Similar clinical features among patients with severe adult growth hormone deficiency diagnosed with insulin tolerance test or arginine or glucagon stimulation tests

OBJECTIVE: To determine whether insulin tolerance tests (ITTs), arginine stimulation tests (ASTs), and glucagon stimulation tests (GST) identify patients who have similar clinical features of growth hormone (GH) deficiency when a diagnostic GH threshold of 3 μg/L is used. METHODS: Data were obtained from the KIMS database (Pfizer International Metabolic Database). Comparisons were made between patients who underwent ITT, AST, or GST for GH peak, body mass index, lipids, waist circumference, waist-to-hip ratio, and quality of life. RESULTS: A total of 5453 tests were available from 4867 patients registered in the database (ITT = 3111, AST = 1390, GST = 952). Significant (P<.001) intraindividual correlations were observed between the GH peaks for ITT vs AST (r = 0.655), ITT vs GST (r = 0.445), and AST vs GST (r = 0.632). GH peaks in response to all tests were negatively correlated to the number of additional pituitary hormone deficiencies and positively correlated to the insulinlike growth factor 1 standard deviation score. Body mass index had a negative influence on all 3 tests. Most clinical variables did not differ between the groups when comparing GH-deficient patients according to the diagnostic test used. The only exceptions that showed any difference were body mass index (slightly higher in the AST and GST groups), triglyceride levels (increased in the GST group), and insulinlike growth factor 1 (standard deviation score) (lower in the ITT and AST groups than in the GST group). Waist circumference was greater and quality of life was worse in the GST group than in the other groups. CONCLUSIONS: The ITT, AST, and GST produce similar GH peaks, are influenced by similar clinical factors, and identify patients with similar features of GH deficiency at a diagnostic threshold of 3 μg/L

Clinical implications of residual growth hormone (GH) response to provocative testing in adults with severe GH deficiency

Context: The diagnosis of GH deficiency ( GHD) in adults is based on provocative tests of GH release, all influenced by clinical factors. It is unknown whether the amount of residual GH reserve under the cutoff value has any physiological implication. Objectives: We used a large pharmacoepidemiological database of adult GHD (KIMS) and tested the impact of confounding factors on GH release of no greater than 3 mu g/liter after an insulin tolerance test ( ITT) and evaluated its potential physiological role. Design, Settings, and Patients: A total of 1098 patients fulfilled the criteria of having a GH peak of no greater than 3 mu g/liter during ITT as well as documented IGF-I levels. Outcomes: The impact of underlying hypothalamic-pituitary disease, age, gender, body weight, as well as treatment modalities such as irradiation on peak GH level to ITT was evaluated, and the correlations between GH peak and targets of GH action were analyzed. Results: The GH response to ITT was regulated by gender, age, and the number of additional pituitary deficiencies. In a multivariate evaluation, the extent of hypothalamic-pituitary dysfunction was the most important single predictor of GH peak in ITT. GH peaks in ITT were positively related to IGF-I levels and high-density lipoprotein-cholesterol, as well as inversely to triglycerides. Conclusions: Even in adult severe GHD, GH release appears to be regulated by factors defined to play an important role in normal GH secretion. The impact of very low GH release on IGF-I and lipid parameters indicates a persistent physiological role of low GH concentrations in severely affected patients with GHD