THU230 Consumptive Hypothyroidism Secondary To Hemangioma

Disclosure: R. Thirunagari: None. D. Taha: None. Background: Peripheral Hypothyroidism also known as consumptive hypothyroidism has been rarely described in association with vascular tumors such as hemangiomas. It is due to excessive production of type 3 iodothyronine deiodinase (D3) enzyme by the hemangioma leading to increased rate of deiodination of T4 and T3 to inactive forms. Clinical case: We report a 4-year-old girl who was diagnosed with consumptive hypothyroidism at the age of 2 months. She was born at full term via scheduled C-section. Mother has hypothyroidism. She was admitted to NICU for respiratory distress and needed oxygen supplementation. She had a large hemangioma covering most of her back on exam. An ultrasound of the head/neck soft tissue showed an ill-defined lobular heterogeneous mass measuring 3.4 x 1.2 x 4.5 cm, markedly hypervascular with both arterial and venous flow likely consistent with hemangioma. At follow up plastic surgery clinic she had respiratory distress which necessitated readmission to the NICU for further workup and possible initiation of Propranolol. An abdominal ultrasound showed enlargement of the right adrenal and on further dedicated ultrasound a right suprarenal lobulated mass as well as intrathoracic soft tissue mass were found. MRI of the abdomen and thorax, revealed multiple large bilateral paraspinal masses throughout the thoracic and lower cervical spine(largest measuring 3.3 x 7 x 15 cm AP) invading the neural foramen at multiple levels, and causing mass effect on the spinal cord which is displaced to the left. There was mass effect on adjacent vascular structures without significant vascular compromise. Biopsy was consistent with hemangioma. Thyroid Newborn screening result was normal. Thyroid evaluation done at 3 months age revealed, free T4 level of 1.04 ng/dL and TSH level of 11.3 µIU/mL. She was started on Levothyroxine 50 mcg daily. Reverse T3 was elevated at 139.2 ng/dl (reference range 13-107 ng/dl) 2 weeks after treatment initiation. She was initiated on propranolol and was followed up by plastic surgery and oncology. She had a very good response to Propranolol. Follow up MRI at 4 years shows almost complete resolution of the mass. She continues to be on Levothyroxine but is requiring smaller dose. Conclusion: Infantile hemangiomas can express high levels of type 3 iodothyronine deiodinase (D3), an enzyme that catalyzes the inner-ring deiodination of T4 to reverse T3 (rT3) and of T3 to 3,3'-diiiodothyronine (T2), both of which are biologically inactive. The hypothyroidism is a result of degeneration of thyroid hormones at rates that exceed the synthetic capacity of the infant's thyroid gland. Our case illustrates the importance of closely monitoring thyroid function tests in infants with large hemangiomas even if newborn thyroid screening result is normal. Some infants may require higher Levothyroxine doses than usual. Hypothyroidism usually resolves after resolution of the mass. Presentation: Thursday, June 15, 2023