Growth Hormone Response to Thyrotropin-Releasing Hormone and Oral Glucose-Loading Tests in Tall Children and Adolescents

Abstract

The effects of TRH and oral glucose loading on the release of GH were investigated in 10 children or adolescents with constitutional tall stature. Eight of these children had a family history of above average height. The mean (and SEM) baseline GH levels (3.12 +/- 2.0 ng/ml) were similar to those in control subjects. Somatomedin activity, measured by sulfate incorporation into chick embryo cartilage, was elevated. Oral glucose loading caused an early significant increase in plasma GH at 30 min in 2 of these subjects and a late rise at 180 min in 4 others. Intravenous injection of synthetic TRH (0.2 mg/m2) caused a marked increase in plasma GH (17 +/- 3.0 ng/ml) in 7 of the 10 patients; the peak of GH was observed within the first hour after the injection of TRH in 3 cases, while a later peak was observed in the second hour after injection in 4 others. Peak plasma PRL (47 +/- 3.8 ng/ml) and TSH (20 +/- 1.2 microU/ml) levels in response to TRH were normal. These results suggest a disorder of hypothalamo-pituitary regulation of GH secretion in certain children with apparently constitutional tall stature. Similar findings in a probably preacromegalic girl are reported.