The high-affinity estrogen receptor antagonist ICI 182,780 has no effect on bone growth in young male rats

Estrogens have profound effects on the processes of bone formation and turnover in females. The physiological role of this class of hormones on bone metabolism in males is less certain. The purpose of this study was to determine the effect of the high affinity estrogen receptor antagonist ICI 182,780 on tibial growth in normal male rats. The effects of ICI 182,780 on growing male rats were compared to orchiectomy, which prevents the synthesis of estrogens as well as androgens. Neither orchiectomy nor ICI 182,780 had an effect on body weight gained. Orchiectomy decreased longitudinal bone growth at the proximal tibial metaphysis and radial bone growth at the tibia-fibula synostosis. In contrast, ICI 182,780 had no effect on either endochondral or intramembranous bone growth. These findings suggest that androgens are more important than estrogens in determining peak bone mass in male rats.