Clinical review: Thyrotoxic periodic paralysis: a diagnostic challenge.
BACKGROUND
The aim of this article was to review the clinical presentation, pathogenesis, and management of thyrotoxic periodic paralysis (TPP).


METHODS
A MEDLINE search was conducted for articles published during the last 40 yr based on the key words thyrotoxic periodic paralysis and hypokalemic periodic paralysis. A total of 281 primary articles and 168 references of the retrieved articles were also reviewed.


RESULTS
TPP is a common complication of hyperthyroidism in Asian men but is increasingly seen in Western countries. Hypokalemia and muscle paralysis results from a sudden intracellular shift of potassium and is not due to potassium deficiency. Clinical features of hyperthyroidism in patients with TPP may be subtle. Immediate potassium supplementation prevents serious cardiopulmonary complications and may hasten the recovery of muscle weakness. Nonselective beta-adrenergic blockers can ameliorate and prevent recurrence of the paralytic attacks. This episodic paralysis will remit with definitive control of hyperthyroidism. Increased sodium-potassium ATPase pump activity and enhanced insulin response in patients with TPP is postulated to contribute to the hypokalemia. The genetic predisposition for TPP is not entirely clear. Association of polymorphisms of the calcium channel alpha1-subunit gene with TPP has been noted.


CONCLUSIONS
Due to population mobility, TPP is increasingly common in Western countries. Early diagnosis and prompt treatment prevent life-threatening complications associated with hypokalemia and muscle weakness. Assaying of thyroid function in patients with hypokalemic paralysis distinguishes TPP from other forms of hypokalemic periodic paralysis.
Kung
Annie W C
AW
Department of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong, China. awckung@hkucc.hku.hk
D013956:Antithyroid Agents / Q000627:therapeutic use; D001208:Asia; D004576:Electromyography; D015444:Exercise; D006111:Graves Disease / Q000150:complications / Q000175:diagnosis / Q000628:therapy; D006801:Humans; D006980:Hyperthyroidism / Q000150:complications; D007008:Hypokalemia / Q000150:complications / Q000188:drug therapy; D020514:Hypokalemic Periodic Paralysis; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D016239:MEDLINE; D008297:Male; D018482:Muscle, Skeletal / Q000503:physiopathology; D009135:Muscular Diseases / Q000175:diagnosis* / Q000209:etiology* / Q000628:therapy; D010243:Paralysis / Q000175:diagnosis* / Q000209:etiology* / Q000628:therapy; D010507:Periodicity; D011188:Potassium / Q000378:metabolism; D011189:Potassium Chloride / Q000008:administration & dosage; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013963:Thyroid Hormones / Q000502:physiology; D013965:Thyroidectomy; D013971:Thyrotoxicosis / Q000150:complications* / Q000175:diagnosis* / Q000628:therapy
D013956:Antithyroid Agents; D007457:Iodine Radioisotopes; D013963:Thyroid Hormones; D011189:Potassium Chloride; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium