Review Question - QID 831

Treatment of osteoporosis centers on increasing bone mass by direct anabolic effect and/or inhibiting osteoclastic absorption. Bisphosphonates, selective estrogen receptor modulators, and calcitonin act to decrease bone resorption by inhibiting osteoclasts.

Parathyroid hormone causes both bone formation and resorption, depending on frequency of dosing. Osteoblasts are primary targets for PTH. Once activated, they secrete RANKL and IL-6, which causes osteoclast proliferation/maturation, leading to increased bone resorption. Because of this coupled remodeling process, several observations have been made: 1)intermittent PTH injections increase bone mass, 2) continous infusion lead to bone resorption, and 3) dosing should not continue past 2 yrs. Thus, intermittent parathyroid hormone is anabolic to bone and is used as a treatment of osteoporosis (forteo).