Growth Hormone Plus Letrozole Boosts Final Height in Boys With Idiopathic Short Stature: ENDO 2026
USA: A combination of growth hormone (GH) and letrozole significantly increased adult height in adolescent boys with idiopathic short stature (ISS), according to research presented at ENDO 2026. The study found that the dual therapy improved final height by more than 5 cm beyond projected adult height, with no treatment-related adverse effects reported during follow-up.
The findings were presented by Victoria Leal from FUCS Pediatric Endocrinology, Bogotá, Colombia, during a poster session at the ENDO 2026.
Idiopathic short stature refers to significantly below-average height without an identifiable genetic, hormonal, or systemic cause. Treating adolescents with ISS can be challenging because the effectiveness of growth hormone therapy tends to decline as puberty progresses. Increasing levels of sex steroids accelerate skeletal maturation and can lead to earlier closure of growth plates, limiting the remaining growth potential.
Researchers evaluated whether combining growth hormone with letrozole, an aromatase inhibitor that reduces estrogen production, could help preserve growth potential and improve adult height outcomes in adolescent boys with ISS.
The study included 31 adolescent males with a bone age between 12 and 14 years and no detectable genetic or hormonal abnormalities. Participants received letrozole 2.5 mg daily along with growth hormone at a dose of 0.04 mg/kg/day. Patients were monitored every three months until they reached final height, defined as a bone age of 15 years or a growth velocity of less than 1 cm over six months.
At study entry, the participants had a mean age of 11.8 years and an average height of 146.2 cm. Their mean bone age was 12.6 years. Using the Bayley-Pinneau method, researchers estimated a projected adult height of 162.8 cm before treatment.
Key findings included:
- The mean final adult height achieved was 168.2 cm.
- Final height exceeded the projected adult height by an average of 5.4 cm.
- Treatment was administered for an average of 2.8 years.
- No adverse effects were reported during therapy.
The results suggest that delaying skeletal maturation while maintaining growth hormone stimulation may allow adolescents with ISS to achieve greater height gains than expected.
According to the investigators, the combined approach may be particularly beneficial for boys whose bone age has already advanced beyond 12 years, a stage at which conventional growth hormone therapy alone may offer more limited benefits.
The researchers concluded that growth hormone combined with letrozole substantially improved adult height outcomes in adolescent males with idiopathic short stature. Importantly, the treatment was well tolerated throughout the study period, with no safety concerns identified. Further studies involving larger patient populations and longer follow-up will help confirm the long-term efficacy and safety of this therapeutic strategy.
Next Story