T score of trabecular and cortical bone in normal postmenopausal women

The T score of the cortical and trabecular bone compartments (T score of BMDTrab and T score of BMDCorti) was calculated in healthy postmenopausal women to determine which bone compartment loses more bone mass.

A total 134 healthy postmenopausal women (mean age 55.1 +/- 6.4 years) and 67 healthy premenopausal women (mean age 36.0 +/- 8.6 years) were studied. Determinations were made using peripheral quantitative computed tomography (pQCT) of the nondominant forearm. The postmenopausal women were divided into groups by years since menopause (YSM): two early postmenopausal groups: < 5 YSM and 6-10 YSM; and two late postmenopausal groups: 11-20 YSM and > 20 YSM.

There was a significant correlation between the T score of BMDTrab and the T score of BMDCorti (P < 0.0001). Both correlated negatively and significantly with age (P < 0.001 and P < 0.0001, respectively) and neither correlated with weight. The Wilcoxon test showed no significant differences between the trabecular and cortical T scores in the overall group of women. By YSM, only the > 20 YSM group showed significant differences (P < 0.005). The ANOVA post hoc Bonferroni/Dunn test showed a significant difference in the T score of BMDTrab by YSM only in the < 5 YSM versus 11-20 YSM groups (P = 0.007) and in the < 5 YSM versus > 20 YSM groups (P < 0.0001). The T score of BMDCorti by YSM differed significantly only between the < 5 YSM versus 11-20 YSM groups (P < 0.0001) and between the 11-20 YSM and > 20 YSM groups (P < 0.005).

In contrast with what has been postulated in recent studies, our results showed that postmenopausal bone loss was similar in the cortical and trabecular bone compartments in the first 20 years after menopause. Trabecular bone loss was greater than cortical bone loss in late menopause (> 20 years).