SERUM ENZYMES IN HYPOTHYROIDISM

Aim. To report three cases of hypothyroidism detected because of unexp lained elevation of serum enzyme levels on biochemical testing. Method s. Clinical details and serum enzyme results were obtained before and after L-thyroxine (T4) replacement therapy. Results. The three patient s all had serum creatine kinase (CK) levels >2000 U/L, aspartate amino transferase (AST) >90 U/L, and lactate dehydrogenase (LD) >300 U/L at presentation, with these levels being 10-15, 2-6, and 2-3 times the up per reference limits respectively. CK isoenzyme determination was cons istent with skeletal muscle origin. Thyroid function tests performed a fter consultation with the clinical biochemist confirmed the biochemic al diagnosis of primary hypothyroidism. A rapid fall toward normal ser um enzyme levels occurred in response to T4 replacement therapy. Concl usions. Although serum enzymes are an integral part of both the liver and cardiac profiles provided by laboratory, they are not organ specif ic, and changes may reflect dysfunction elsewhere in the body. Elevati ons of serum CK (land other muscle enzymes) may occur in hypothyroid s ubjects, the cause of which has not been established. The clinical dia gnosis of hypothyroidism requires a high index of suspicion and should be considered in patients with unexplained persistent elevations of s erum muscle enzymes.