Severe hypokalemia associated with paralysis after a large carbohydrate intake following exercise

Summary

https://doi.org/10.1093/clinchem/hvad227

Student Discussion

Andrew S. Davison, Lucy Devlin, and Janki Panicker

Case Description

A 22-year-old male Chinese student presented to the department of emergency medicine after he woke up with numbness in the right arm, felt no power in his legs, and was unable to walk or move his legs. He had been to the gym the night before but had only done upper limb work. Following the gym, he had consumed a large carbohydrate load. He was not on any prescribed or over-the-counter medications/supplements and denied using alcohol or recreational drugs.

On examination he was alert and oriented (Glasgow Coma Score 15/15), with pulse 68 beats per minute, blood pressure 110/70 mmHg, oxygen saturation 98%. His chest was clear and abdomen soft. Assessment of his central nervous system revealed that tone and power were intact in the upper limb. In the lower limb, power was 3/5 bilaterally, knee reflexes were absent, and ankle reflexes were positive on reinforcement.

Routine blood tests and arterial blood gas analysis revealed severe hypokalemia in the presence of normomagnesemia, elevated creatine kinase (CK), and lactic acidosis. His electrocardiogram showed a significantly prolonged QTc interval of 577 ms (prolonged QTc defined as >440 ms in men), which was in keeping with the overall biochemical picture.

Following review of the routine biochemistry, the on-call clinical scientist added thyroid function tests to the sample as hyperthyroidism should be considered in the differential diagnosis of hypokalemia in a young Asian male without any obvious cause. Thyroid function tests revealed severe hyperthyroidism. Interestingly, upon clinical assessment, the patient displayed no signs or symptoms of hyperthyroidism including no palpable thyroid nodule; no neck or lymph gland swelling; and no reports of palpitations, weight loss, sweating, or tiredness.