Rhabdomyolysis due to hypothyroidism without any precipitating factor

Case report

A 27-year-old man was brought in as an emergency in respiratory distress. He was bradycardic with a pulse of 42 bpm and hypotensive with a systolic blood pressure of 60 mmHg.

He had a history of muscle cramps and anuria of one day’s duration. There was no other co-morbidity. He had performed no unaccustomed work nor exercise. He had not used any medication.

Examination revealed dry skin, coarse facial features and absent ankle reflexes. Laboratory analysis revealed: serum creatinine = 362.4 µmol/L; serum potassium = 7.2 mmol/L; serum calcium = 1.67 mmol/L; thyroid-stimulating hormone = 436 mIU/L; triiodothyronine = 0.3 ng/mL; thyroxine = 1.06 µg/dL; and serum creatinine phosphokinase = 33,354 IU/L.

An abdominal ultrasound measured the right kidney as 10 × 5.2 cm and the left as 10.5 × 5 cm.

Mechanical ventilation was introduced, while the electrocardiogram showed tall T waves and absent P waves. Haemodialysis was commenced and a temporary pacemaker wire inserted. L-thyroxine supplementation at an initial dose of 25 µg daily was commenced.

He reverted to normocardia after 72 h. Several sessions of haemodialysis were required before his urine output normalized. L-thyroxine was increased weekly to 150 µg daily. Informed consent was obtained from the patient.

Discussion

Hypothyroidism can be a cause of rhabdomyolysis. Myolysis in hypothyroidism is caused by changes in muscle fibres from fast-twitching type II to slow-twitching type I fibres, a deposition of glycosaminoglycan, poor contractility of actin-myosin units, resulting in low myosin ATPase activity, and low ATP turnover in the skeletal muscles. ¹ With hypothyroidism, there is an inhibition of mitochondrial activity in muscle cells as well as dysregulation of many metabolic pathways such as the Krebs cycle, fatty acid catabolism and glycolytic energy production. ² These metabolic abnormalities may provoke hypothyroid patients to develop rhabdomyolysis.

Reported precipitating factors included the use of lipid-lowering drugs ³ or strenuous exercise. ⁴ Rhabdomyolysis may also develop owing to hypothyroidism alone without such precipitating factors. ⁵ In all five cases,^5–7 rhabdomyolysis and hypothyroidism were diagnosed for the first time simultaneously. All five patients had thyroid-stimulating hormone levels >100 mIU/L. Their serum creatinine was in the range of 79.5–167.8 µmol/L.^5–7