Consequences of Elevated Luteinizing Hormone on Diverse Physiological Systems: Use of the LH CTP Transgenic Mouse as a Model of Ovarian Hyperstimulation-induced Pathophysiology

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Abstract
Chronically elevated luteinizing hormone (LH) induces significant pathology in the LHCTP transgenic mouse model, which uses the bovine gonadotropin alpha ()-subunit promoter to direct transgene expression specifically to gonadotropes in the anterior pituitary. Previously, it was shown that female LHCTP mice are infertile due to anovulation, develop granulosa cell tumors, and undergo precocious puberty from elevated LH and steroid hormones that fail to completely repress the -subunit promoter. This chapter will discuss recent studies that further elucidate the impact of chronically elevated LH on diverse physiological systems. Granulosa cell tumors induced by elevated LH are strain dependent and prevented when transgenics are treated with human chorionic gonad- otropin (hCG) surges. A granulosa cell tumor-associated transcriptome is generated, revealing several possible gene candidates for ovarian granulosa cell tumorigenesis. Primordial follicles in LHCTP transgenics become depleted and oocytes exhibit increased rates of meiotic segregation defects, although meiotic competency is acquired normally. Anovulation can be rescued in transgenics by superovulation, though pregnancy fails at midgestation due to maternal factors. Uterine receptivity defects prevent implantation of normal embryos following induction of pseuodpregnancy. Transgen- ics develop Cushing-like adrenocortical hyperfunction with increased corticosterone production following induction of adrenal LH receptor expression. Elevated LH acts as a tumor promoter in the gonads and the adrenal gland, when expressed in conjunction with the inhibin- SV40 transgene. Finally, chronic elevated LH promotes mammary tumorigenesis. The understanding of multiple clinical pathologies — including ovarian cancer, perimenopausal reproductive aging, premature ovarian failure, polycystic ovarian syndrome, Cushing's syndrome, and breast cancer — may be enhanced through further study of this useful transgenic mouse model.

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