L-proline loading for the assessment of pituitary GH reserve.

Intravenous insulin (0.1 U/kg body weight) and oral 1-proline (100 mg/kg body weight) tolerance tests were performed in 22 healthy and 30 short-statured children and adolescents and blood glucose, serum immunoreactive growth hormone (GH), immunoreactive insulin (IRI) and 1-proline were determined. The peak level of serum GH was significantly higher following insulin than after 1-proline. The proline loading correctly identified the normality of GH axis in 12 out of 22 controls and in 3 out of 7 normopituitary short-statured patients. The serum 1-proline levels consideration did not improve much the ability of 1-proline load to detect either the normal GH responsiveness or the pituitary insufficiency. The mechanism of GH stimulatory properties of 1-proline in some healthy subjects is not known.