CHARACTERIZATION OF THE ONSET OF MENOPAUSE IN THE RHESUS MACAQUE

The objective of this study was to assess ovarian activity in a cohort of aged female rhesus macaques. Menstrual records for 26 rhesus macaq ues ages 20-29 yr were evaluated over a 1-yr period, and daily urinary estrone conjugate (E1C) and pregnanediol-3-glucuronide (Hygeia [Hy]-P dG) levers were determined for 12 wk. Each animal was categorized as e ither pre-, peri-, or postmenopausal based on menstrual and hormonal d ata. Eleven animals (mean age 22.5 yr) were premenopausal, thirteen (m ean age 24 yr) were perimenopausal, and two (mean age 29.5 yr) were po stmenopausal. Hormone profiles for perimenopausal animals reveal prolo nged follicular phases and/or a lack of patterned Hy-PdG dynamics. Bre akthrough bleeding occurred in four of these perimenopausal animals. T he postmenopausal animals were amenorrheic and exhibited low E1C level s (less than 10 ng/mg creatinine). The results of this study illustrat e that the decline of ovarian function in female macaques during the t hird decade of life parallels the menstrual and hormonal events associ ated with the climacteric in women, and that menopause does occur in r hesus macaques.