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

Clin Endocrinol (Oxf). 2006 May;64(5):510-3. doi: 10.1111/j.1365-2265.2006.02499.x.


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.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Aromatase Inhibitors / therapeutic use*
  • Body Height / drug effects*
  • Estradiol / blood
  • Follicle Stimulating Hormone / blood
  • Humans
  • Letrozole
  • Luteinizing Hormone / blood
  • Male
  • Nitriles / therapeutic use*
  • Prospective Studies
  • Puberty, Delayed / blood
  • Puberty, Delayed / drug therapy*
  • Testosterone / blood
  • Time Factors
  • Triazoles / therapeutic use*


  • Aromatase Inhibitors
  • Nitriles
  • Triazoles
  • Testosterone
  • Estradiol
  • Letrozole
  • Luteinizing Hormone
  • Follicle Stimulating Hormone