7668 Rhabdomyolysis Associated with Severe Hypothyroidism

Abstract Disclosure: H. Soe: None. P. Mikkilineni: None. Background: Over 70% of the patients with newly diagnosed hypothyroidism can present with muscle complaints such as weakness, fatigability, cramps, myalgia. However, rhabdomyolysis, which is the rapid breakdown of skeletal muscle cells, is the rare presentation. Clinical Case: A 70-year old male patient with history of rheumatoid arthritis, hyperlipidemia, prior CVA (left hemispheric subcortical stroke) 6 months ago without residual deficit presented to the hospital with poor oral intake and generalized muscle weakness for 3 weeks. He was unable to get out of bed without assistance and also needed adult diapers. Found to have new-onset severe hypothyroidism with TSH 228 uIU/ml (Ref: 0.350-4.940) and FT4 <0.40 ng/dL (Ref: 0.70-1.50), positive TPO antibody 197 IU/ml (Ref: 0-34). No prior thyroid labs were available and no known history of thyroid disorder was recorded. He has never been on Amiodarone or Lithium before. On physical exam, he was alert and oriented. There was no goiter or palpable thyroid nodule. There was no focal neurological deficit and no peripheral edema. There were no other signs and symptoms pertinent to hypothyroidism except mild bradycardia (HR 56-60) and borderline low blood pressure. AM cortisol was 10.1 ug/dL (Ref: 3.7-19.4). EKG showed low-voltage sinus bradycardia. Echocardiogram was normal. Urinalysis was positive for large blood but only 3 RBCs were present which raised the suspicion of rhabdomyolysis. Creatinine kinase (CK) was 15,584 IU/L (Ref: 30-200). Other laboratory studies were significant for acute renal failure with mild hyperkalemia and mild hypocalcemia, also transaminitis; BUN 130 mg/dl (Ref: 8-26), Creatinine 9.51 mg/dl (Ref: 0.72-1.25), eGFR 5 ml/min/1.73 m2 (Ref: >59), AST 435 IU/L (Ref: 5-34), ALT 269 IU/L (Ref: <55), ALP 171 IU/L (Ref: 40-150). On medication review, he was started on Atorvastatin 80 mg daily during prior admission for CVA 6 months ago. He received IV fluids, s/p 1 dose of Hydrocortisone 100 mg IV, Levothyroxine IV 200 mcg, followed by Levothyroxine IV 50 mcg daily x 3 days and switched to Levothyroxine PO 100 mcg daily (weight-based dose). Atorvastatin was on hold. He became anuric during the hospital course and received 2-3 sessions of hemodialysis. 3-4 days later, CK was trending down to 3000 IU/L, FT4 improved to 0.54 ng/dl and there was also significant improvement in kidney and liver functions. The patient was diagnosed with acute renal failure secondary to rhabdomyolysis associated with severe hypothyroidism caused by Hashimoto's thyroiditis, in the setting of high dose statin use. Conclusion: Clinicians should raise the suspicion of rhabdomyolysis in a patient with severe hypothyroidism, especially in patients with recent high dose statin use as rhabdomyolysis can be a rare and fatal complication of severe hypothyroidism, in the presence of precipitating factors. Presentation: 6/2/2024