A 37‐year‐old woman presented with complaint of 2 days of severe generalized muscle weakness. The weakness was described as more proximal rather than distal. She reported associated palpitations, diarrhea, and heat intolerance. She denied any weight loss, paresthesias, numbness, tingling, difficulty finding words, or dysphagia. She had a heart rate of 117 beats per minute; bilateral lid retraction with mild lid lag and no definite exophthalmus; a diffusely enlarged, nontender thyroid that moved well with swallow; no thyroid bruits; and no cervical lymphadenopathy. She also had 3/5 muscle strength diffusely, brisk deep tendon reflexes, and a mild tremor. Laboratory data were consistent with thyrotoxicosis with an undetectable thyroid‐stimulating hormone (TSH) level and free T4 level of 3.5 ng/dL Her serum potassium was 1.9 mmol/L She had a non–anion gap metabolic acidosis with a bicarbonate level of 14 mmol/L creatine kinase was 276 units/L thyroid‐stimulating immunoglobulin titer was 313%. EKG revealed sinus tachycardia, a right bundle branch block, and a QTc of 550 ms. She was diagnosed with thyrotoxic periodic paralysis. She was treated as an inpatient with aggressive oral and intravenous potassium repletion, methimazole, and beta‐blockade. She improved symptomatically, and was discharged home on methimazole and oral potassium repletion.
Generalized weakness is a common admitting diagnosis encountered by the hospitalist. Initial workup often includes assessment of thyroid function. Although thyrotoxic periodic paralysis is relatively uncommon, if left untreated it can lead to complications of ventricular arrhythmia and respiratory failure. Hypokalemia results from the massive shift of potassium into the cells rather than net potassium loss from the body. Symptoms range from mild muscle weakness to complete flaccid paralysis, and proximal muscles are usually affected more than distal. Sensation remains intact in these patients, and bowel and bladder function is not affected. Treatment of the hyperthyroidism results in resolution of the periodic attacks, as the hypokalemia resolves when the patient is clinically and biochemically euthyroid. Early recognition and treatment of thyrotoxic periodic paralysis can prevent life‐threatening complications of this disease.
Although thyrotoxic periodic paralysis is a relatively uncommon metabolic cause of acute muscle weakness and hypokalemia, it can result in profound generalized weakness, ventricular arrhythmias, and respiratory failure. This condition should remain on the differential diagnosis of generalized weakness in the hospitalized patient.
To cite this abstract:Brooks M. A Weak Diagnosis: Thyrotoxicosis with a Twist. Abstract published at Hospital Medicine 2013, May 16-19, National Harbor, Md. Abstract 468. Journal of Hospital Medicine. 2013; 8 (suppl 2). https://www.shmabstracts.com/abstract/a-weak-diagnosis-thyrotoxicosis-with-a-twist/. Accessed November 12, 2019.