Context: Teriparatide (TPTD) [recombinant human PTH(1-34)] given sc once daily transiently increases serum calcium concentrations at 4-6 h after dosing, but its effects on urinary calcium excretion are less well studied.
Objective: Our objective was to evaluate urinary calcium excretion, a prespecified safety endpoint, for up to 12 months of TPTD treatment.
Design: This study included two prospective, randomized, double-blind placebo-controlled clinical trials.
Participants: A total of 2074 participants with osteoporosis or low bone mass (study 1, 1637 postmenopausal women; study 2, 437 men) were included.
Interventions: Participants were given calcium (1000 mg/d) and vitamin D (400-1200 IU/d) supplements, and were randomized to placebo, TPTD 20 mug/d, or TPTD 40 mug/d.
Main outcome measures: Urinary calcium excretion was measured in 24-h collections at baseline, 1, 6, and 12 months.
Results: In each study, baseline urinary calcium excretion was similar among groups. All groups had significantly increased urinary calcium excretion, compared with baseline, at most post-baseline time points. Post-baseline urinary calcium excretion was increased in the TPTD 20 microg/d group by up to 32 mg/d compared with placebo at the same time point (P < 0.05) in study 1. A total of seven participants (0.3%), of which three and four were in the placebo and TPTD groups, respectively, discontinued study drug due to repeated hypercalciuria (>300 mg/d).
Conclusion: Urinary calcium excretion was increased with TPTD treatment for up to 12 months, compared with placebo and baseline values, but the magnitude of these changes is unlikely to be clinically relevant or warrant urinary calcium monitoring for most patients.