Use of leuprolide to treat endometriosis in a rhesus macaque

Endometriosis was diagnosed in an aged dysmenorrheic rhesus monkey (Macaca mulatta) after biopsy of a 7 cm abdominal mass which could not be completely resected due to extensive adhesions. A 6-month course of treatment with leuprolide, a gonadotropin-releasing hormone agonist, resulted in cessation of menstrual cycles and marked clinical improvement. Dysmenorrhea and hypovolemic shock occurred 2 months after therapy was completed. Despite supportive treatment and resumption of leuprolide, the primate's clinical deterioration and abdominal mass enlargement necessitated euthanasia. To our knowledge, this is the first report of a case of endometriosis in a rhesus macaque treated with a gonadotropin-releasing hormone agonist. Although prolonged leuprolide therapy was clinically effective, its cost and the difficulty in early diagnosis of endometriosis may limit its use in nonhuman primate medicine.