The effects of the estrogen receptor blocker, Faslodex (ICI 182,780), on estrogen-accelerated bone maturation in mice

Sex steroids accelerate bone maturation, but it is believed that estrogen a ction is needed for terminal epiphyseal fusion. In this study, we investiga ted the effects of a new estrogen-blocking agent, Faslodex (ICI 182,780), o n estrogen-accelerated skeletal maturation in immature mica, On day-of-life 2 through 8, mice pups received either estradiol (5 mu g/100 g body weight ), Faslodex (100 mu g/100 g body weight), a combination of Faslode?i + estr adiol, or vehicle alone. Skeletal maturation was assessed with a scoring sy stem based on the size and appearance of epiphyseal plates in the forepaw a nd the lumbar spine. Estradiol caused acceleration of bone maturation in ou r mouse model (p < 0.05). Faslodex blocked the effect of estrogen, such tha t the mice receiving Faslodex + estradiol did not vary significantly from c ontrols. Faslodex may prove useful in the treatment of patients with diseas es causing rapid skeletal maturation, such as precocious puberty.