Hypothyroid myopathy. A clinical and pathologaical study

Area of Science:

• Neurology
• Endocrinology
• Muscle Biology

Background:

• Hypothyroid myopathy presents with muscle weakness and biochemical evidence of hypothyroidism.
• Muscle biopsies reveal characteristic changes including fiber atrophy and mitochondrial abnormalities.

Purpose of the Study:

• To investigate the clinical and pathological features of hypothyroid myopathy.
• To correlate biochemical and histological findings with clinical presentation and response to L-thyroxine treatment.

Main Methods:

• Clinical assessment of ten patients with varying degrees of hypothyroid myopathy.
• Serial percutaneous needle muscle biopsies before and during L-thyroxine treatment.
• Light and electron microscopy, histochemical staining.

Main Results:

• Biochemical hypothyroidism correlated with myopathic severity and type II fiber atrophy.
• Muscle biopsies showed type II fiber atrophy, increased central nuclei, glycogen storage, and mitochondrial abnormalities.
• L-thyroxine treatment led to improvements, with subsarcolemmal mitochondrial changes observed.

Conclusions:

• Hypothyroid myopathy is characterized by reversible glycogen storage and mitochondrial dysfunction.
• Severe muscle weakness and specific histopathological findings may predict delayed recovery.
• Muscle biopsy is crucial for diagnosing and monitoring hypothyroid myopathy.