PTH and hyperparathyroidism: This results in improved bone mass and microarchitecture.(6, 7) Nevertheless, patients show greater osteoanabolic effects of PTH (1–34) in the first 1–2 years of treatment, which is then taken over by an increase in bone resorption, creating what some have called “the anabolic window.”(7, 8, 9, 10) On the other hand, the balance is negative with continuous infusion of PTH (1–34) or elevated PTH levels in hyperparathyroidism.