Treatment with the aromatase inhibitor letrozole during adolescence increases near-final height in boys with constitutional delay of puberty

Objective We investigated whether inhibition of oestrogen biosynthesis with the aromatase inhibitor, letrozole, during adolescence improves near-final height in boys with constitutional delay of puberty. Patients and methods Seventeen boys with constitutional delay of puberty were randomized to receive testosterone (T) enanthate (1 mg/kg i.m.) every 4 weeks for 6 months in combination with placebo (Pl, n = 8), or the aromatase inhibitor letrozole (Lz, 2(.)5 mg/day orally) (n = 9), for 12 months. After treatment, patients were followed up until near-final height. Height discrepancy was calculated as near-final height minus mid-parental target height. Measurements The primary end point was the difference in near-final height between the groups treated either with T + Pl or T + Lz. Secondarily, height discrepancy and gain in height standard deviation score (SDS) were analysed in both groups. Results Boys treated with T + Lz reached a higher mean near-final height than did boys on T + Pl (175(.)8 vs. 169(.)1 cm, respectively, P = 0(.)04). In T + Lz-treated boys, mean near-final height did not differ from their mid-parental target height (175(.)8 vs. 177(.)1 cm, P = 0(.)38), whereas in T + Pl-treated boys, mean near-final height was lower than mid-parental target height (169(.)1 vs. 173(.)9 cm, P = 0(.)007). T + Lz-treated boys had a greater increment in height SDS over the pretreatment height SDS than T + Pl-treated boys (+1(.)4 SDS vs. +0(.)8 SDS, P = 0(.)03). Conclusions Our findings indicate that in adolescent boys an increase in adult height can be attained by use of aromatase inhibitors.