Growth hormone therapy and growth in children with Noonan's syndrome: results of 3 years' follow-up.

Growth data from the first 3 yr of a multicenter study examining the efficacy and safety of recombinant human GH [rhGH; 4 IU (1.3 mg)/m(2).day, sc] in children with Noonan's syndrome (NS) are reported for 23 subjects. Sixteen male and seven female patients (age, 9.3 +/- 2.6 yr at onset of GH therapy, mean +/- SD; range, 4.8-13.7) were each assessed at 1, 2, and 3 yr after starting treatment. Comparisons were made with a group of eight subjects (six males and two females, age, 9.0 +/- 4.1 yr; range, 4.1-14.8) with NS, not treated with rhGH, measured over the same period. All treated subjects underwent annual cardiac assessment. Height SD score increased from -2.7 +/- 0.4 at the start of GH therapy to -1.9 +/- 0.9 3 yr later (P < 0.001, two-tailed t test). This corresponded to an increase in height from 116.1 +/- 13.2 to 137.3 +/- 14.0 cm. Height velocity increased from 4.4 +/- 1.7 cm/yr in the year before treatment to 8.4 +/- 1.7 (P < 0.001), 6.2 +/- 1.7 (P < 0.001), and 5.8 +/- 1.8 (P = 0.01, two-tailed t test compared with baseline) during the first, second, and third years of GH treatment, respectively. Height acceleration was not significant during the second or third years when pubertal subjects were excluded. The comparison group showed an increase in height from 116.0 +/- 19.8 to 131.9 +/- 21.1 cm over the 3 yr (height SD score, -2.7 +/- 0.6 to -2.4 +/- 0.7, P = 0.3). None of the 23 children developed hypertrophic cardiomyopathy during GH treatment. The increase in growth rate in NS resulting from 1 yr of GH therapy seems to be maintained during the second year, although height velocity shows a less significant increase over pretherapy values. Possible abnormal anabolic effects of rhGH on myocardial thickness were not confirmed, and no treated patient developed features of hypertrophic cardiomyopathy.