Endocrine and ultrasound evaluation of a non-cycling African elephant: Identification of an ovarian follicular cyst

The reproductive rate of captive African elephants is :low because of logis tical difficulties associated with transporting animals for breeding, the d anger of maintaining bulls and medical or physiological problems. There als o is growing evidence that a significant number of mature female elephants are not experiencing normal estrous cycles. The case described in this :rep ort involves the diagnosis and attempted treatment of an ovarian follicular cyst in an African elephant at the Pittsburgh Zoo. On the basis of serum p rogesterone analysis, the female exhibited regular ovarian cycles from July 1993 through March 1994, but from November 1994 to the present has not sho wn any evidence of reproductive cyclicity. In April 1996, a large follicula r structure was identified on the right ovary using transrectal ultrasound. In an attempt to luteinize the cyst, 500 mu g gonadotropin-releasing hormo ne (GnRH) was administered intravenously in October 1996, which stimulated a modest increase in serum luteinizing hormone (LH) (approximately twofold over baseline), but no resumption of ovarian activity. The elephant was tre ated again 5 months later with a higher dose of GnRH (5 mg, i.v.) with the same results. An ultrasound evaluation in July 1997 indicated the structure was still present. In October 1997, the female was given human chorionic g onadotropin (hCG; 10,000 TU, i.m.), which induced estrus and breeding, but no ovulation or luteinization of the cyst, and she remains acyclic. These r esults suggest that conventional methods developed in other species for tre ating ovarian follicular cysts may not necessarily be effective in the elep hant. It is also important that reproductive age females be monitored via c ontinuous progesterone analysis and occasional reproductive tract ultrasoun d evaluations to understand better the etiology of ovarian dysfunction so t hat effective treatments can be developed to induce consistent ovarian acti vity. Zoo BioI 18:223232, 1999. (C) 1999 Wiley-Liss, Inc.