CLINICAL OBSERVATIONS WITH A NEW SPECIFIC ASSAY FOR BONE ALKALINE-PHOSPHATASE - A CROSS-SECTIONAL STUDY IN OSTEOPOROTIC AND PAGETIC SUBJECTS AND LONGITUDINAL EVALUATION OF THE RESPONSE TO OVARIECTOMY, ESTROGENS, AND BISPHOSPHONATES

The purpose of this study was to examine the serum levels of bone alka line phosphatase (BALP) measured with a new assay in normal and in ost eoporotic women, and to evaluate prospectively its responsiveness to c hanges of bone metabolism. The following groups of subjects were studi ed: (1) 96 healthy women (44-75 years) (22 pre- and 73 postmenopausal) and 35 osteoporotic women [vertebral bone mineral density (BMD) more than 2.5 SD below the normal adult mean]; (2) 10 women (44-50 years) o variectomized (OVX) for benign uterine diseases, examined before and 1 2 months after surgery; (3) 16 OVX women (36-54 years), examined befor e and after 12 months of transdermal estrogen replacement therapy (50 mu g/day); (4) 12 previously untreated pagetic patients (4 women and 8 men, 50-80 years), examined before and and 3 months after the I.V. ad ministration of clodronate (600 mg) or alendronate (5 mg) for 2 consec utive days. The median BALP value was 11.6 U/liter 25-75th percentiles : 10.5-12.7; range 7.7-19.3) in healthy premenopausal (PreMP) women an d significantly higher (median: 16.8 U/liter; 25-75th percentile: 13.8 -21.8; P < 0.01) in postmenopausal (PostMP) women. There was a clear a ge-related increase in normal subjects (r = 0.43; P < 0.001). In the o steoporotic group, BALP levels, as well as other biochemical parameter s of bone turnover, were not significantly different from those of nor mal women when adjusted for age. In OVX women, BALP levels showed a ma rked increase 12 months after surgery (median: 113%: 25-75th percentil e: 87-139%), significantly higher than the increase of total ALP (medi an: 43%; 25-75th percentile: 25-66%; P < 0.001), and similar to the in creases of serum osteocalcin and urinary hydroxyproline. Transdermal e strogen treatment prevented the BALP increase, even if no reduction wa s observed; total ALP showed a similar behavior. The basal levels of B ALP were significantly elevated in pagetic patients (median: 91 U/lite r; rang 18-610 U/liter) and correlated to the scintigraphic extent of the disease (r = 0.76; P < 0.01). In conclusion, these results suggest that BALP measurement with this immunoassay may be clinically useful, and more sensitive than total ALP, in the assessment of bone turnover during changes of the estrogen status as well as in monitoring the ef fects of treatments that modify the metabolic activity of the skeleton .