Endocrine Abstracts

Thyrotoxic Periodic Paralysis (TPP) is a rare channelopathy associated with hyperthyrodism causing potentially fatal complications of hypokalemia due to a massive intracellular potassium shift and severe muscle paralysis. TPP is rare in non-Asians, however with population migration increasingly seen in Western countries. The diagnosis is often delayed due to the subtleness of underlying thyrotoxicosis and the similarities of the paralysis with familial hypokalaemic periodic paralysis (FHPP). The channelopathy is of genetic/acquired in nature affecting sodium and potassium ion channels across cell membranes including KCNJ family and L-type calcium channel. A 24-year old, White European lady presented with tetraparesis and profound hypokalemic. These paralytic episodes were recurrent for previous 6 years, occuring once/twice per year. Only few weeks prior, she was diagnosised with Graves’ thyrotoxicosis (free thyroxine (FT4) 43.7 (12-22 pmol/l), free triiodothyronine (FT3) 24.6 (2.0-7.0 pmol/l), thyroid stimulating hormone (TSH) <0.02 mIU/L (0.4-4.5 mIU/l)), positive thyrotropin receptor antibodies) and commenced on carbimazole. Her father had hypokalemic periodic paralysis, but the details were unknown. Biochemstry at presentation revealed, low potassium 1.6mmol/l, raised FT4 27.1 pmol/l and FT3 11.6 pmol/l, and supprsed TSH of <0.02 mIU/l. She was treated with IV potassium and higher doses of carbimazole with full recovery from the episode. Her genetic analysis are awaited. TPP can be confused with FHPP. TPP is a sporadic disease seen mainly in Asian males, and the familial trait is rare while the FHPP is an autosomal dominant condition mainly affecting Caucasians. Additionally, there may be an overlap of genetic predisposition between FHPP and TPP. Although, our patient had paralytic episodes prior to Graves’ thyrotoxicosis, this episode was severe; her underlying diagnosis of TPP vs. FHPP is unclear pending gentics analysis. We highlight a rare case of hypokalemic periodic paralysis and complexities incurred in its diagnosis and management.