Daily Treatment with Human Recombinant Parathyroid Hormone-(1–34), LY333334, for 1 Year Increases Bone Mass in Ovariectomized Monkeys*

PTH stimulates bone formation to increase bone mass and strength in rats and humans. The aim of this study was to determine the skeletal effects of recombinant human PTH-(1–34) [rhPTH-(1–34)] in monkeys, as monkey bone remodeling and structure are similar to those in human bone. Adult female cynomolgus monkeys were divided into sham-vehicle (n= 21), ovariectomized (OVX)-vehicle (n = 20), and OVX groups given daily sc injections of rhPTH-(1–34) at 1 (n = 39) or 5 (n = 41) μg/kg for 12 months. Whole body bone mineral content was measured, as was bone mineral density (BMD) in the spine, proximal tibia, midshaft radius, and distal radius. Serum and urine samples were also analyzed. rhPTH-(1–34) treatment did not influence serum ionized Ca levels or urinary Ca excretion, but depressed endogenous PTH while increasing serum calcitriol levels. Compared to that in the OVX group, the higher dose of rhPTH-(1–34) increased spine BMD by 14.3%, whole body bone mineral content by 8.6%, and proximal tibia BMD by 10.8%. Subregion analyses suggested that the anabolic effect of rhPTH-(1–34) on the proximal tibia was primarily in cancellous bone. Similar, but less dramatic, effects on BMD were observed with the lower dose of rhPTH-(1–34). Daily sc rhPTH-(1–34) treatment for 1 yr increases BMD in ovariectomized monkeys without inducing sustained hypercalcemia or hypercalciuria.