Randomized Trial of Aromatase Inhibitors, Growth Hormone, or Combination in Pubertal Boys with Idiopathic, Short Stature

CONTEXT: Growth of short children in puberty is limited by the effect of estrogen on epiphyseal fusion. OBJECTIVES: To compare: 1) the efficacy and safety of aromatase inhibitors (AIs) vs GH vs AI/GH on increasing adult height potential in pubertal boys with severe idiopathic short stature (ISS); and 2) differences in body composition among groups. DESIGN: Randomized three-arm open-label comparator. SETTING: Outpatient clinical research. PATIENTS: Seventy-six pubertal boys mean (SE) age, 14.1 (0.1) years with ISS height SD score (SDS), -2.3 (0.0). INTERVENTION: Daily AIs (anastrozole or letrozole), GH, or AI/GH for 24-36 months. OUTCOMES: Anthropometry, bone ages, dual x-ray absorptiometry, spine x-rays, hormones, safety labs. RESULTS: Height gain mean (SE) at 24 months was: AI, +14.0 (0.8) cm; GH, +17.1 (0.9) cm; AI/GH, +18.9 (0.8) cm (P < .0006, analysis of covariance). Height SDS was: AI, -1.73 (0.12); GH, -1.43 (0.14); AI/GH, -1.25 (0.12) (P < .0012). Those treated through 36 months grew more. Regardless of treatment duration, height SDS at near-final height n = 71; age, 17.4 (0.2) years; bone age, 15.3 (0.1) years; height achieved, ∼97.6% was: AI, -1.4 (0.1); GH, -1.4 (0.2); AI/GH, -1.0 (0.1) (P = .06). Absolute height change was: AI, +18.2 (1.6) cm; GH, +20.6 (1.5) cm; AI/GH, +22.5 (1.4) cm (P = .01) (expected height gain at -2.0 height SDS, +13.0 cm). AI/GH had higher fat free mass accrual. Measures of bone health, safety labs, and adverse events were similar in all groups. Letrozole caused higher T and lower estradiol than anastrozole. CONCLUSIONS: Combination therapy with AI/GH increases height potential in pubertal boys with ISS more than GH and AI alone treated for 24-36 months with a strong safety profile.