Hero M et al. (2006) Treatment with the aromatase inhibitor letrozole during adolescence increases near-final height in boys with constitutional delay of puberty. Clin Endocrinol 64: 510–513

Aromatase inhibitors are able to block the biosynthesis of estrogen—a process that is essential in bone maturation, growth-plate fusion, and cessation of longitudinal growth. Aromatase inhibitors might, therefore, be used therapeutically to increase adult height.

In a Finnish study by Hero et al., 17 boys with constitutional delay of puberty randomly received either testosterone with placebo, or testosterone with the aromatase inhibitor letrozole, for 12 months. Patients were then followed up until they reached near-final height (i.e. their height at a bone age ≥15.75 years). Boys treated with testosterone and placebo reached a mean near-final height of 169.1 cm, compared with 175.8 cm in boys treated with testosterone and letrozole. During treatment, boys in the letrozole group had lower estradiol and higher gonadotrophin concentrations than those in the placebo group. The near-final height of boys in the placebo group was less than their midparental target height; however, this difference was not observed in boys in the letrozole group.

The authors conclude that aromatase inhibitors are a promising tool to improve final adult height in boys with constitutional delay of puberty. Larger studies are needed to confirm the efficacy of aromatase inhibitors in patients with growth disorders, and to investigate the effects of these inhibitors on bone health, maturing spermatogenesis, and carbohydrate and lipid function.