FRI570 Repatha Induced Thyroid Storm

Disclosure: L.R. Sepulveda-Garcia: None. L.N. Madera Marin: None. L. El Musa Penna: None. W. Medina-Torres: None. M.A. Ortiz-Rivera: None. A. Rosado-Burgos: None. M. Alvarado: None. M. Ramirez: None. L.A. Gonzalez-Rodriguez: None. Introduction: Proprotein convertase subtilisin kexin type 9 (PCSK9) inhibitors are an effective medical therapy for lowering plasma LDL-cholesterol and enhancing the LDL-cholesterol ability of statins. In 2020, a case of transient hyperthyroidism secondary to evolocumab was reported. We present a case of impending thyroid storm after a patient received evolocumab. Patient description: 60 y/o female patient with medical history remarkable for hyperlipidemia, anti-TPO positive non-toxic multinodular goiter, hypertension, fibromyalgia, and coronary artery disease who presented with heat intolerance, palpitations, tremors, and insomnia after second dose of evolocumab. At physical exam found with tachycardia, hypertension, anxious mood, tremors, leg pitting edema +1 bilateral, and deep tendon reflexes +3 in lower extremities, although no palpable or painful goiter. Laboratories compatible with hyperthyroidism [TSH < 0.008 uIU/mL (0.3 – 3.0 uIU/mL), Free T4 4.29 ng/dL (0.89 – 1.76 ng/dL), Total T4 20.03 ug/dL (4.5-12 ug/dL)] and clinically with severe thyrotoxicosis. Patient was sent to ED for further evaluation and management. Case outcomes: Upon admission patient presented with a tonic-clonic seizure with short post ictal state. Burch-Wartofsky scale Point Scale 35, consistent with impending thyroid storm. Thyrotoxicosis management given requiring high doses of PTU, hydrocortisone and propranolol, including the need to add cholestyramine to the regime. By day 9 of therapy, patient was transitioned to methimazole 30mg daily with discontinuation of hydrocortisone and cholestyramine. Upon discharge, 2 weeks later, thyroid function tests had normalized to a FT4 of 1.39 ng/dL and a Total T4 of 9.6 ug/dL. Case discussion: A case of transient hyperthyroidism with PCSK9 inhibitor was previously reported requiring only symptomatic treatment. In this case a patient presented with severe thyrotoxicosis after she received her second dose of evolocumab. PCSK9 inhibitor therapy immunological influence on thyroid remains unknown. This case shows the importance of thyroid function test follow up in patients on PCSK9 inhibitor therapy and the possibility of immunological influence on the thyroid. Presentation: Friday, June 16, 2023