Context: Precocious puberty (PP) in girls with McCune-Albright syndrome (MAS) is characterized by episodic development of large unilateral ovarian cysts followed by sudden onset of vaginal bleeding. Some patients experience frequent bleeding as well as accelerated linear growth and advanced skeletal maturation. The use of anastrozole for the treatment of PP in this condition has not been well studied.

Objective: To determine the safety and efficacy of the aromatase inhibitor anastrozole for the treatment of PP in girls with MAS.

Design and Settings: A prospective international multicenter study in which subjects received anastrozole 1 mg daily for one year.

Patients: Twenty eight girls 10 years of age with MAS and progressive PP were enrolled.

Main outcome measures: Vaginal bleeding, rate of skeletal maturation (BA/CA), growth velocity, and uterine/ovarian volumes. These indices were compared to a 6 month pretreatment interval.

Results: No difference in vaginal bleeding (mean # days/yr) was noted. Mean change in BA/CA, which was 1.25 ± 0.77 at baseline, was -0.25 ± 1.02 at study end (p=0.22). Average growth velocity z score was 1.40 ± 3.15 at study entry and was 0.26 ± 2.71 at 12 months (p=0.10). Mean ovarian/uterine volumes were unaffected by anastrozole, and no significant adverse events occurred.

Conclusions: Although it appears safe, anastrozole for one year was ineffective in halting vaginal bleeding, attenuating rates of skeletal maturation and linear growth in girls with MAS. Pharmacologic strategies other than anastrozole should be pursued for the treatment of PP in this population.