The purpose of this study is to examine the effect of PTH(1-84) treatment over 24 months followed by 12 months discontinuation on BMD, bone turnover markers, fractures and the impact of adherence on efficacy.
Introduction: There is limited information about the effect of PTH(1-84) after 18 months and limited data about the impact of compliance on response to anabolic therapy.
Methods: Seven hundred and eighty-one subjects who received active PTH(1-84) in the Treatment of Osteoporosis with Parathyroid hormone trial for approximately 18 months were entered into a 6-month open-label extension. Thereafter, they were followed for 12 additional months after discontinuation of treatment. Endpoints examined included changes in BMD and biochemical markers.
Results: PTH(1-84) treatment over 24 months increased BMD at the lumbar spine by 6.8% above baseline (p<0.05).The total corresponding BMD increases at the hip and femoral neck were 1.1 and 2.2% above baseline. Larger increases in spine BMD were observed in participants with ≥80% adherence to daily injections of PTH(1-84) (8.3% in adherent vs 4.9% in poorly adherent patients). Total hip BMD gains were 1.7% in adherent vs 0.6% in poorly adherent participants. Markers of bone turnover (BSAP and NTx) peaked 6 months after starting PTH(1-84) treatment and declined slowly but remained above baseline at 24 months. After discontinuation of PTH(1-84) treatment (at 24 months), bone turnover markers returned to near baseline levels by 30 months. The adherent group sustained significantly fewer fractures than the poorly adherent group.
Conclusions: PTH(1-84) treatment over 24 months results in continued increases in lumbar spine BMD. Adherence to treatment with PTH(1-84) for up to 24 months is also associated with greater efficacy.