Hi gigi4, most of literature I've read states that as women age and go through menopause there is less estrogen produced. Estrogen is like a gate keeper controlling certain bodily systems. So when there is low estrogen its more difficult for you body manage these systems. I'm not an expert and recommend a couple good books to read are Mayo Clinic on Osteoporoisis book by Anne E. Kearns, MD, PhD. and Great Bones by R. Keith McCormick.