Growth hormone deficiency and the measurement of somatomedin C/IGF-I: the influence of sexual maturation.

Fifty-nine short children 2-19 years, 25 females and 34 males, were studied for clinical and biochemical evidence of growth hormone deficiency (GHD). Group 1 (n = 32), mean height SDS -3.26 +/- 1.5, mean retardation of bone age 2 years, had a mean peak GH of 6.1 +/- 3.7 mIU/l during tests of GH release, and were classified as GHD. Group 2 (n = 27), had a mean height SDS of -2.65 +/- 1, mean bone age retardation of 1.7 years and had a mean peak GH during provocation tests of 24.3 +/- 11.1 mIU/l and were classified as non-GHD. Basal IGF-I concentrations were correlated with height and bone age, for both groups and for GHD children, with pubertal score. Neither peak GH values nor integrated GH concentrations in a provocative test were correlated with IGF-I values. The minimum IGF-I concentrations occurred at a bone age of 8 years, the reference point that was taken as the average expected time of maturational change. IGF-I concentrations rose in five GHD children when their bone age exceeded 8 years and when their free testosterone was greater than 10 pmol/l. Eighty-nine per cent of the GHD children with a bone age at or below 8 years were identified as GHD from their basal IGF-I values, but for all bone ages this fell to 62.5%. Basal IGF-I values appear to be less discriminatory for identification of GHD as sexual maturity and bone age advance.

Duke Scholars

Author John Wiley Williams Jr. Medicine, General Internal Medicine