Serum levels of Mullerian inhibiting substance in boys with cryptorchidism.

Serum levels of Mullerian inhibiting substance (MIS) were measured in boys with cryptorchidism (n = 104) and paired, age-matched controls (n = 104) using an enzyme immunoassay. Control MIS levels were high during the first year of life with a peak level at 4 to 12 months, subsequently diminishing with age. MIS levels in patients with undescended testes also declined with age, although a surge was not found in the first year. Mean MIS concentration of cryptorchid boys was significantly lower than controls (P less than .001). There was a significant reduction of the mean MIS level in children with bilateral cryptorchidism compared with those with unilateral undescended testis (P less than .05). These differences might support the hypothesis that MIS initiates transabdominal testicular descent. However, because most undescended testes are probably the result of anatomical or functional abnormalities during transinguinal testicular descent, differences in MIS levels more likely result from secondary testicular degeneration. In the future, MIS immunoassay should play an important role in the investigation of gonadal function in boys with various genital disorders, including cryptorchidism.