[Androgen function on skeletal tissues: analysis of androgen receptor-deficient mice]

Although sex hormones had been thought to be essential for normal skeletal development and maintenance of bone mass, the physiological role of androgen receptor (AR) in skeletal tissues was not well established. To reveal physiological function of AR on skeletal tissues, we generated AR deficient mice (AR KO) by means of the Cre-loxP system that was used to avoid the problem of male infertility and analyzed their phenotype in skeletal tissues. It was indicated that AR contributes to maintain bone mass in male, but not in female in mice. However, recent studies suggested the contribution of sex hormones to maintain bone mass is different not only between sexes but among species due to the difference of aromatase activity.