Serum Creatine Kinase Activity in Thyroid Disorders

Introduction Serum creatine kinase (CK) was first used as a diagnostic aid in progressive muscular dystrophy in 1959 by Ebashi et al (1). It has since become an important Clinical marker for muscle damage. The serum CK level in healthy individuals depends on age, race, lean body mass and physical activity (2, 3). Musculoskeletal disorders often accompany thyroid dysfunction. In addition to the well known observation that these disorders are common in patients with hypothyroidism, they are also observed in patients with thyrotoxicosis (4). Out of some common causes, hypothyroidism is a common cause of an elevated creatine kinase in serum (5). In recent years studies have been conducted to establish a relationship of creatine phosphokinase levels in thyroid diseases (6). A majority of patients with hypothyroidism have been shown to have an increased serum CK (7,8,9,10,11). The exact etiology is not known (12,13,14). Skeletal muscle is affected by hypothyroidism more profoundly in cases of overt hypothyroidism, less so when subclinical hypothyroidism is present (15,16). The assay of creatine kinase activity in serum is extremely valuable in screening hypothyroidism and in present study, an attempt has been made to correlate CK levels with triiodothyronine (T3), thyroxine (T4) and thyroid stimulating hormone (TSH) in hypo and hyperthyroidism. Material and Methods The present study was conducted on 50 patients, out of which 30 were hypothyroid and 20 were hyperthyroid attending the O.P.D. of Himalayan Institute of Medical Abstract Thyroid function and creatine kinase activity was measured in 50 patients of thyroid disorders. The decreased serum levels of triiodothyronine (T3), thyroxine (T4) and increased level of Thyroid stimulating hormone (TSH) in hypothyroid patients is well established but whether there is any correlation of creatine kinase (CK) with hypothyroidism is not well established. Therefore, a study of serum CK and thyroid profile was carried out. In hypothyroid patients with decrease in serum T3, there is a significant increase in CK and findings were reversed in hyperthyroid patients. Serum creatine kinase levels thus, show an inverse relation with serum T3 and T4 levels.