Lumbar bone mineral density in very long-term renal transplant recipients: impact of circulating sex hormones.

The influence of circulating sex hormones and gender on the bone mineral density (BMD) in long-term renal transplant recipients needs further investigation. We performed a retrospective analysis of lumbar BMD between 6 years and 20 years after renal transplantation. In 67 patients (47+/-12 years, 38 male) with a minimum interval of 72 months after transplantation, lumbar BMD measurements (dual energy X-ray absorptiometry) were performed (=complete cohort). Thirty-one patients (=longitudinal cohort) underwent at least three serial BMD measurements (mean follow-up 39+/-18 months, start at 86+/-22 months). All patients received prednisolone. In the complete cohort, BMD was significantly reduced in comparison to young healthy (mean T-score -1.33+/-1.40) and age-matched controls (mean Z-score -0.91+/-1.45) at 88+/-31 months (p<0.05). Osteopenia or osteoporosis were present in two-thirds of patients. In the longitudinal cohort, a mean annual lumbar BMD loss of -0.6+/-1.9% was detectable equivalent to a -0.03+/-0.15 reduction of Z-scores per year (regression analysis). Impact of hormonal status: In the complete cohort, postmenopausal status was associated with significantly lower BMD levels compared to men (p=0.0441). Women and men within the lowest tertile of sex hormone levels (LH, FSH, DHEAS, testosterone, progesterone, estradiol) did not exhibit significant differences in terms of lumbar BMD compared to those in the highest tertile. The mean annual bone loss was statistically indistinguishable between men and women. There was no significant correlation of sex hormone levels and BMD in men and premenopausal women. In postmenopausal women, however, low estradiol and high LH levels correlated with the extent of annual BMD loss (p<0.05). Our data confirm significantly reduced lumbar T-scores in the very late period after renal transplantation. The lumbar BMD decreased by -0.6+/-1.9% per year. In postmenopausal long-term renal transplant recipients, low estradiol levels were associated with accelerated bone loss.