Hypoestrogenic “inactive phases” at the start of the menstrual cycle: changes with age and reproductive stage, and relationship to follicular depletion

Follicular depletion models alone do not explain the observed pattern of IPs. Our data suggest that IPs reflect both follicular depletion and hyperstimulation in premenopausal and perimenopausal women. Knowledge of underlying IP patterns in the menstrual cycle could inform decisions about hormone sampling and contraception during the perimenopause.