RF23 | PSAT306 Thyrotoxic Periodic Paralysis: An Uncommon Complication Presenting From an Unsuspected Demographic

BACKGROUND: Thyrotoxic Periodic Paralysis (TPP) is a rare complication of thyrotoxicosis mostly reported in Eastern Asian countries with relatively few known cases among non-Asian diaspora in the West. CASE: A 28-year-old African American male with no documented medical history reported to the ED with concern for mechanical fall secondary to progressively worsening muscle weakness. Symptoms began the prior evening with proximal lower extremity and bilateral shoulder weakness which then became severe generalized weakness in all four extremities by morning prompting a fall due to unstable gait and inability to maintain stable seated position. A 60 lb weight loss over the prior year was also noted. Vital signs were notable for blood pressure 154/67 mmHg, tachycardia 109 beats per minute, and tachypnea 20 breaths per minute. Initial labs were significant for hypokalemia 2.2 mEq/L (3.5–5.5 mEq/L), hs-troponin 59 ng/L (n < 20 ng/L), CK 444 U/L (38–174 U/L), ALP 186 U/L (35–110 U/L), TSH < 0.01 uIU/mL (0.35–5.5 uIu/mL), free T4 4.13 ng/dL (0.61–1.12 ng/dL), free T3 15.10 pg/mL (2.5–3.9 pg/mL) and total T3 404 ng/dL (87–178 ng/dL). EKG revealed sinus tachycardia with prolonged PR-interval to 236 ms and prominent precordial U-waves. The patient was given potassium chloride 40 meq IV and PO supplementation, started on propranolol 10mg PO QID and methimazole 30mg PO daily, and admitted to telemetry. Endocrinology recommended increasing the methimazole dose to 20mg PO TID. Thyroid ultrasound revealed a heterogeneous hyper-vascular gland. Follow up labs included: thyroid stimulating immunoglobulin 4.97 IU/L (n < 0.10 IU/L), thyroid peroxidase antibody 19 IU/L (n < 9 IU/mL), gamma glutamyl transpeptidase 22 (9–65 U/L). Findings were consistent with Graves’ disease. Repeat metabolic panel showed appropriate potassium response to supplementation trending between 3.9 meq/L to 4.2 meq/L at six-hour intervals. Hs-troponin peaked at 108 ng/L likely due to demand ischemia in the setting of persistent tachycardia. Follow-up 2D echocardiogram was remarkable for borderline LVH with 60% EF. Patient displayed rapid improvement in muscle strength as potassium normalized; creatine kinase trended down to 49 U/L with resolving myopathy. Patient was discharged on methimazole 20mg PO TID and propranolol 10mg PO QID and told to increase PO intake of potassium rich foods. He was advised to avoid strenuous activity for at least 2 weeks.His potassium was 4.5 meq/L on follow-up endocrinology appointment one week after discharge. He did not endorse residual symptoms and remained compliant with medications. CONCLUSION: This is a case of TPP amidst undiagnosed Graves’ disease that resolved with timely potassium repletion. Documented TPP cases in non-Asians, especially African Americans, are rare and should be investigated further. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m., Sunday, June 12, 2022 1:12 p.m. - 1:17 p.m.