Assessment of Serum Creatine Kinase (CK) and Lactate Dehydrogenase (LDH) Levels in Patients with Thyroid Disorders: A Hospital-Based Study from Bihar

Background: Thyroid dysfunctions are among the most common endocrine disorders worldwide, with hypothyroidism and hyperthyroidism producing systemic metabolic effects. Thyroid hormones influence nearly all metabolic pathways, and their imbalance often leads to muscular involvement. Serum enzyme markers such as Creatine Kinase (CK) and Lactate Dehydrogenase (LDH) reflect these muscular and metabolic changes and may serve as useful adjuncts in evaluating thyroid disease severity. Aim: To evaluate and compare serum levels of CK and LDH in patients with thyroid disorders and healthy controls, and to assess their correlation with thyroid hormone levels (TSH, T3, and T4). Methods: This prospective observational study was conducted in the Departments of Biochemistry and Endocrinology, IGIMS, Patna, over a period of 18 months (February 2020–July 2021). A total of 150 participants were enrolled, including 100 cases (70 hypothyroid, 30 hyperthyroid) and 50 age- and sex-matched healthy controls. Serum TSH, total T3, and T4 were estimated by Chemiluminescent Microparticle Immunoassay (CMIA) on Abbott Architect i2000SR, while CK and LDH were measured using Beckman Coulter AU5800 based on the IFCC method. Data were analyzed using SPSS version 23.0, applying t-tests, ANOVA, and Pearson’s correlation, with p < 0.05 considered statistically significant. Results: The mean serum TSH was significantly higher in hypothyroid patients (18.9 ± 9.4 µIU/mL) and lower in hyperthyroid patients (0.16 ± 0.08 µIU/mL) compared to controls (2.6 ± 1.2 µIU/mL). Serum CK and LDH levels were markedly elevated in hypothyroid patients (246.8 ± 88.6 IU/L and 384.5 ± 105.4 IU/L, respectively) compared to controls (109.2 ± 42.3 IU/L and 172.4 ± 33.7 IU/L; p < 0.001). Hyperthyroid patients showed decreased CK (78.4 ± 29.1 IU/L) but mildly elevated LDH (265.7 ± 58.2 IU/L). CK and LDH correlated positively with TSH (r = +0.74 and +0.61, respectively) and negatively with T3 and T4 levels (p < 0.001). Conclusion: Serum CK and LDH levels are significantly increased in hypothyroid patients, indicating skeletal muscle involvement and metabolic disturbance. These enzymes correlate strongly with thyroid dysfunction severity and may serve as valuable adjuncts in assessing muscular and metabolic changes associated with thyroid disorders. Recommendations: Routine estimation of CK and LDH in thyroid patients is recommended to detect early myopathic involvement, monitor disease progression, and assess treatment response, particularly in overt hypothyroidism. Keywords: Thyroid disorders; Hypothyroidism; Creatine kinase; Lactate dehydrogenase; Muscle enzymes.