Serum enzyme alterations in hypothyroidism before and after treatment

Recognition of a pattern of elevations in commonly measured serum enzymes [creatine phosphokinase (CPK), lactic dehydrogenase (LDH), and glutamate oxalacetate transaminase (SGOT)] can facilitate the diagnosis of hypothyroidism, especially when muscle weakness is a symptom. Elevated levels of serum cholesterol, total protein, and albumin further contribute to a chemical profile of hypothyroidism, which can be observed in a routine chemistry screening test such as that obtained with the SMA 12/60 AutoAnalyzer. An illustrative case concerns a 50-year-old man who presented with angina pectoris and leg weakness. Subsequently he was found to have severe hypothyroidism. Special attention is given to the serum enzyme values which initially were elevated and fell to normal levels during thyroid replacement therapy. Isoenzyme fractionation of LDH and CPK indicated skeletal muscle as the source of the elevated enzyme activity. The literature on enzyme abnormalities in hypothyroidism is reviewed, with special reference to hypothyroid myopathy.