Marker of Bone Resorption in Acute Response to Exogenous or Endogenous Parathyroid Hormone

Parathyroid hormone (PTH) changes morphology of osteoclasts within minutes after its systemic administration. The aim of our study was to test in healthy men whether both exogenous and endogenous PTH could change acutely (minutes to hours) the serum cross-linked C-telopeptide of type I collagen (beta CTX), which is released during osteoclastic resorption of bone. Twelve healthy men (age range 24-34 yr) were each studied during 180 min on a control period, after a single subcutaneous injection of teriparatide, and after 30 min EDTA infusion to stimulate endogenous PTH secretion. The tests were started after overnight fast, 3 h after a standard calcium load. The EDTA infusion induced a significant decrease in serum ionized calcium (by 8.5% at 33 min) and a significant increase in plasma PTH (by 305% at 33 min). Both the EDTA and teriparatide resulted in a significant increase in beta CTX (p < 0.001) with maximum increases of 64% and 80%, respectively. A mild, but significant decrease in beta CTX was observed during the control test period. In conclusion, single-dose teriparatide injection as well as a stimulation of endogenous PTH in healthy men results in an acute increase of the bone resorption marker.