[Misinterpretation of elevated serum creatine kinase level in secondary hypothyroidism]

An elevation of serum creatine kinase (CK) level is diagnosed in about every third patient with hypothyroidism. This is a well-known laboratory finding which is described in all standard books of internal medicine. Nevertheless it is difficult to diagnose an indistinct elevation of serum CK if a cardiac event is excluded and especially diseases of skeletal muscle system are considered in differential diagnoses. Despite better knowledge a hypothyroidism is rejected in cases of normal basic TSH level although typical clinical signs in addition to myopathic pain are available. Describing three patients with secondary hypothyroidism we want to demonstrate the danger of overestimating laboratory parameters by ignoring clinical symptoms.

Three patients came under medical observation due to unclear elevation of serum CK. Additional therapy with CSE inhibitors in two of the three patients led to the wrong conclusion as drug-specific side effect. The basic TSH level was normal in all patients, the main reason for late diagnosis of secondary hypothyroidism.

Paying attention to clinical signs of hypothyroidism is elementary in cases of elevation of serum CK level. The secondary cause of hypothyroidism on basis of anterior pituitary gland insufficiency has to be included in differential diagnoses.