An unusual cause of hypokalaemia

A man in his 50s was admitted to the endocrinology ward for persistently low potassium levels. One year previously, he had been admitted under the neurology department with a two year history of recurrent limb weakness. He had no known medical conditions or history of long term drug use. Physical examination revealed stable vital signs, no abnormalities on auscultation of the heart and lungs, grade 4 muscle strength in both lower extremities, and decreased tendon reflexes and muscle tone. Blood tests performed one year previously had indicated hypokalaemia, hypomagnesaemia, and hyperthyroidism (table 1), and he had received a diagnosis of hypokalaemic periodic paralysis and hyperthyroidism. The hyperthyroidism had improved after one year of treatment with iodine radiation therapy; however, his potassium level had remained low, and simultaneous oral and intravenous potassium supplementation had been ineffective. Results of tests conducted …