Absence of sperm-specific lactate dehydrogenase-x in patients with testis cancer

LDH-x is a unique form of lactate dehydrogenase found in germinal epithelium during spermatogenesis. 53 patients with germ cell tumors were screened for the presence of LDH-x in the serum. No patient had detectable levels of the enzyme. 31 of the patients had elevated total serum LDH levels, and the isozyme fraction type 1 and/or type 2 was responsible for the elevation in all cases. LDH is a useful marker in germ cell tumors, but LDH-x is not the responsible isozyme.