LOW GROWTH HORMONE-BINDING PROTEIN IN INFANTS WITH CONGENITAL HYPOTHYROIDISM

We evaluated the circulating levels of GH, insulin-like growth factor I (IGF-I), GH-binding protein (GHBP), and IGF-binding protein-3 (IGFBP -3) before L-T-4 therapy in 19 infants with congenital hypothyroidism (CH), aged 12-29 days, diagnosed by neonatal screening and in a group of age- and sex-matched control infants. The same parameters were reev aluated after several months of treatment. Serum GHBP was measured by the high performance liquid chromatography-gel filtration method; seru m GH, IGF-I, and IGFBP-3 levels were determined by commercial kits. Th e hypothyroid patients, before beginning therapy, presented significan tly lower GHBP values than controls (P < 0.0001); during treatment, th ese values increased significantly; however, after 6 months they were still significantly lower than control values (P < 0.01). The pretreat ment levels of GH were not significantly different from control values ; after 1 month of treatment, GH did not show the decrease observed in controls and, therefore, was significantly higher (P < 0.01). The pre treatment levels of IGF-I were not significantly different from contro l values, but were lower in patients with severe than in those with mi ld hypothyroidism. They decreased at about 4 months of life and became significantly lower than control values at about 7 months of age (P < 0.05). In conclusion, it may be hypothesized that the condition of CH induces a change in GHBP expression, perhaps beginning in fetal life. The intrauterine production of IGF-I seems to be independent of the l evels of GHBP and partially affected by fetal thyroid function.