Guest Author - Denise Howard, M.D., M.P.H.

Osteoporosis occurs when the bone density falls to a point that there is an increased risk of fracture with minimal trauma. The risk of developing osteoporosis is determined by the peak bone density achieved during childhood and the rate of bone loss later in life. Bone strength is due to the density of the bone but also bone quality. Bone density is easier to measure and therefore discussed more. In order to understand osteoporosis it is first important to understand how normal bone is maintained.

Healthy bone is maintained by a balance between the destruction of old, damaged bone and the formation of new bone. Cells called “osteoclasts” remove old bone by producing substances that destroy the old bone. Cells called “osteoblasts” secretes new bone matrix into the cavity where the old bone was removed. This process of bone resorption and formation, called remodeling, is the mechanism by which the skeleton maintains its strength.

An individual continues to build bone during childhood and adulthood. The maximum achieved bone mass is complete by age 40, however childhood bone development is the most crucial. The peak bone mass achieved is determined by environmental and genetic factors.

Bone loss occurs because of an imbalance between the activity of the osteoclasts and osteoblasts. Postmenopausal women develop significantly increased bone turnover, which continues for many years after the cessation of ovarian function. This is due to a decrease in estrogen production. This loss of estrogen leads to an increase in the life span of the osteoclasts (cells that destroy bone) and a shortening of the life span of the osteoblasts (cells that make new bone).

Understanding how bone works leads to a better understanding of risk factors for developing low bone density and osteoporosis. As mentioned earlier bone density is determined by peak bone mass achieved and increased bone turnover. Menopause and early menopause are major risk factors due to the increased bone turnover that occurs once estrogen production stops. Caucasian women are at increased risk because of a lower peak bone mass achieved when compared to women of other racial groups. Smoking and excessive alcohol use leads to increased bone loss. Other factors that contribute to an increased risk of osteoporosis include certain medications, certain medical conditions, vitamin D deficiency and poor calcium absorption.

Understanding risk for osteoporosis is helpful in targeting prevention and early diagnosis. The overall goal is fracture prevention which is the cause of excessive morbidity and mortality. Current mechanisms for prevention and treatment are effective but there are many people who are unaware of their risks and many healthcare providers who do not discuss this problem. As with many disorders, prevention and early intervention is the key to minimize poor outcomes.