Overview of hyperthyroid myopathy
Hyperthyroid myopathy is one of the complications of hyperthyroidism, which is clinically classified into acute hyperthyroid myopathy, chronic hyperthyroid myopathy, hyperthyroid periodic paralysis (TPP), hyperthyroid myasthenia gravis, and infiltrative proptosis with ophthalmic paralysis according to the characteristics of the onset of the disease and the location of the lesions involved. Of these, chronic hyperthyroid myopathy and hyperthyroid periodic paralysis (TPP) are more common. Chronic hyperthyroid myopathy is one of the more common clinical types of hyperthyroid myopathy, with a slow onset of disease. Due to the lack of specific symptoms and signs, it is often masked by the symptoms of weakness and lethargy inherent in hyperthyroidism, and is easily underdiagnosed in the clinic.
Etiology
The cause of chronic hyperthyroid myopathy has not been fully clarified.
Symptoms
1. Acute hyperthyroid myopathy
Acute hyperthyroid myopathy or acute hyperthyroid encephalopathy, also known as “hyperthyroidism with acute medullary palsy”, is relatively rare. It may be due to the elevation of thyroid hormones, especially free thyroid hormones, in the blood circulation, which aggravates the symptoms of hyperthyroidism and leads to cerebral symptoms, and medullary palsy; or in the state of stress, the activity of sympathetic nervous system enhances, and releases a large amount of catecholamines, and thyroid hormones may enhance the catecholamines, and the catecholamines may enhance the catecholamines. In addition, thyroid hormone can enhance the effect of catecholamines, so that the tissue reactivity increases and leads to crisis.
2. Chronic hyperthyroid myopathy
Chronic hyperthyroid myopathy is one of the more common hyperthyroid myopathies, which occurs more often in middle-aged men and less often in women, with a slow progression of the disease. Chronic hyperthyroid myopathy is mainly characterized by degenerative changes in muscle fibers, and a large number of lymphocytes and plasma cells infiltration.
The main manifestations are gradually aggravated muscle weakness, wasting and even muscle atrophy, but there is no muscle paralysis and sensory impairment. The course and severity of hyperthyroidism is related to the occurrence of chronic myopathy, but not parallel to the degree of muscle weakness. Generally, after hyperthyroidism is controlled, muscle weakness and muscle atrophy can be improved.
3. Hyperthyroidism periodic paralysis (TPP)
The main clinical manifestation is episodic muscle weakness, flaccid paralysis, bilateral symmetry, with the lower limb muscle involvement is common, rarely involved in the muscles above the neck, such as causing paralysis of intercostal muscles and diaphragm, can be presented with respiratory distress, and in serious cases, life-threatening. Seizures are more frequent at night, lasting from a few hours to 2-3 days, and the frequency of seizures can be several times a day or once in several years. Seizures are characterized by decreased muscle tone and diminished or absent tendon reflexes, but are not accompanied by sensory abnormalities. Blood potassium is decreased, electrocardiogram may have hypokalemic changes, urine potassium is normal, and some patients are combined with hypophosphatemia. Certain factors such as large amount of carbohydrate intake, excessive exercise, exposure to cold environment, mental stress, infection, trauma, etc. can induce TPP; drugs such as insulin, potassium-excreting diuretics, glucocorticosteroids, epinephrine, toxaphene, hairy fruit rutabaga alkaloids, etc. can also induce TPP episodes.
4. Other hyperthyroid myopathies
(1) Hyperthyroidism ophthalmic muscle paralysis: related to autoimmune factors, the main clinical manifestations of extraocular muscle paralysis caused by limited eye movement, diplopia, strabismus, blurred vision, etc., often coexisting with protruding eyes, and there is orbital edema and conjunctival congestion at the time of examination. Exposure of the cornea due to proptosis can cause corneal dryness, inflammation, ulceration and secondary infection, and in severe cases, there can be optic nerve atrophy and blindness.
(2) Hyperthyroidism myasthenia gravis: mostly seen in women. Involved muscles are most common in ophthalmic, facial and swallowing muscles, followed by neck, trunk and limb muscles, which may lead to respiratory arrest in severe cases.
Examination
In addition to the tests required for hyperthyroidism, electromyography, electrocardiogram (EKG), blood potassium, urine potassium, blood phosphorus, and nerve conduction velocity measurement are performed as appropriate.
Diagnosis
The diagnosis can be made on the basis of the history, clinical manifestations and examination of hyperthyroidism.
Differential diagnosis
Most patients with TPP have hyperthyroidism first and then combined with periodic paralysis, and some patients may have periodic paralysis first and then hyperthyroidism, which should be distinguished from familial periodic paralysis and other low-potassium paralysis.
Treatment
The most fundamental measure is to treat the primary disease, i.e. the treatment of hyperthyroidism.
1. General treatment
(1) Avoid high sugar diet.
(2) Avoid satiety.
(3) Do not eat before going to bed.
(4) Avoid cold, strenuous exercise, emotional excitement and infection.
(5) For those whose serum potassium is often <3.5mmol/L, apply antithyroid drugs to treat hyperthyroidism while taking appropriate amount of potassium salts for prevention.
2. Treatment by type
(1) Acute hyperthyroid myopathy: the treatment is more difficult, refer to the hyperthyroid crisis treatment. Need to carry out monitoring rescue, if necessary, tracheotomy, application of ventilator-assisted respiration, but most of the patients died within 1 to 2 weeks.
(2) Chronic hyperthyroid myopathy: symptomatic treatment can be adenosine triphosphate (ATP), coenzyme A and inosine, vitamin E, B, C, etc..
(3) TPP treatment: long-term anti-thyroid medication for hyperthyroid cycle paralysis, sub-total thyroidectomy or radioactive 131I treatment are all applicable to this disease. After the hyperthyroidism is effectively controlled, the cycle paralysis usually does not occur again, and if the hyperthyroidism recurs, the cycle paralysis will appear again. When hyperthyroidism cycle paralysis attack, should first control the symptoms of hyperthyroidism, foreign literature has reported that beta-blocker blocker for the control of symptoms of cycle paralysis, prevention of seizures has a very good efficacy, recommended the application of propranolol 10mg-100mg, tid oral, can be given to oral or intravenous potassium supplementation and oral aminophenazone. After the disease is stabilized, switch to oral potassium salts. Usually the activity of the limb is restored after 1-5h. Those with concomitant hypomagnesemia should be supplemented with magnesium. During the treatment of hyperthyroidism, cardiac glycosides can reduce or prevent the onset of hyperthyroid cycle paralysis.
(4) Hyperthyroidism eye muscle paralysis: the treatment is the same as that of hyperthyroidism synophthalmos.
(5) Hyperthyroidism myasthenia gravis: the treatment of hyperthyroidism and improvement of myasthenia gravis do not have consistent consequences, should be in the treatment of hyperthyroidism at the same time as the treatment of myasthenia gravis, can be applied to the new strychnine, tensilon, and other acetylcholinesterase inhibitor drugs. For patients with longer course, severe myasthenia gravis, and poor drug efficacy, thymus radiation therapy or thymectomy can be considered, but the efficacy is not uniform, and there are large differences in the literature.
3. Diet
During the treatment of the disease, the best way to improve the diet is to eat more light and less salty food, avoiding greasy food, and when the appetite is uncontrollable, choose to eat less and more frequent meals to facilitate the control of the disease.