An open label 12-month pilot trial on the effects of the aromatase inhibitor anastrozole in growth hormone (GH)-treated GH deficient adolescent boys.

Objective: To investigate whether 12 mo treatment with the aromatase inhibitor anastrozole can achieve sustained suppression of estrogen production and delay epiphyseal fusion in growth hormone deficient (GHD) adolescent males.

Study Design: 20 adolescents with GHD were recruited (mean age +/- SE: 14.7 +/- 0.5 yr). Ten continued on GH (control group), and 10 on GH and anastrozole (Rx group) for 12 mo.

Results: After 12 mo E2 concentrations declined 60% in the Rx group (from 1.8 +/- 0.5 to 0.7 +/- 0.3 pg/ml, p <0.05) whereas they increased in controls (from 1.2 +/- 0.7 to 1.8 +/- 0.7, p <0.05). Testosterone increased 117% in the Rx group (from 304 +/- 31 to 626 +/- 64 ng/dl), 47% in controls (from 274 +/- 89 to 398 +/- 51) (p = 0.03, ANOVA between groups). IGF-I increased 42% in controls (454 +/- 22 to 711 +/- 109 ng/ml, p <0.05), but remained invariant in the Rx group (446 +/- 29 to 540 +/- 80, p = NS). Bone markers, plasma lipids, insulin, glucose, and liver function tests were all unchanged between groups with no differences either in body composition or bone mineral density accrual. There were no differences in growth velocity, height SDS, bone age advancement, predicted adult height or testicular volumes between groups after 12 mo.

Conclusions: Anastrozole treatment potently decreases estrogen concentrations in adolescent males with GHD while allowing normal virilization, without deleterious effects on body composition, plasma lipids, bone metabolism or the tempo of puberty. Twelve months of treatment, however, did not increase predicted adult height. Further studies are needed to ascertain whether more prolonged estrogen blockade is helpful in the treatment of growth retardation in puberty.