Session: FP20-Growth: Clinical Trials & Observational Studies
Room 122 (Moscone Center)
Poster Board SUN-626
Design: Inclusion criteria were male >10 years, bone age ≤ 14 years, height < 5th%ile and/or PAH >10 cm below mid-parental height, Tanner ≥ G2 (testicular volume ≥ 4cc), LH >0.3 IU/L, and testosterone >15 ng/dL. Subjects were randomized to standard oral daily doses of A (1 mg) or L (2.5 mg), with no untreated group. Baseline and follow-up visits included physical exam and hormone assessment every 6 months, annual bone age, and DXA and lateral spine film every 2 years.
Results: 45 patients have been randomized to date; 33 boys have completed 6 months of therapy, and 25 have completed 12 months. No boys were concurrently on growth hormone. At enrollment, average age was 14.2 ±1.3 y (range 10.2-16.0) with combined baseline lab values as follows (mean ±SD, performed at Esoterix): LH 2.1 ±1.2 IU/L, testosterone 202 ±152 ng/dL, estradiol 6.2 ±5.4 pg/mL, IGF-I 315 ±123 ng/mL, and IGFBP-3 3.2 ±0.7 mg/L, with no between-group differences in any parameters. At 6 months, significant differences were seen between the A and L groups, respectively: LH 2.8 ±1.2 vs. 6.8 ±3.9, testosterone 496 ±228 vs. 1067 ±397, estradiol 3.5 ±2.2 vs. 1.8 ±0.7, IGF-I 356 ±93 vs. 252 ±71, and IGFBP-3 3.4 ±0.7 vs. 2.8 ±0.7 (all p <0.02). Mean levels were unchanged between the 6 and 12 month visits, and the between-group differences persisted at 12 months. There were no adverse events in the first year.
Conclusion: Compared with anastrozole, letrozole results in higher serum levels of LH and testosterone, and lower levels of estradiol, IGF-I, and IGF-BP3, in the first year of therapy. Despite pubertal advance and a robust increase in testosterone in both treatment groups, especially with letrozole, IGFs failed to rise, possibly related to the intended suppression of estrogen levels. Aromatase inhibitors result in dramatic short-term hormonal alterations and should be utilized with caution until additional studies have reached final height.
Nothing to Disclose: RBK, SLP, DIS, EKN
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