Serum Growth-Hormone-Binding Protein and Growth during Treatment of Children with Hyperthyroidism and Hypotyroidism

Thyroid hormone greatly influences postnatal growth in children and secretion of growth hormone (GH). To study the relation between serum GH-binding protein (GHBP), which is expressed as tissue GH-receptor concentrations and influenced by the nutritional state, thyroid hormone and growth development, we measured serum GHBP in six children with hyperthyoidism and six children with hypothyroidism using samples taken before and during treatment. Mean treatment periods of these diseases are 13 and 10 months, respectively. Mean height velocity standard deviation (SD) score decreased from 2.51 to -0.62, but was not significantly related to the treatment, in hyperthyroidism, and significantly increased from -3.02 to 5.27 due to the treatment in hypothyroidism. There was no significant difference of GHBP levels before the treatment between hyper- and hypothyroidism (mean 9.59 vs. 8.53ng/mL). In hyperthyroidism, GHBP levels decreased significantly during the treatment. In hypothyroidism, insulin-like growth factor I (IGF-I) and IGF binding protein-3 (IGFBP-3) increased, but percent overweight decreased significantly, and GHBP levels did not significantly change during the treatment.ΔGHBP was defined as the change in GHBP during treatment to examine whether or not the change in GHBP was parallel to the change in thyroid hormone. ΔGHBP showed no correlation with Δ height velocity SD score. ΔGHBP showed a significant positive correlation with ΔT4 level and negative correlation with Δpercent overweight. However, only ΔT4 was identified as an influencing factor on ΔGHBP by stepwise multiple regression analysis.The data demonstrate that the changes in serum GHBP level were influenced by the changes in T4 levels during the treatment of abnormal thyroid function. The data also show that GHBP was unrelated to height gain associated with treatment in hyperthyroidism and hypothroidism.