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Hypothyroid Myopathy Workup

  • Author: Divakara Kedlaya, MBBS; Chief Editor: Stephen Kishner, MD, MHA  more...
Updated: Apr 07, 2015

Laboratory Studies

Nerve conduction studies may show decremental response to low-rate nerve stimulation and incremental response to high-rate nerve stimulation, suggesting some neuromuscular junction abnormality.

Needle electromyography is usually normal or may be mildly myopathic. Myotonia may be present in rare cases.[28]

Increased thyroid stimulating hormone (TSH) is seen in primary hypothyroidism, and decreased TSH is seen in pituitary-hypothalamic disease with secondary hypothyroidism.

Low free T4 and T3 levels, as well as a low total T4 level and a free T4 index, are seen. The degree of myopathy is not necessarily correlated to the degree of hypothyroidism.

The creatine kinase level can be very high (10-100 times greater than the normal level) in some patients, but it has no correlation with weakness.[3] . The level returns to normal with adequate treatment.[29]


Histologic Findings

Histologic findings on muscle biopsy are nonspecific. Pale central regions on nicotinamide adenine dinucleotide with accumulation of periodic acid-Schiff – positive material are seen. Decreased numbers of beta-adrenergic receptors are observed and are accompanied by glycogenolysis. Some muscle fiber atrophy is noted, and increased numbers of internal nuclei, glycogen aggregates, and (occasionally) deposition of mucopolysaccharides in the connective tissue are characteristic of hypothyroid myopathy.[30]

Contributor Information and Disclosures

Divakara Kedlaya, MBBS Clinical Associate Professor, Department of Physical Medicine and Rehabilitation, Loma Linda University School of Medicine; Medical Director, Physical Medicine and Rehabilitation and Pain Management, St Mary Corwin Medical Center

Divakara Kedlaya, MBBS is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation, Colorado Medical Society, American Association of Neuromuscular and Electrodiagnostic Medicine

Disclosure: Nothing to disclose.


Diana Echeverry, MD, MPH Assistant Professor, Department of Endocrinology, Charles Drew University of Medicine and Science

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Kat Kolaski, MD Assistant Professor, Departments of Orthopedic Surgery and Pediatrics, Wake Forest University School of Medicine

Kat Kolaski, MD is a member of the following medical societies: American Academy for Cerebral Palsy and Developmental Medicine, American Academy of Physical Medicine and Rehabilitation

Disclosure: Nothing to disclose.

Chief Editor

Stephen Kishner, MD, MHA Professor of Clinical Medicine, Physical Medicine and Rehabilitation Residency Program Director, Louisiana State University School of Medicine in New Orleans

Stephen Kishner, MD, MHA is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation, American Association of Neuromuscular and Electrodiagnostic Medicine

Disclosure: Nothing to disclose.

Additional Contributors

Elizabeth A Moberg-Wolff, MD Medical Director, Pediatric Rehabilitation Medicine Associates

Elizabeth A Moberg-Wolff, MD is a member of the following medical societies: American Academy for Cerebral Palsy and Developmental Medicine, American Academy of Physical Medicine and Rehabilitation

Disclosure: Nothing to disclose.

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