Abstract: A pharmaceutical composition for oral administration comprising PTH, wherein the in vitro release of PTH-when tested in a dissolution test of pharmacopoeia standard-is delayed with at least 2 hours and once the release starts, at least 90% w/w such as, e.g., at least 95% or at least 99% of all PTH contained in the composition is released within at the most 2 hours. The composition may also comprises a calcium containing compound and/or a vitamin, D. In particular, PTH is administered in combination with a calcium-containing compound for the treatment or prevention of bone-related diseases, so that I) an effective amount of a calcium-containing compound is administered to lower the plasma level of endogenous PTH, and II) an effective amount of PTH is administered to obtain a peak concentration of Pm once the endogeneous PTH level is lowered. This present a potential therapeutic or prophylactic regimen for bone-related disorders including osteoporosis.