26 excesive growth hormone secretion of prepubertal onset

A 10.9 years old girl was studied for tall stature, with onset before the age of 6. Her height of 175.6 cm was ± 4.4 SD above the mean. The basal level of growth hormone (GH) was elevated on several occasions (9.9-20 ng/ml). The phenotype was otherwise normal and the bone age was advanced. (12.5 years for 10,9 years of chronological age. The oral glucose loading was ineffective in suppressing GH levels and stimulation tests with clonidine and TRH did nor modify substantially the basal GH levels. Computered Tomography and Magnetic Resonance Imaging, failed to show a pituitary mass. The plasma IGF-I level was 4.27 U/ml, within the normal pubertal range. The extraction IGF-I level was elevated (> 2 SD P 50), and the IGF-Binding Protein 3 was 5-10 times the normal control levels, suggesting GH hypersecretion. A terapeutic trial with Bromocryptine was started at age 11.91 years when she was 180.3 cm tall, resulting in a marked slowing of her growth rate. IGF.I levels decreased gradually, without any change in the basal GH levels. After 10 months of treatment she grew only 1.2 cm, less than the expected rate in her first post-menarchal year. We wish to emphasize the usefullness of IGF-I and IGF-BPs measurements in the diagnosis and follow-up of GH hypersecretion.