Secondary hyperparathyroidism due to hypovitaminosis D affects bone mineral density response to alendronate in elderly women with osteoporosis: a randomized controlled trial

OBJECTIVES: To determine whether secondary hyperparathyroidism (HPTH) due to hypovitaminosis D affects bone mineral density (BMD) response to alendronate (ALN) in elderly women with osteoporosis.

DESIGN: Randomized, controlled trial with 1-year follow-up.

SETTING: Two osteoporosis centers in northern Italy.

PARTICIPANTS: Community-dwelling women aged 60 and older with a BMD T-score below -2.5 and secondary HPTH with vitamin D insufficiency.

INTERVENTION: One hundred twenty subjects were randomly assigned to receive ALN 70 mg once a week alone or ALN 70 mg once a week plus calcitriol (1,25D3) 0.5 microg daily.

MEASUREMENTS: BMD measured using dual-energy x-ray absorptiometry at the lumbar spine (L1-L4), femoral neck, and total hip and serum levels of intact PTH at baseline and 12 months.

RESULTS: After 1 year, BMD of the lumbar spine, femoral neck, and total hip significantly increased from baseline in both groups (P<.001). Patients allocated to ALN plus 1,25D3 demonstrated a significantly higher increase in lumbar spine BMD than those receiving ALN alone (mean percentage+/-standard deviation 6.8+/-4.6 vs 3.7+/-3.2, P<.001). Serum levels of PTH did not change significantly at 1 year in the ALN group (mean percentage, -3.7+/-27.1, P=.13) but decreased significantly in the ALN plus 1,25D3 group (-32.1+/-22.1, P<.001). At 12 months, subjects with normalized PTH independent of therapy allocation had a greater increase in lumbar spine BMD than those with persistent HPTH (6.5+/-4.6% vs 3.7+/-3.4%, P<.001). Lumbar spine BMD changes showed a significant negative correlation with PTH at 1 year (correlation coefficient (rho) =-0.399, P<.001) and a positive correlation with PTH changes (i.e., baseline value - 1 year value; rho=0.295, P=.005).

CONCLUSION: Persistence of secondary HPTH reduces BMD response to ALN in older women with osteoporosis.