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Summary
Diabetics show elevated growth hormone (GH) levels due to increased secretion, not reduced breakdown. Total distribution volume (TDV) for GH decreases with longer diabetes duration, indicating disease progression impacts GH kinetics.
Area of Science:
- Endocrinology
- Metabolic Disorders
- Pharmacokinetics
Background:
- Elevated plasma growth hormone (GH) concentrations are observed in insulin-treated and juvenile diabetics.
- This elevation has been attributed to either increased pituitary GH secretion or reduced GH catabolism.
Purpose of the Study:
- To investigate the kinetics of GH in diabetic patients.
- To determine whether elevated GH levels are due to increased secretion or decreased metabolism.
Main Methods:
- Studied GH kinetics in 24 diabetic patients and 14 normal subjects using 125-I-GH tracer.
- Calculated metabolic clearance rate (MCR), fractional catabolic rate (FCR), initial distribution volume (IDV), and total distribution volume (TDV).
- Estimated irreversible hormone loss (IHL240) using MCR and endogenous GH plasma concentrations.
Main Results:
- Diabetic patients exhibited normal MCR values compared to controls.
- Higher plasma GH concentrations in diabetics, with normal MCR, resulted in significantly increased IHL240, indicating enhanced GH secretion.
- Total distribution volume (TDV) decreased in long-term diabetics (over 10 years) but remained normal in short-term diabetics.
Conclusions:
- Increased GH secretion, not reduced catabolism, is responsible for elevated plasma GH in diabetics.
- Progressive decrease in TDV correlates with diabetes duration, suggesting disease progression impacts GH distribution.