Context: Serum 25-hydroxyvitamin D (25OHD) concentrations > 30 ng/ml have been recommended for lowering fracture risk.

Objectives: To determine if 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 teriparatide was assessed in women subgrouped by having 25OHD insufficiency (> 10 but 30 ng/ml) or 25OHD sufficiency (> 30 but 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 to 1200 IU) daily, women were randomized to placebo, TPTD 20 µg or TPTD 40 µg by daily subcutaneous injection for a median of 19 months. Observation was for a median of 21 months.

Main Outcome Measures: Vertebral and nonvertebral fractures, change in bone mineral density (BMD) at the lumbar spine and femoral neck, change in bone formation marker amino-terminal extension peptide of procollagen type 1 (PINP), and the proportion of women with serum calcium 2.76 mmol/L 4 to 6 hours after dosing.

Results: TPTD reduced vertebral and nonvertebral fracture risk, increased lumbar spine and femoral neck BMD, and increased PINP 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.