Objective: To determine whether the progestin challenge test (PCT) would provide a reliable, noninvasive indicator of endometrial stimulation in nonhuman primates. DESIGN; Randomized, 2x2, 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.