Related Experiment Videos
L-proline loading for the assessment of pituitary GH reserve
Insights
Oral 1-proline and intravenous insulin tolerance tests assessed growth hormone (GH) axis function in children. Insulin induced a higher peak GH response than 1-proline, with limited diagnostic utility for proline in short stature.
Area of Science:
- Pediatric Endocrinology
- Growth Hormone Physiology
- Metabolic Testing
Background:
- Assessing the growth hormone (GH) axis is crucial for diagnosing short stature in children.
- Standard diagnostic tests for GH deficiency or responsiveness can be invasive or have limitations.
Purpose of the Study:
- To compare the efficacy of oral 1-proline loading versus intravenous insulin tolerance testing in evaluating GH axis function.
- To determine if serum 1-proline levels enhance the diagnostic accuracy of the 1-proline load test.
Main Methods:
- Intravenous insulin tolerance test (0.1 U/kg) and oral 1-proline tolerance test (100 mg/kg) were administered to healthy children and those with short stature.
- Blood glucose, serum immunoreactive growth hormone (GH), immunoreactive insulin (IRI), and serum 1-proline were measured.
Main Results:
- Peak serum GH levels were significantly higher after insulin administration compared to 1-proline.
- The 1-proline load test correctly identified normal GH axis function in 12/22 controls and 3/7 short-statured patients.
- Incorporating serum 1-proline levels did not substantially improve the test's ability to detect normal GH responsiveness or pituitary insufficiency.
Conclusions:
- Intravenous insulin tolerance test appears to elicit a stronger GH response than oral 1-proline in pediatric subjects.
- Oral 1-proline loading has limited diagnostic value for assessing GH axis normality or pituitary insufficiency in short-statured children.
- The mechanism underlying GH stimulation by 1-proline in some individuals remains unclear.
Abstract:
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.