In accordance with the present results, previous studies have demonstrated an elevated or normal LH concentration in cases of spermatogenic or gonadal failure in men and dogs (13, 71) and a decreased LH concentration in association with hypogonadotropic hypogonadism in men (71) and hypopituitarism in the male dog (17). This evidence concerns the gene PLOD1 and hypogonadotropic hypogonadism.