Response to Teriparatide in Patients with Baseline 25-Hydroxyvitamin D Insufficiency or Sufficiency

Abstract

Serum 25-hydroxyvitamin D (25OHD) concentrations greater than 30 ng/ml have been recommended for lowering fracture risk. Our objective was to determine whether 25OHD sufficiency is a prerequisite for effective response to teriparatide (TPTD). 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. 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 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. 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. 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.