Understanding Muscle Pain and Weakness in Thyroid Disease

Muscle disease, or myopathy, may occur because you have an underactive thyroid (hypothyroidism) or an overactive thyroid (hyperthyroidism). Muscle problems related to these medical conditions are usually mild. Treatment of your thyroid disorder can help ease the symptoms.

However, in some rare cases, myopathy related to thyroid disease can be severe and debilitating.

By gaining a better understanding of the muscle symptoms of thyroid disease, you'll be able to manage your discomfort or weakness.

This article will talk about thyroid disease and how it can cause pain and weakness. It will discuss thyroid muscle disease symptoms and how a healthcare provider diagnoses and treats the disease.

Myopathy in Thyroid Disorders

Verywell / Laura Porter

Myopathy in Hypothyroidism
  • Weakness in muscles close to the center of the body (thighs, shoulders)

  • Elevated creatinine

  • Cramping

  • Rarely, enlarged muscles (Hoffman's syndrome)

  • Rarely, breakdown of muscle tissue (rhabdomyolysis)

Myopathy in Hyperthyroidism
  • Muscle weakness

  • Creatinine levels tend to be normal

  • Cramping (uncommon)

  • Rarely, issues with the muscles involved in swallowing and breathing (rare)

Hypothyroid Myopathy

Muscle weakness, aches, and cramping are common in people with hypothyroidism.

Symptoms

People with hypothyroid myopathy can experience weakness throughout the body, and it is typically most severe in the muscles of the thighs or shoulders. This can lead to problems climbing stairs or combing your hair.

High Creatinine Kinase Levels

In addition to muscle symptoms, you may have a high creatinine kinase level, which is measured with a blood test. Creatinine kinase is a muscle enzyme that is released into the blood when there is a muscle injury. But your creatinine kinase level is not necessarily linked to the severity of your muscle pain.

Rarely, hypothyroidism can cause severe muscle symptoms. One example is Hoffman's syndrome. This is when a person develops muscle hypertrophy (enlarged muscles). It can lead to significant muscle stiffness, weakness, and pain.

Rhabdomyolysis, a condition where muscle breaks down rapidly, is a rare complication of hypothyroidism. It's often triggered by the combination of being hypothyroid and doing strenuous exercise. It may also occur when people take a statin, which is a cholesterol-lowering medication.

Causes

The exact cause of hypothyroidism-induced myopathy isn't known, but some experts believe that the thyroxine (T4) deficiency seen in hypothyroidism leads to muscle injury and impaired muscle function.

Diagnosis

Hypothyroid myopathy is diagnosed based on symptoms, physical examination, and diagnostic tests. You may have a blood test to measure creatinine kinase.

Your healthcare provider may recommend other tests, such as electromyography. This is a test that uses needles to measure the electrical signals in your muscles and nerve cells while they're active and at rest.

With a muscle biopsy, a small sample of muscle is removed with a minor surgical procedure for microscopic examination. This procedure is safe. You may have a biopsy if your symptoms are severe and your diagnosis is not clear based on less invasive testing.

Treatment

Treatment with the thyroid hormone replacement medication Synthroid (levothyroxine) can usually improve symptoms. It may take weeks for cramps and stiffness to improve. It usually takes several months for muscle weakness to improve.

Hyperthyroid Myopathy

Hyperthyroidism can also cause muscle weakness and sometimes cramping, but the symptoms tend to differ from myopathy related to hypothyroidism.

Symptoms

Muscle weakness in the shoulders and hips is the main symptom in people with hyperthyroidism. While muscle cramps and aches may occur, they are not as common as they are with myopathy that's related to hypothyroidism.

Muscle weakness from hyperthyroid myopathy causes difficulty climbing stairs, rising from a chair, holding or gripping objects, and trouble reaching arms above the head.

People with hyperthyroid myopathy may experience weakness in the throat, face, and respiratory muscles. Rarely, the weakness can involve the muscles that help you swallow and breathe.

Causes

The causes of myopathy with hyperthyroidism are not well understood. It's been suggested that high thyroid hormone levels may lead to increased breakdown of muscle protein, as well as greater muscle energy use.

Diagnosis

As with myopathy in hypothyroidism, your healthcare provider will ask you about your muscle symptoms and perform a physical examination.

They may also order blood tests, such as thyroid function panel. The blood creatinine kinase level is generally normal with hyperthyroid myopathy. Your healthcare provider may recommend electromyography.

Thyroid Disease Doctor Discussion Guide

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Treatment

Treatment of your hyperthyroidism will generally cure hyperthyroid myopathy. However, it can take time to improve—possibly up to several months—even after the thyroid is functioning normally again.

Summary

When you have thyroid disease, you might experience muscle weakness and pain, especially if your thyroid hormone levels are not where they should be. Hypothyroid myopathy tends to cause muscle weakness in the larger muscles of the body, typically the shoulders and thighs. Hyperthyroid myopathy causes muscle weakness throughout the body that may rarely affect the muscles that control swallowing and breathing.

Both types of myopathy improve with treatment of the underlying thyroid disease, but it can take time for symptoms to get better.

A Word From Verywell

Muscle complaints are common in thyroid disease. They can usually be soothed when your thyroid starts to function normally again. Coping strategies for easing muscle pain, regardless of the cause, may be useful in the meantime. Things like drinking enough fluids, a massage, warm baths, and gentle exercise are good ways to help with the pain. Taking magnesium supplements can also soothe muscle cramps.

Still, it's important to see your healthcare provider if you notice new or significant muscle pain or weakness. While your thyroid may be the cause of your pain and weakness, there are other health conditions that can cause muscle symptoms as well. 

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7 Sources
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