Use of the progestin challenge test in nonhuman primates ( Macaca fascicularis)

Abstract

Objective: To determine whether the progestin challenge test (PCT) would provide a reliable, noninvasive indicator of endometrial stimulation in nonhuman primates. Design: Randomized, 2×2, crossover study. Setting: Nonhuman primates ( Macaca fascicularis) in an academic research environment. Patient(s): Adult, surgically postmenopausal, female cynomolgous macaques (n = 27) were studied. Intervention(s): Females were randomly assigned to receive estradiol (n = 14; 0.028 mg/kg body weight) or vehicle (n = 13) daily. All animals were administered two PCTs in a crossover study design using two doses (0.28 mg/kg or 0.56 mg/kg body weight) of medroxyprogesterone acetate (MPA). Main Outcome Measure(s): Incidence and severity of withdrawal bleeding and serum estradiol (E 2) and progesterone (P 4) levels were evaluated. Result(s): Estradiol treatment resulted in endometrial “withdrawal” bleeding in all but one instance. Females receiving daily doses of E 2 exhibited a significantly greater ( P<.01) incidence, severity, and duration of withdrawal bleeding compared to control animals. Of the five positive responses observed in the control females, four occurred when the higher dose of MPA was administered. Conclusion(s): These results indicate that the PCT is a useful, noninvasive method for determining the presence of endometrial stimulation in nonhuman primates.