PTH and hyperparathyroidism: We and others (5, 38) show that despite hyperparathyroidism, osteoclast number is reduced and active osteoclast surfaces are normal in Dmp1KO bones compared with WT, which suggests that low bone volume in Dmp1KO mice is not caused by increased bone resorption and that PTH plays a minimal role in the Dmp1KO bone phenotype.