We used dual energy X-ray absorptiometry (DXA) to study changes in estimated volumetric bone mineral density (EstVBMD) of the lumbar spine after gastrectomy. The study group comprised 41 men and 32 women. When EstVBMD was compared according to sex among patients younger than 60 years of age, patients 60 to 69 years of age, and patients these three groups in men (0.185 g/cm_3, 0.187 g/cm_3, 0.187 g/cm_3, respectively). In contrast , EstVBMD was significantly lower in women 60 to 69 years of age (0.157 g/cm_3) and those 70 years of age or older (0.159 g/cm_3) than in women younger than 60 years (0.200 g/cm_3) (P<0.01). When the relation between EstVBMD and the number of months after gastrectomy was studied according to sex in patients younger than 70 years, EstVBMD negatively correlated with the interval after operation in men (r= -0.365, P<0.05), whereas ther e was no correlation between these variables in women. These results suggest that after gastrectomy bone mineral density decreases gradually in men younger than 70 years, but not in women. The lack of a consistent change in bone mineral density after gastrectomy in women is apparently caused by the marked effect on bone metabolism of decreased female hormone levels after menopause.胃切除後の腰椎の骨密度の変化を dual energy X-ray absorptiornetory （DXA） 法で測定し, 単位体積当たりの計測値（Estimated volumetric bone mineral density: EstVBMD）を求めることにより検討した. 男女別に60歳未満, 60歳代, 70歳以上の群で比較すると, 男性では 0.185 g/cm_3, 0.187 g/cm_3, 0.187 g/cm_3と大差がなかった. 一方, 女性では 0.200 g/cm_3, 0.157 g/cm_3, 0.159 g/cm_3 と60歳未満の症例と比較し60歳代, 70歳以上の症例では減少し有意差を認めた. 70歳未満の症例で男女別に術後月数と骨密度との関係をみると, 男性では経過期間とともに骨密度は減少し, 負の相関関係 （r= -0.365, P<0.05）が認められたが, 女性では両者は独立した関係であった. 70歳未満の男性では胃切術後に徐々に骨塩量が低下するが, 女性では閉経後の女性ホルモン減少が強く骨代謝に現れるため胃切術後の影響が個々で異なることが示唆された
