Insulin-like growth factors (IGF) I and II and IGF binding proteins 1, 2 and 3 during low-dose growth hormone (GH) infusion and sequential euglycemic and hypoglycemic glucose clamps: studies in GH-deficient patients.
Level 3 - non-randomized controlled study
Non-randomized controlled crossover physiological trial in humans
PubMed 7687807 · doi:10.1530/acta.0.1280513
What was done
Six growth hormone (GH)-deficient adolescents were studied overnight and during the following day under two conditions (GH infusion at 35 µg/h vs saline) after a 24-hour withdrawal of usual GH therapy. Daytime assessments included a postabsorptive basal state followed by sequential euglycemic (5 mmol/l) and hypoglycemic (3 mmol/l) glucose clamps to measure short-term changes in IGF-I, IGF-II, and IGFBP-1, 2, and 3.
What was found
No numerical values or effect sizes were reported in the abstract. Directional findings include: - Nocturnal IGF-I, IGF-II, IGFBP-2, and IGFBP-3 levels remained stable in both GH and saline conditions. - Nocturnal IGFBP-1 increased and correlated inversely with insulin in both conditions. - Mean nocturnal IGFBP-2 and IGFBP-3 levels had a significant inverse correlation. - Daytime IGF-I declined slowly during saline infusion, while IGF-II remained stable across both studies. - Daytime IGFBP-1 declined significantly during the basal state and clamp periods unaffected by GH levels, while IGFBP-2 remained stable, and IGFBP-3 declined insignificantly during saline infusion.
Why it matters
This study clarifies that IGFBP-1 is acutely responsive to changes in insulin and glycemic status rather than short-term GH levels, whereas IGF-II, IGFBP-2, and IGFBP-3 are largely unresponsive to acute glycemic and short-term GH variations.
Limits
The study is limited by a very small sample size (6 participants) and a specific GH-deficient adolescent population following brief GH withdrawal. The abstract reports no numerical concentration data or exact p-values and is truncated.
Cited by
- contradicts As insulin levels decrease, levels of IGF-binding protein 3 (IGFBP-3) increase.