Health check revealed elevation of creatine kinase related to hypothyroidism.

Abstract

Summary: It is relatively rare to find a significant increase in creatine kinase (CK) related to hypothyroidism through a health examination. This case report describes an asymptomatic adult patient in whom an asymptomatic elevation of serum CK was discovered incidentally during a routine health check. The patient reported no significant muscle weakness, pain, or other classic symptoms of proximal myopathy or hypothyroidism. A comprehensive diagnostic workup was initiated to investigate the common causes of high CK level, including cardiac injury, strenuous exercise, statin use, and inflammatory myopathies, all of which were excluded. Thyroid function tests revealed severe primary hypothyroidism with significantly elevated thyroid-stimulating hormone (TSH; >100 mIU/L) and decreased free thyroxine levels. A diagnosis of hypothyroid myopathy was established. Upon initiation of levothyroxine replacement therapy, the patient's thyroid function normalized, and this was followed by a complete normalization of the serum CK level on subsequent follow-up. This case highlights that hypothyroidism is an important, reversible, notable, and treatable cause of an asymptomatic unexplained CK elevation, particularly in the context of severe biochemical hypothyroidism. It underscores the critical importance of including thyroid function tests in the routine differential diagnosis of any unexplained high CK level, even in the absence of overt clinical myopathic symptoms or recognized signs of hypothyroidism. For clinicians and general practitioners interpreting routine health screening results, this case serves as a vital reminder that a simple thyroid function test can prevent unnecessary and costly investigations and lead to the correct diagnosis and effective treatment.

Learning points: In asymptomatic individuals undergoing routine health screening, an isolated elevation of creatine kinase (CK) may be an early biochemical indicator of underlying hypothyroidism, warranting simple thyroid function testing. This case underscores the public health value of routine biochemical panels that include CK, as they can identify individuals with subclinical endocrine dysfunction before the development of overt clinical disease. For primary care and preventive medicine physicians, integrating thyroid function tests into the initial workup for incidentally discovered hyperCKemia is a cost-effective strategy that can prevent unnecessary specialist referrals and invasive investigations.