Some acute TM patients may present symptoms of blurred vision and bulging eyes due to eye muscle degradation and inflammation, but documented cases are rare. Acute TM patients usually have very weak respiratory muscles and often severe respiratory failure occurs. Cause
TM is directly related to thyroxine toxicity. It is believed this disorder is a direct result of hyperthyroidism, specifically hyperthyroidism caused by Graves disease or a multinodular goiter. Both cause the thyroid gland to overproduce thyroxine. A multinodular goiter is a condition where the thyroid develops nodules. Overproduction of thyroxine is due to the enlargement of the thyroid gland. Graves disease is an autoimmune condition where the immune system chronically stimulates the TSH receptor in the thyroid and induces overproduction of the thyroxine hormone. Pathophysiology
Excess thyroxine is believed to bring about the onset of thyrotoxic myopathy and eventually cause the degradation of muscle tissue. Thyroxine is a hormone produced in the thyroid gland that regulates the growth metabolism of the nervous system and regulates basal metabolic rate of many cell types. Scientists agree thyroxine brings about the degradation of muscle fibers specifically at the motor end plates of neuromuscular junctions. There is debate as to whether thyroxine degrades the motor end plates from the muscular side, from the nervous system side, or a combination.To understand how high levels of thyroxine can be toxic and lead to thyrotoxic myopathy physiologically, consider basic neuromuscular junction function.
Depending on the severity of the TM progression symptoms may take up to a year to completely reverse the damage done by TM. Untreated TM can eventually cause severe respiratory distress or arrest possible leading to death, yet this is very rarely seen. Epidemiology
The onset of TM requires toxic levels of the thyroxine hormone due to overproduction by the thyroid gland. Documented cases have only been diagnosed in conjunction with patients with hyperthyroidism. While hyperthyroidism is more common in women, the development of TM was more common among men with hyperthyroidism. Case studies of patients with diagnosed hyperthyroidism showed that only about half of them complained of symptoms characteristic of TM. Further examination as described above indicated that about 75% of the studied patients showed signs of muscle fiber degeneration. This indicates that either at the time of study some patients were in early stages of TM or the symptoms were insignificant patients. References


== External links ==