Lactate Dehydrogenase (LD) Isoenzyme Panel - Lactate dehydrogenase (LD) is present in many different organs and tissues such as liver, heart, muscles, kidney, lungs and blood. The usual designation of isoenzymes is LD-I, LD-II, LD-III, LD-IV and LD-V. LD isoenzymes tissue specificity is derived from the fact that LD subunits are synthesized in well-defined ratios and could be used in investigating unexplained causes of Total LD elevations and detection of macro-LD. Do not use LD isoenzymes to detect myocardial injury.