Immunohistochemical localization of a human chorionic gonadotropin-like substance in the human pituitary gland

A substance with the biological, immunological, and physicochemical properties similar to those of hCG (hCG-like substance) has been found in human pituitary homogenates and urine of nonpregnant subjects. The purpose of the present study was to localize the hCG-like substance in human pituitary gonadotropin producing cells (gonadotrophs) by using an unique antiserum raised against a synthetic hCG beta C-terminal peptide (P75R). Twenty-five pituitary glands were obtained at autopsy from women of various chronological ages. An immunohistochemical method was employed for localizing hLH, hFSH, and an hCG-like substance on the horizontal serial sections of the pituitary glands. The LH and FSH cells were indistinguishable with the antisera employed in the present study. The hCG-like substance was only localized in the cytoplasm of the gonadotrophs, rather commonly when the pituitary glands from postmenopausal women were examined. The P75R serum pretreated with excessive amount of native hCG failed to exhibit the immunostaining. Normal human tissues aside from pituitary glands did not react with the P75R serum. The results obtained in the present study and those reported by others may indicate that the hCG-like substance present in human pituitary glands is the precursor of hLH.