A 23-year-old Hispanic woman, presented to the Emergency Department with periodic bilateral lower extremities flaccid weakness and numbness for 3 months. She reported her symptoms had worsened in severity over the last 2 days and was not able to get up out of bed or chair without assistance. She denied any precipitating trigger factors such as exercise, diet or stress. She also noted 25lb unintentional weight loss in the last 2 months. Of note, patient’s past medical history is significant for Graves’ disease. She was noncompliant with her home medications including iron supplement and methimazole. Physical examination revealed tachycardia, diffusely enlarged thyroid. She also had decreased muscle strength of hip flexion and knee extension (4/5) bilaterally, with diminished patellar reflexes but normal sensation examination. Her serum potassium on admission was low (2.7 mmol/L), free T4 was 4.6 ng/dL and TSH was undetectable. The electrocardiogram showed prominent U waves in V2 and inverted U waves in V3. She was initial managed with propranolol and potassium replacement. Her weakness and tachycardia resolved within 4 hours. Potassium level was increased to 4.9 mmol/l and 4.2 mmol/L in 12 and 24 hours, respectively. Patient was subsequently discharged with adjusted dose of methimazole. She was counselled about medication compliance and referred back to her endocrinologist.
TPP is a rare complication of hyperthyroidism characterized by simultaneous thyrotoxicosis, paralysis and hypokalemia. Early recognition of TPP, potassium replacement, restoration of a euthyroid state and avoidance of precipitating factors is the mainstay treatment. It has been shown that patient with TPP have increased Na-K-ATPase pump number and activity. Insulin and catecholamine can act synergistically with thyroid hormone to increase the pump activity. TPP is more commonly reported in Asian populations. An overall male to female ratio is more than 20:1. It has been suggested susceptible population may have predisposing genetic traits including a mutation in the gene encoding Kir2.6, a potassium channel in skeletal muscle. Na-K-ATPase pump activity is increased by testosterone in animal models, which may explain the predominance of TTP in men. However there are sporadic cases have been reported in Hispanics and females.
Thyrotoxic periodic paralysis (TPP) is the most common cause of acquired periodic paralysis. There are two main biochemical abnormalities, thyrotoxicosis and hypokalemia, which may be precipitated by exercise, high carb diet and stress. It is most common in males of Asian origin. Here, we present a case of TPP in a Hispanic woman, with history of Graves’ disease but noncompliant with her medications.