Menstrual cycles, lifespan, and anti-Müllerian hormone in cynomolgus monkeys

The cynomolgus monkey (Macaca fascicularis) is an important experimental animal; however, its menstrual patterns, lifespan, and age-related changes in anti-Müllerian hormone (AMH) levels remain poorly characterized. This study aimed to analyze these factors and evaluate the usefulness of Cynomolgus monkeys in ovarian function research. The age at menarche was examined in 21 cynomolgus monkeys, and the age at menopause and age at death were tracked in another 22 postmenopausal monkeys. In addition, AMH levels were analyzed in 74 cynomolgus monkeys aged 0 to 33 years to evaluate ovarian reserve throughout their lives. Results showed a mean age at menarche of 3.69 ± 2.51 years, menopause at 27.00 ± 2.50 years, and a mean age at death of 32.04 ± 5.33 years. AMH levels throughout life showed a weak negative correlation with age. These findings suggest that changes in ovarian reserve throughout the life span of cynomolgus monkeys are similar to those in humans. To our knowledge, this study is the first to analyze menstruation, lifespan, and lifelong AMH levels in cynomolgus monkeys. Ovarian function throughout life, including childhood and postmenopause, was similar to that in humans, suggesting cynomolgus monkeys may be a useful experimental model.