Hypothyroid Myopathy Clinical Presentation

Updated: May 14, 2018
  • Author: Divakara Kedlaya, MBBS; Chief Editor: Stephen Kishner, MD, MHA  more...
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Presentation

History

Neuromuscular symptoms present in 30-80% of patients with hypothyroidism. These symptoms improve or disappear with correction of the hypothyroid state.

Patients may complain of muscle cramping, proximal symmetrical muscle weakness, muscle stiffness, and exercise intolerance. These manifestations can occur at any time during the presentation of hypothyroidism. [12, 20, 21]

Rarely, myopathy may be the sole presenting manifestation of hypothyroidism. [22]

Slowness of muscle relaxation and of muscle contraction are noted in hypothyroid myopathy.

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Physical

Deep tendon reflexes are delayed in approximately 85% of patients with hypothyroidism.

Mounding of the muscle after light percussion (ie, myoedema) occurs in one third of patients with hypothyroidism, but it is not necessarily specific to hypothyroidism.

Muscle enlargement, stiffness, and cramping are a constellation of findings seen in individuals with hypothyroidism. In adults, these findings are known as Hoffman syndrome. [4, 5, 6] In children, they are called Kocher-Debré-Sémélaigne syndrome. [23, 24]

Myokymia, which may be related to a low sodium level, may be seen.

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Causes

See Pathophysiology.

Hypothyroidism can impair mitochondrial metabolism, resulting in decreased muscle energy production. A low thyroid hormone level is the main causative factor. [25]

Certain drugs, such as lipid-lowering medications, may exacerbate myopathy in patients with hypothyroidism. There are reports of an increased risk for statin-induced myopathy in patients with hypothyroidism. Lipid-lowering drugs include beta-hydroxy-beta-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors; also commonly called statins, they include following:

  • Atorvastatin (Lipitor)

  • Fluvastatin (Lescol)

  • Simvastatin (Zocor)

  • Pravastatin (Pravachol)

  • Lovastatin (Mevacor)

Statin-induced myopathy caused by induced hypothyroidism has been reported. [26]

Interferon-alfa therapy for hepatitis, as well as hepatitis infection itself, has been reported to cause a number of adverse immunologic and/or autoimmune effects. [27, 28] Thyroiditis, seen in 10% of patients, may induce hypothyroidism.

Occasionally, hypothyroidism with myopathy may be misdiagnosed as statin intolerance in a patient with dyslipidemia. One must be aware that hypothyroidism can cause both dyslipidemia and myopathy. [29, 30]

Rarely, acute myopathy has been reported to occur with acute hypothyroidism following treatment of Graves disease with radioiodine in adults and adolescents. [31, 32]

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