Induction of ovarian tumors by endogenous gonadotropins in rats bearing intrasplenic ovarian grafts.

In this study the role of gonadotropins for the induction of ovarian tumors in rats was examined. The rats were castrated and one ovary was transplanted under the splenic capsule. Rats remained untreated or received a GnRH analog for gonadotropin suppression either immediately, 90 or 180 days after castration. Under these conditions the untreated rats developed ovarian tumors while the treated rats only developed tumors when the stimulation of gonadotropins lasted for more than 90 days. The first appearing tumors were theca cell tumors while during the further course of the experiment the granulosa cell compartment increased; however, no histological signs of malignancy could be detected in these tumors. GnRH analogs could block the induction of granulosa cell tumors when administered 150 days after transplantation. After a period of 210-240 days the tumors grew independently of elevated LH and FSH levels. The causes of this growth autonomy need to be studied further.