Thyrotoxic Myopathy (TM) is a neuromuscular disorder that develops due to the overproduction of the thyroid hormone thyroxine. Also known as hyperthyroid myopathy, TM is one of many myopathies that lead to muscle weakness and muscle tissue breakdown. Evidence indicates the onset of TM may be caused by hyperthyroidism (Kazakov, 1992). There are currently two known causes of hyperthyroidism that lead to development of TM including a multinodular goiter and Graves disease. Physical symptoms of TM may include muscle weakness, the breakdown of muscle tissue, fatigue, and heat intolerance (Quin, 1951).Physical acts such as lifting objects and climbing stairs may become increasingly difficult (Horak, 2000). If untreated TM can be an extremely debilitating disorder that can, in extreme rare cases, lead to death. If diagnosed and treated properly the effects of TM can be controlled and in most cases reversed leaving no lasting effects.
Physical Symptoms may include:
• Muscle Weakness
• Degeneration of Muscle Tissue
• Fatigue
• Heat Intolerance
Chronic TM - Symptoms of chronic TM arise slowly overtime. Patients usually complain of decreased exercise tolerance, increased fatigue, and difficulty completing certain tasks after six months of TM onset (Kazakov, 1991; Quinn, 1951). If chronic TM goes untreated worse symptoms may develop including difficulty swallowing and respiratory distress. These occurrences are rare since diagnosis of chronic TM usually occurs during the early stages of onset prior to these symptoms development.
Acute TM - Acute TM is more rare than chronic TM and unlike chronic TM symptoms appear within days of TM onset. Acute TM degrades muscle fibers rapidly. Due to the rapid degradation of muscle fibers patients usually complain of severe muscle cramps and muscle pain. Some acute TM patients may also 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 ( Lichtstein, 2006).
