Background: Hypothyroidism is one of the most commonly occurring endocrine disorders, worldwide. The disorder is associated with a wide range of muscular involvement varying from myalgia to true myopathy. Biochemical parameters such as serum Creatine Kinase (CK), a sensitive marker of muscle damage and serum Lactate Dehydrogenase (LDH), a general marker of tissue damage can be measured to assess the muscular involvement in hypothyroidism. In this study serum CK and LDH activities to assess the muscular involvement in hypothyroidism and to evaluate their relationship with T₃, T₄ and TSH. Materials and methods: Fifty, clinically diagnosed hypothyroidism patients with symptoms suggestive of muscle involvement were taken as cases and fifty sex and age matched, apparently healthy volunteers with normal thyroid function tests (TFT) were taken as controls. Biochemical estimations of triiodothyronine (T₃), thyroxine (T₄), thyroid stimulating hormone (TSH), serum CK and serum LDH were done. Results: T₃, T₄ levels and serum CK and LDH activities were within the reference range in both the study groups. In seven cases high TSH with low T₄ values were observed. Significant difference in serum CK and LDH activities were observed in these seven cases compared to rest of the forty-three cases. Even though there was no significant difference among the study groups (cases and controls), a weak positive correlation of CK, LDH with TSH levels and weak negative correlation with T₃ and T₄ levels were observed. Conclusion: Hormone replacement therapy shall be optimized to treat muscular involvement if serum CK and LDH activity is found to be elevated with low T₄ levels, where as normal serum CK and LDH activity with normal T₄ levels indicates that the thyroid treatment is optimized (serum T₃ and T₄ levels has come to the reference range though TSH is mildly elevated) and if the subject is still complaining of muscular symptoms, then other underlying causes for muscular involvement shall be ruled out.