Short-term changes in bone turnover markers and bone mineral density response to parathyroid hormone in postmenopausal women with osteoporosis.

CONTEXT

Treatment of osteoporotic women with PTH increases biochemical markers of bone turnover, increases axial bone mineral density (BMD), and reduces fracture risk.

OBJECTIVE

Our objective was to determine the relationship between levels of baseline turnover before PTH therapy and short-term changes in turnover during PTH therapy and subsequent changes in areal and volumetric BMD.

DESIGN AND SETTING

We conducted a randomized, placebo-controlled trial at four academic centers.

PATIENTS

Patients included 238 postmenopausal women with low hip or spine BMD.

INTERVENTION

Subjects were randomized to sc PTH (1-84), 100 mug/d (119 women), for 1 yr.

MAIN OUTCOME MEASURE

Bone turnover markers were measured in fasting blood samples collected before therapy and after 1 and 3 months. Areal and volumetric BMD at the spine and hip were assessed by dual-energy x-ray absorptiometry and quantitative computed tomography (QCT) after 1 yr of therapy.

RESULTS

Among women treated with PTH alone, the relationships between baseline turnover and 1-yr changes in dual-energy x-ray absorptiometry and QCT BMD were inconsistent. Greater 1- and 3-month increases in turnover, particularly the formation marker N-propeptide of type I collagen, were associated with greater increases in areal BMD. When volumetric hip and spine BMD were assessed by QCT, greater short-term increases in turnover were even more positively associated with 1-yr increases in BMD. Each sd increase in the 3-month change of N-propeptide of type I collagen was associated with an a 21% greater increase in QCT spine trabecular BMD.

CONCLUSIONS

Greater short-term changes in turnover with PTH therapy are associated with greater 1-yr increases in spine and hip BMD among postmenopausal osteoporotic women.