy for Papillary Thyroid Cancer (PTC). Patient is a 25-year-old male with history of mixed germ cell tumor of the testes with hepatic and pulmonary metastases and intracranial recurrence treated with chemotherapy and radiation therapy. Medical history also includes chronic kidney disease (CKD) stage II. Initial β-hCG level on diagnosis of malignancy measured > 200,000 mIU/mL (0-2 mIU/mL); serial monitoring post-treatment showed normalization of levels. Follow-up imaging in 4 years showed incidental right thyroid nodule. Thyroid ultrasound showed a right lobe thyroid nodule measuring 0.8 x 0.7 x 0.9 cm, round and solid with posterior acoustic shadowing and internal flow on Doppler. Fine Needle Aspiration (FNA) was done given patient history and revealed benign cytology. Repeat thyroid ultrasound performed 1 year later re-demonstrated the hypoechoic nodule in the mid-pole of the right thyroid lobe, with increased size, irregular margins and peripheral rim calcification. Repeat biopsy showed suspicion for malignancy (Bethesda V). Pathology from total thyroidectomy revealed focal 0.9 cm conventional type PTC, with low risk of recurrence and no extrathyroidal extension (PT1a); lymph nodes were not evaluated. The patient was started on levothyroxine 112 mcg daily. Labs in 4 months showed a TSH of 0.04 uIU/mL (0.52- 4.13 uIU/mL), Free T4 1.8 ng/dL (0.8-1.3 ng/dL) and thyroglobulin measuring at 7.4 ng/mL (< 0.1 ng/mL). Thyroglobulin measurements three and then five months later revealed an upward trend. Given detectable thyroglobulin levels and history of metastatic germ cell tumor of the testes, the decision was ultimately made to treat with radioactive iodine therapy (RAI). The patient was given 30 mCi of I-131 given history of CKD. A post-therapy scan showed focal uptake in the central neck and physiological renal/bladder uptake. During this period, β-hCG levels remained undetectable. The patient continues to be monitored for recurrence of germ cell tumor of the testes. Patients with PTC and co-existing hCG-producing germ cell tumors have an increased risk of PTC recurrence given stimulation of thyroglobulin production by hCG. Management of hCG-producing tumors, therefore, becomes vital to prevent the recurrence of PTC. Any increase in thyroglobulin levels should be interpreted in relation to the hCG levels. These patients are at a higher risk of recurrence and may benefit from RAI therapy, even if determined to have a low risk of PTC recurrence per ATA guidelines. Monday, June 3, 2024