Impaired body weight and tail length gain and altered bone quality after treatment with the aromatase inhibitor exemestane in male rats.

Background: Estrogen deficiency induced by aromatase inhibitors may be a novel treatment modality for growth enhancement in short children, but may have adverse effects on bone, brain and reproduction.

Aim: To assess growth effects and potential adverse effects of aromatase inhibition in male rats.

Methods: 26-day-old prepubertal rats received intramuscular injections with placebo or the aromatase inhibitor exemestane at a dose of 10, 30 or 100 mg/kg/week [E10, E30, E100(6)] for 6 weeks, completely covering the sexual maturation phase, or with 3 weeks E100 followed by 3 weeks placebo [E100(3)]. Growth parameters and histology of the testis, seminal vesicle and brain were analyzed. Bone architecture was studied with X-ray microtomography.

Results: Exemestane dose-dependently decreased body weight and tail length gain, as well as liver and seminal vesicle weights, but did not affect nose-anus length gain, growth plate width or radial growth. E100(6) decreased trabecular thickness (epiphysis and metaphysis) and number (metaphysis). Normal IGF-I levels and brain, testis and seminal vesicle morphology were observed. E100(3) resulted in decreased tail length gain only.

Conclusion: Exemestane treatment during sexual maturation did not augment linear growth in male rats, but caused impaired body weight and tail length gain and osteopenia.