Review Question - QID 3213

Teriparatide (Forteo) comprises the first 34 amino acids of the 84 amino acid parathyroid hormone(PTH) and can reproduce the primary effects of PTH by activating adenyl cyclase. The review article by Barnes et al describes PTH as the primary regulator of calcium and phosphate metabolism in bone and kidney. Intermittent PTH treatment increases bone mineral density by increasing coupled remodeling between osteoclast-mediated bone resorption and osteoblast-mediated new bone formation. Continuous dosing would stimulate bone resorption. Thus, an intermittent dosing in the form of daily injections of teriparatide have a net effect of stimulating new bone formation. The Level 1 study by Neer et al found that daily treatment with parathyroid hormone (1-34) reduced the risk of nonvertebral fractures by 35 percent at the 20-µg dose and by 40 percent at the 40-µg dose and reduced the risk of nonvertebral fragility fractures by 53 and 54 percent, respectively. Risedronate(Actonel), alendronate(Fosamax), ibandronate(Boniva), and zoledronic acid (Reclast) are nitrogen containing bisphosphonates that inhibit osteoclast resorption by inhibiting the enzyme farnesyl diphosphate synthase.