Preliminary report of impaired oestrogen receptor-alpha expression in bone, but no involvement of androgen receptor, in male idiopathic osteoporosis

In western countries, osteoporosis affects at least 1 in 12 of all adult ma les and a third of osteoporotic men hale idiopathic disease (MIO). Both oes trogen and testosterone are now known to be important to the male skeleton, As normal oestrogen levels have been found in younger MIO cases, it is hyp othesized that, in bone, their responses to gonadal steroids may be defecti ve, through impaired receptor expression. This study therefore compared oes trogen receptor (ER)-alpha and androgen receptor (AR) expression, by indire ct immunofluorescence and semi-quantitative image analysis, in undecalcifie d fresh frozen bone sections from MIO patients (33-56 years), age-matched c ontrol men (n=7), and, for reference, ovarian steroid-replete (n=7) and -de ficient women (n=6). In normal men, 23% 6% osteoblasts and 14% +/- SEM 2% o steocytes expressed ER alpha protein, similar to hormone-replete women. Alt hough receptor expression decreased in hormone-deficient women, loss of ER alpha protein in MIO patients mas more severe (1%+/-SEM 0.5% osteocytes, 2% +/-SEM 1% osteoblasts expressed receptor). In all four groups, there,vas li ttle osteocyte AR expression, but in the women, a proportion of osteoblasts were receptor-positive. Deficient osteoblast and osteocyte ER alpha protei n expression could explain the bone loss in these MIO patients. Copyright ( C) 2000 John Wiley & Sons, Ltd.