Hypothyroid Myopathy, in the Setting of Inflammatory Arthropathy: A Case Report

Case Diagnosis: A 76-year-old African American female with hypothyroid myopathy.

Case Description or Program Description: Patient presented to an acute hospital for a decompensated heart failure exacerbation due to medical noncompliance, with a history of hypothyroidism, focal epilepsy, and DVT on long-term warfarin. She had worsening proximal hip and shoulder girdle weakness and stiffness, impeding ambulation and ADLs.

Setting: Tertiary rehabilitation hospital

Assessment/Results: Labs revealed a CK of 1835 U/L, TSH of 75 mIU/L, T3 below 0.4 pg/mL, T4 of 0.1 ng/dL and a positive ANA, CRP and rheumatoid factor. Bilateral thigh MRI showed extensive generalized nonspecific muscle edema in both upper legs. Bilateral hand and wrist x-ray revealed soft tissue swelling with erosive changes consistent with rheumatoid arthritis. She was treated with IV levothyroxine with transition to PO levothyroxine. The remainder of her myositis, dermatomyositis, and autoimmune panel was negative. She was discharged to an inpatient rehabilitation program, where she continued to progress with her ambulation, ADLs, problem solving, and memory recall strategies for a safe return to home.

Discussion (relevance): The pathogenesis of hypothyroid myopathy is not completely understood, but is suspected that T4 affects energy metabolism, and its deficiency impairs muscle function with selective atrophy of type II fibers. With appropriate treatment, strength and CK improvements can be seen to precede normalization of thyroid function tests. Women are affected by this disease more frequently than men, and it can be seen at any age. No predilection for any particular race has been noted. Additionally, while seropositive RA likely played a role in the patient’s presentation, her clinical improvement with levothyroxine helps confirm the diagnosis. She will follow up with rheumatology for discussion of immunomodulatory therapy.

Conclusions: Muscle involvement in hypothyroidism is common; affecting almost 80 percent of patients. Hypothyroid myopathy is often missed and mistaken for fatigue or lassitude when clinicians fail to ask about muscle-related symptoms.