Effect of Dehydroepiandrosterone on Ovulation in the Immature Female Rat

Abstract

One of. the most common cause~ bf infertility and associated reproductive .disorders encouritered in medicine and in ~eterinary "practice is the c·ystic ov·ary. The precise factors causing the development of ovarian cysts are ill under~tood brit the delicate balance which exists bet\veen the pituitary and .the gonad is involved. In addition, excessive.androgen production frequently results in similar cystic changes ~pppled ~ith ovulatory ·faiiure. J.Jong term administration of DBA to immature female· rats resulted in one precqcious ovulation followed by ovulatory failure and cystic ovarian changes. Discontinuation of the androgen pro~uced. a ~eries of irregular cycles followed by the resumption of normal cyclic estrus. After the first several days of treatment gon~dotrophin levels remained tonic, indicating that the initial effect of the androgen occurred soon after axial exposure. This possibility was investigated with a series of short ter~ experiments in which 60 mg/kg of DHA was· administered to immature female rats beginning on day twenty..,.seven of age. Precocious ovulation was observed both in animals with and without PHS priming. Gonadotrophin values remained tonic in the DHA + PMS groups, however, a significant pituitary depletion of LH was found .prior to ovulation when DHA was given alone. Inhibition of ovulation iri the DHA + PMS group by sodium-phenobarbital indicatedthat endoienous gonadotrophins were involved even though no depletion could be demonstrated. In "this case tonic glandular .levels must be taken as evidence of increased hypophyseal synthesis. Although present assay methods do not allow an overly specific pi~-pointing of androgen action at the hypothalamic-pituitary level, they do indicate a disruption in nor~~l rhythmic activity. It is reasonable that this disruption is sufficient to cause ovulatory failure and cystic ovarian modification.