A COMPARISON OF THE EFFECT OF SYNTHETIC AND MICRONIZED HORMONE REPLACEMENT THERAPY ON BONE-MINERAL DENSITY AND BIOCHEMICAL MARKERS OF BONE METABOLISM

In this prospective study, the relationship between biochemical marker s of bone turnover and changes in bone mass of the lumbar spine and pr oximal femur were evaluated. Thirty-two postmenopausal women were rand omly assigned to either conjugated equine estrogen (0.625 mg) and medr oxyprogesterone acetate (5.0 mg, synthetic E/P, n = 15) or micronized 17-beta estradiol (1.0 mg) and micronized progesterone (200 mg, micron ized E/P, n = 17) administered daily and continuously for 13 cycles. D emographic and baseline hormonal profiles did not differ (p > 0.05) be tween the groups. Osteocalcin, bone-specific alkaline phosphatase, typ e I procollagen peptide, and cross-linked N-terminal telopeptide of ty pe I collagen were measured in both serum and urine, and bone mineral density was assessed prior to and after the 13-cycle treatment period. Lumbar (L2-L4) bone density improved (p < 0.01) by 5.0% and 3.8% in b oth the synthetic E/P and micronized E/P groups, respectively. Proxima l femur bone density improved by 2.6% (p < 0.05) and 3.1% (p < 0.01) i n the synthetic and micronized E/P groups, respectively. Overall, mark ers of bone turnover decreased 18-47% in both treatment groups (p < 0. 01). Specifically, markers of formation decreased: serum osteocalcin b y 46.8% and 19.5%, bone-specific alkaline phosphatase by 42.9% and 18. 9%, and type I procollagen peptide by 25.8% and 29.0% in the synthetic E/P and micronized E/P groups, respectively. Rates of bone resorption , as determined by cross-linked N-terminal telopeptide of type I colla gen levels, were reduced by 46.4% and 43.4% in the synthetic E/P and m icronized E/P groups, respectively. Among the markers, baseline values for type I collagen peptide were correlated with changes in bone mine ral density at the lumbar spine (r = 0.399, p < 0.026) and proximal fe mur (r = 0.387, p < 0.05). The percent change from baseline levels of type I collagen peptide was correlated (r = 0.381, p < 0.035) with cha nge in bone mineral density at the proximal femur only. These data sug gest that postmenopausal women with high bone turnover rates, as indic ated by increased type I procollagen peptide levels, may be more sensi tive to HRT as demonstrated by increased bone mineral density of the l umbar spine and proximal femur. Moreover, hormonal preparation does no t appear to have differential effects on markers of bone metabolism an d bone mass.