The growth hormone (GH)-dependent growth factors insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 (IGFBP-3) may be superior to provocative GH testing in diagnosing GH deficiency (GHD) in children. In adults with brain tumors (BT) and GHD, however, provocative GH testing more accurately reflects GHD than either IGF-I or IGFBP-3. We assessed growth factor levels in pediatric BT patients with respect to pubertal stage, growth velocity, and body mass index.
Pre-GH treatment growth factor levels were available for 72 children (52m, 21f) diagnosed with GHD by: history of pituitary resection or ablative doses of pituitary irradiation, growth deceleration, and subnormal responses to standard provocative growth hormone tests. IGF-I levels were low (<5%) in 60 of 70 children with GHD (85.7%), and IGFBP-3 levels were low in 22 of 42(52.4%). GHD children with normal growth factors had a higher mean Tanner stage, 2.00 ± 1.00 vs. 1.40 ± 0.79 for IGF-I and 1.75 ± 1.07 vs. 1.18 ± 0.50 for IGFBP-3 (p < 0.05). Low IGF-1 levels were found in 14/15 children with craniopharyngioma (CR) (93.3%) and 27/30 with medulloblastoma (ME) (90.0%) but only in 7/12 children with hypothalamic/chiasmatic glioma (HG) (58.3%) (p < 0.05). IGFBP-3 levels were low in 9/13 CR patients (69.2%), 8/15 ME patients (53.3%), and 2/8 HG patients(25.0%) (p = ns). Pubertal development varied significantly among tumor types, with mean Tanner stages of 1.25 ± 0.58 for CR, 1.42 ± 0.76 for ME, and 2.33 ± 1.15 for HG (p < 0.01). Pre-GH treatment growth velocity Z-scores were significantly lower in patients with low vs. normal IGF-I levels (-3.10 ± 1.95 vs. -0.94 ± 2.43, p < 0.005), but not in patients with low vs. normal IGFBP-3 levels (-2.94 ± 2.03 vs.-2.07 ± 2.76, p = ns). Body mass index differed significantly among tumor types but not between patients with low vs. normal growth factor levels.
