Effect of long-term growth hormone therapy on bone age and pubertal maturation in boys with and without classic growth hormone deficiency

We evaluated the effect of growth hormone (GH) therapy on bone age, pubertal maturation and predicted adult height in two groups of boys treated for 4 years: 40 growth hormone-deficient boys who had growth hormone response to provocative stimulation <10 μg/L (GHD group) and 43 boys whose stimulated growth hormone ≥10 μg/L (group with neurosecretory dysfunction (NSD). All patients had a subnormal integrated concentration of growth hormone ≤3.2 μg/L, height <-2 SD, growth velocity <4.5 cm/yr, and bone age ≤-2 SD for chronologic age. Patients were treated with recombinant growth hormone, 0.1 mg/kg per dose given three times a week. The pretreatment height SD of the GHD group (-3.6±1.0) was less than that of the NSD group (-2.7±0.7; p<0.001). After 4 years of therapy, both groups had catch-up growth (GHD group to -2.0±1.3 height SD (n=35), and NSD group to -1.4±0.7 height SD (n=32)); the rate of height SD gain was better in patients with GHD (p<0.01). The response to growth hormone was inversely related to pretreatment chronologic age (p<0.001). The Tanner-Whitehouse II predicted adult height improved for both groups: +9.3±7.7 cm in the GHD group, giving an adult height SD of -0.9±1.0, and +5.4±5.5 cm in patients with NSD, for an adult height SD if -0.8±0.7. Testosterone levels became higher in the NSD group after 2 years and remained higher at year 4. We conclude that patients respond favorably to growth hormone therapy and in a manner similar to patients with GHD. Initiation of therapy at a younger age gives a greater improvement in gained height and predicted adult height.