eMedicine Specialties > Neurology > Neuromuscular Diseases
Endocrine Myopathies: Differential Diagnoses & Workup
Updated: Mar 13, 2007
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
Differential Diagnoses
Other Problems to Be Considered
Cushing disease
Parathyroid disease
Multiple endocrine neoplasia
Steroid myopathy
Hereditary sensory and motor neuropathies
Polymyalgia rheumatica
Workup
Laboratory Studies
- Because the diagnosis is made by elucidating the underlying endocrine abnormality, laboratory studies are considered in relation to the most likely etiologies.
- Laboratory studies measuring hormone levels may help distinguish one endocrine myopathy from another. These tests are best ordered in consultation with an endocrinologist.
- Creatine kinase levels may be normal or increased.
- Hypothyroidism: Creatine kinase usually is elevated markedly.
- Hyperthyroidism: Creatine kinase usually is normal.
Imaging Studies
- Imaging studies neither confirm nor exclude the presence of muscle disease. They may be of benefit in the diagnosis of endocrine disorders.
Other Tests
- Electromyography (EMG) may reveal the presence of a myopathy, although a normal examination does not rule out the diagnosis. Although commonly performed with nerve conduction study testing, needle EMG is direct, invasive testing of muscle and therefore differs from nerve conduction study testing. Myopathy is a disorder of muscle, and the nerve conduction study portion of the electrophysiological examination should be normal; however, the endocrinopathies often also cause neuropathies or may be associated with other conditions (such as diabetes) in which neuropathies are common. This heterogeneity explains the great variability and lack of consensus regarding the electrophysiological findings in endocrine disease.
- Needle EMG examination preferentially studies the type I units, as these units fire selectively during weak muscle contraction. Thus, a disease process selectively involving type II units, such as steroid myopathy, may reveal no abnormalities on EMG.
- EMG findings consistent with a myopathic process include the following:
- Polyphasic motor unit potentials
- Shortened duration of motor unit potentials
- Decreased amplitude of motor unit potentials
- Adrenal dysfunction: In cases of adrenomyeloneuropathy, a distinct and different disorder not otherwise considered in this article, nerve conduction velocity may be normal or decreased.
- Hypothyroidism: EMG helps differentiate delayed muscle relaxation from myotonia.
- Hyperthyroidism: EMG abnormalities may be found more proximally and are of the typical myopathic type. Motor conduction studies typically are normal, although some find distal leg denervation.
- Hyperparathyroidism: The usual finding is myopathic motor unit potentials and increased frequency of polyphasic potentials without spontaneous activity. However, patients with severe proximal weakness and bulbar involvement may have fasciculations and a reduced recruitment pattern with normal nerve conduction velocities.
Histologic Findings
Muscle biopsy is considered mainly to exclude other treatable or congenital muscle diseases, including myotonic dystrophy or congenital myopathies. Histologic changes associated with endocrine myopathies are variable and rarely are specific.
- Hyperthyroidism - Normal histology versus nonspecific findings
- Hypothyroidism - Nonspecific type II muscle fiber atrophy, occasionally with glycogen storage
- Steroid myopathy - Nonspecific type II muscle fiber loss, sometimes with lipid storage
- Thyrotoxic periodic paralysis - Vacuolar dilation of the sarcoplasmic reticulum
- Corticosteroid therapy - Rapid evolving myopathy with myosin-deficient muscle fibers. (This was reported by al-Lozi et al in 5 patients who received corticosteroid therapy.)
More on Endocrine Myopathies |
| Overview: Endocrine Myopathies |
 Differential Diagnoses & Workup: Endocrine Myopathies |
| Treatment & Medication: Endocrine Myopathies |
| Follow-up: Endocrine Myopathies |
| References |
| « Previous Page | Next Page » |
References
Aminoff MJ. Electromyography in Clinical Practice. 3rd ed. Churchill Livingstone;1998.
Benvenga S, Toscano A, Rodolico C, et al. Endocrine evaluation for muscle pain. J R Soc Med. Aug 2001;94(8):405-7. [Medline].
Engel AG, Fransini-Armstrong C. Endocrine myopathies. In: Myology. Vol 2. McGraw-Hill;1994:1726-47.
Engel AG. Electron microscopic observations in primary hypokalemic and thyrotoxic periodic paralyses. Mayo Clin Proc. Nov 1966;41(11):797-808. [Medline].
Engel AG, Fransini-Armstrong C, eds. Endocrine myopathies. In: Myology. 2nd ed. McGraw-Hill;1994.
Fenichel GM. Clinical Pediatric Neurology: A Signs and Symptoms Approach. 2nd ed. WB Saunders Co;1993.
Ghilardi G, Gonvers JJ, So A. Hypothyroid myopathy as a complication of interferon alpha therapy for chronic hepatitis C virus infection. Br J Rheumatol. Dec 1998;37(12):1349-51. [Medline].
Godby A, Bergstresser PR, Chaker B, Pandya AG. Fatal scleromyxedema: report of a case and review of the literature. J Am Acad Dermatol. Feb 1998;38(2 Pt 2):289-94. [Medline].
Horak HA, Pourmand R. Endocrine myopathies. Neurol Clin. Feb 2000;18(1):203-13. [Medline].
Ikeda H, Yoshimoto T, Ogawa Y, et al. Clinico-pathological study of Cushing''s disease with large pituitary adenoma. Clin Endocrinol (Oxf). Jun 1997;46(6):669-79. [Medline].
Imrich R, Bosak V, Rovensky J. Polymyalgia rheumatica and temporal arteritis: the endocrine relations and the pathogenesis. Review. Endocr Regul. Sep 2006;40(3):83-9. [Medline].
Mastaglia FL. Endocrine myopathies. In: Lord Walton of Detchant, ed. Skeletal Muscle Pathology. 2nd ed. Churchill Livingstone;1992:493-509.
Mastaglia FL. Endocrine myopathies In: Skeletal Muscle Pathology. Churchill Livingstone;1992.
McNab TL, Khandwala HM. Acromegaly as an endocrine form of myopathy: case report and review of literature. Endocr Pract. Jan-Feb 2005;11(1):18-22. [Medline].
Ohkoshi N, Ishii A, Shiraiwa N, et al. Dysfunction of the hypothalamic-pituitary system in mitochondrial encephalomyopathies. J Med. 1998;29(1-2):13-29. [Medline].
Poirier J, Gray F, Escourolle R. Manual of Basic Neuropathology. WB Saunders Co;1990.
Pourmand R. Metabolic myopathies. A diagnostic evaluation. Neurol Clin. Feb 2000;18(1):1-13. [Medline].
Rodolico C, Toscano A, Benvenga S, et al. Myopathy as the persistently isolated symptomatology of primary autoimmune hypothyroidism. Thyroid. Nov 1998;8(11):1033-8. [Medline].
Saguil A. Evaluation of the patient with muscle weakness. Am Fam Physician. Apr 1 2005;71(7):1327-36. [Medline].
Schapira AH, Griggs RC. Endocrine myopathies. In: Muscle Disease. Vol 6. Butterworth-Heinemann;2000:181-92.
Siafakas NM, Alexopoulou C, Bouros D. Respiratory muscle function in endocrine diseases. Monaldi Arch Chest Dis. Apr 1999;54(2):154-9. [Medline].
Van Linthoudt D, Schumacher HR Jr, Algeo S, et al. Scleromyxedema with myopathy and hyperthyroidism. J Rheumatol. Jul 1996;23(7):1299-301. [Medline].
al-Lozi MT, Pestronk A, Lee WC, et al. Rapidly evolving myopathy with myosin-deficient muscle fibers. Ann Neurology. Mar 1994;35(3):257-9. [Medline].
Further Reading
Keywords
endocrine myopathy, adrenal dysfunction, Cushing disease, Cushing syndrome, steroid myopathy, thyroid dysfunction, myxedema coma, thyrotoxic myopathy, parathyroid dysfunction, multiple endocrine neoplasia, pituitary dysfunction, islands of Langerhans dysfunction, diabetic myopathy, ischemic infarction of the femoral muscles, hypoadrenalism, muscle weakness, adrenal insufficiency, hyperadrenalism, thyroid hormone deficiency, hypoparathyroidism, hyperparathyroidism, hypopituitarism, hyperpituitarism, hyperparathyroid myopathy, hyperthyroid myopathy, iatrogenic steroid myopathy, hypothyroid myopathy, Cushing myopathy
