Hypothyroid myopathy with a strikingly elevated serum creatine kinase level

Area of Science:

• Endocrinology
• Neurology
• Muscle Diseases

Background:

• Hypothyroid myopathy typically presents with mild elevations in serum creatine kinase (CK).
• Markedly elevated CK levels are uncommon in hypothyroidism and usually suggest other myopathic processes like inflammatory myopathies or muscular dystrophies.

Observation:

• A patient presented with progressive proximal muscle weakness and an exceptionally high serum CK level exceeding 29,000 IU/L.
• Initial presentation did not exhibit overt systemic signs or symptoms of hypothyroidism.

Findings:

• Laboratory evaluation revealed profound hypothyroidism as the underlying cause of the severe hyperCKemia.
• Thyroid hormone replacement therapy led to complete resolution of muscle weakness and a significant decrease in serum CK levels.

Implications:

• This case highlights that severe hyperCKemia can be a manifestation of hypothyroidism.
• Assessing thyroid function is essential in patients with unexplained muscle weakness and elevated CK, irrespective of the CK level or presence of overt hypothyroid symptoms.
• Undiagnosed hypothyroidism can lead to potentially reversible severe muscle damage.