Endocrine Abstracts

A 32 year old Polish gentleman presented following a collapse with preserved consciousness. Preceding this he was noted to have had a rapid deterioration in mobility with worsening weakness in all four limbs. On further questioning the patient had been diagnosed with hyperthyroidism two months previously and was being treated with propylthiouracil. Positive examination findings included tachycardia with upper limb weakness with 2/5 power bilaterally and lower limbs weakness with 1/5 power. Biochemically, he was found to have a potassium result initially of 3.2 which dropped to 1.8 shortly after treatment with peripheral potassium replacement. His electrocardiogram showed sinus tachycardia and global T wave inversion. His thyroid function tests remained deranged with TSH <0.03 mU/l and T4 of 32.5 pmol/l. He was diagnosed with Thyrotoxic Periodic Paralysis and was admitted to the Intensive Care Unit for close observation and central potassium replacement. His paralysis improved with treatment and he was discharged with close follow up. Thyrotoxic Periodic Paralysis (TPP) is an uncommon acquired presentation in the context of hyperthyroidism, usually manifesting as sudden attacks of painless muscle weakness without loss of consciousness. The pathogenesis is not well understood but it has been postulated thyroid hormone increases tissue responsiveness to beta-adrenergic stimulation, which increases sodium-potassium ATPase activity on skeletal muscle membrane. This drives potassium into cells, leading to hyperpolarisation of the muscle membrane and relative inexcitability of the muscle fibres. As in this case, the acute treatment of TPP is replacement of potassium. A reduction in potassium is often observed after initial replacement therapy and rebound hyperkalaemia, a common problem occurring in those treated for TPP, should be avoided. Ultimately the return to a euthyroid state eliminates further attacks of Thyrotoxic Periodic Paralysis. This uncommon case demonstrates a disabling but readily treated condition essentially being caused by a state of hyperthyroidism.