Inhibition of Hypothalamic LHRH Depletion after Ovariectomy by Transplantable Prolactin and Growth-Hormone-Secreting Tumors

Abstract Anestrous Wistar-Furth rats bearing implants of the Furth MtTW15 tumor and diestrous tumor-free rats were ovariectomized and serum luteinizing hormone (LH), follicle-stimulating hormone (FSH) concentrations, and hypothalamic luteinizing hormone-releasing hormone (LHRH) content, were studied. The increase of LH and FSH, after ovariectomy, was significantly greater in tumor-free rats than in rats bearing prolactin secreting tumor implants. The hypothalamic LHRH content of the intact tumor-bearing rats was greater (P < 0.01) than that of tumor-free rats. Furthermore, the depletion of hypothalamic LHRH content was greater in tumor-free rats than in tumor-bearing rats. These results suggest that this prolactin and growth-hormone-secreting tumor prevents gonadotropin release by reducing LHRH release from the hypothalamus.