The effects of estrogen administration on bone mineral density in adolescents with anorexia nervosa

Profound osteopenia is a serious complication of anorexia nervosa (AN). The aim of this work was to study the effect of prolonged AN on lumbar spine bone mineral density (BMD) and to determine whether oral estrogen administration prevents bone loss in women with this disorder.

Thirty-eight amenorrheic women with AN (mean age: 17.3 years) were treated with estrogen (50 microg of ethinyl estradiol) and gestagen (0.5 mg of norgestrel) during 1 year. Clinical variations, biochemical indices and BMD were studied at three different time points, including after a period of amenorrhea of at least 12 months (n=38), after the administration of estrogens for 1 year (n=22), and after a 1-year follow-up period (n=12).

Initial mean BMD was significantly lower than normal (-2.1+/-0.8 s.d.) and less than -2.5 s.d. below normal in 38% of the women with AN. The estrogen-treated group had no significant change in BMD even after the follow-up period and partial recovery of weight. Estradiol and total IGF-I levels were significantly lower throughout the study. All subjects had normal thyroxine (T(4)) and TSH levels and calcium metabolism. However, total tri-iodothyronine (T(3)) was decreased in all anorexic subjects in the first and second study points and were within normal limits after the follow-up period.

(1) Estrogen replacement alone cannot prevent progressive osteopenia in young women with AN. (2) Other factors, such as the loss of weight, the duration of the amenorrhea and the low levels of total insulin-like growth factor-I (IGF-I) could contribute to the loss of bone mass in women with this disorder.