Subsequent attacks may be prevented by avoiding known precipitants, such as high salt or carbohydrate intake, until the thyroid disease has been adequately treated.Treatment of the thyroid disease usually leads to resolution of the paralytic attacks. Depending on the nature of the disease, the treatment may consist of thyrostatics (drugs that reduce production of thyroid hormone), radioiodine, or occasionally thyroid surgery. Epidemiology
TPP occurs predominantly in males of Chinese, Japanese, Vietnamese, Filipino, and Korean descent, as well as Thais, with much lower rates in people of other ethnicities. In Chinese and Japanese people with hyperthyroidism, 1.8–1.9% experience TPP. This is in contrast to North America, where studies report a rate of 0.1–0.2%. Native Americans, who share a genetic background with East Asians, are at an increased risk.The typical age of onset is 20–40. It is unknown why males are predominantly affected, with rates in males being 17- to 70-fold those in females, despite thyroid overactivity being much more common in women. History
After several case reports in the 18th and 19th centuries, periodic paralysis was first described in full by the German neurologist Carl Friedrich Otto Westphal (1833–1890) in 1885. In 1926 the Japanese physician Tetsushiro Shinosaki, from Fukuoka, observed the high rate of thyroid disease in Japanese people with periodic paralysis. The first English-language report, in 1931, originated from Dunlap and Kepler, physicians at the Mayo Clinic; they described the condition in a patient with features of Graves disease. In 1937 periodic paralysis was linked with hypokalemia, as well as precipitation of attacks with glucose and insulin.
Thyrotoxic periodic paralysis (TPP) is a condition featuring attacks of muscle weakness in the presence of hyperthyroidism (overactivity of the thyroid gland). Hypokalemia (a decreased potassium level in the blood) is usually present during attacks. The condition may be life-threatening if weakness of the breathing muscles leads to respiratory failure, or if the low potassium levels lead to cardiac arrhythmias (irregularities in the heart rate). If untreated, it is typically recurrent in nature.The condition has been linked with genetic mutations in genes that code for certain ion channels that transport electrolytes (sodium and potassium) across cell membranes. The main ones are the L-type calcium channel α1-subunit and potassium inward rectifier 2.6; it is therefore classified as a channelopathy. The abnormality in the channel is thought to lead to shifts of potassium into cells, under conditions of high thyroxine (thyroid hormone) levels, usually with an additional precipitant. Treatment of the hypokalemia, followed by correction of the hyperthyroidism, leads to complete resolution of the attacks. It occurs predominantly in males of Chinese, Japanese, Vietnamese, Filipino, and Korean descent. TPP is one of several conditions that can cause periodic paralysis. Signs and symptoms
An attack often begins with muscle pain, cramping, and stiffness. This is followed by weakness or paralysis that tends to develop rapidly, usually in late evening or the early hours of the morning. The weakness is usually symmetrical; the limb muscles closer to the trunk (proximal) are predominantly affected, and weakness tends to start in the legs and spread to the arms.