D2I2.
endocrine

Thyrotoxic periodic paralysis

Thyrotoxic periodic (TPP) is a rare condition featuring attacks of muscle weakness in the presence of hyperthyroidism. Hypokalemia is usually present during attacks. The condition may be life-threatening if weakness of the breathing muscles leads to failure, or if the low levels lead to abnormal heart rhythms. If untreated, it is typically recurrent in nature.

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Plain-language summary adapted from Wikipedia. Not medical advice.