Response to teriparatide in patients with baseline 25-hydroxyvitamin D insufficiency or sufficiency.

Context: Serum 25-hydroxyvitamin D (25OHD) concentrations greater than 30 ng/ml have been recommended for lowering fracture risk.
Objective: Our objective was to determine whether 25OHD sufficiency is a prerequisite for effective response to teriparatide (TPTD).
Design and Patients: Data were from 1620 osteoporotic postmenopausal women in the Fracture Prevention Trial. The response to TPTD was assessed in women subgrouped by having 25OHD insufficiency (>10 but <or=30 ng/ml) or 25OHD sufficiency (>30 but <or=183 ng/ml) at the baseline (randomization) visit. An abnormal intact PTH was exclusionary.
Interventions: At baseline, after at least 1 month of supplementation with calcium (1000 mg) and vitamin D (400-1200 IU) daily, women were randomized to placebo or 20 or 40 microg TPTD by daily sc injection for a median of 19 months. Observation was for a median of 21 months.
Main Outcome Measures: Main outcome measures included vertebral and nonvertebral fractures, change in bone mineral density at the lumbar spine and femoral neck, change in bone formation marker amino-terminal extension peptide of procollagen type 1, and the proportion of women with serum calcium at least 2.76 mmol/liter 4-6 h after dosing.
Results: TPTD reduced vertebral and nonvertebral fracture risk, increased lumbar spine and femoral neck bone mineral density, and increased amino-terminal extension peptide of procollagen type 1 relative to placebo in the two 25OHD subgroups. There were no significant differences in these endpoints between the subgroups (each treatment by subgroup interaction, P > 0.10). However, it should be noted that because of the limited number of fractures, this study does not exclude the possibility of differences in fracture outcome between the subgroups.
Conclusions: In postmenopausal women with osteoporosis and normal intact PTH, the responses to TPTD did not differ significantly in women with baseline 25OHD insufficiency or sufficiency.