Hypothyroid Myopathy

Very common (up to 80% ) in patients with hypothyroidism

Pathophysiology:

 • T4 deficiency leads to abnormal glycogenotysis & mitochondrial oxidative metabolism which impairs musde function

 • Selective atrophy of fast-twitching Type II fibers (glycolysis dependent) and hypertrophy of slow-twitching Type I muscle fibers

Spectrum of Clinical Manifestations

Asymptomatic CK Elevations → Myalgias (common) → Symmetric, proximal myopathy → Muscle hypertrophy → Rhabdomyolysis (rare)



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