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Ghrelin drives GH secretion during fasting in man
Alex F Muller1, Steven W J Lamberts, Joop A M J L Janssen
1Division of Endocrinology, Department of Internal Medicine, Erasmus University Medical Centre, Rotterdam, The Netherlands. amuller@diakhuis.nl
European Journal of Endocrinology
|February 9, 2002
Summary
Fasting significantly increases growth hormone (GH) secretion in humans. This study reveals that elevated ghrelin levels, not hypothalamic factors, are the primary driver of this GH release during fasting.
Area of Science:
- Endocrinology
- Metabolism
Background:
- Fasting is known to increase serum growth hormone (GH) concentrations.
- Traditionally, hypothalamic GH-releasing hormone and somatostatin were considered the primary regulators.
- Ghrelin, a stomach-derived hormone, also stimulates GH release and is elevated during fasting.
Purpose of the Study:
- To investigate the role of ghrelin in fasting-induced GH secretion.
- To determine if elevated ghrelin levels are the main mechanism for increased GH during fasting.
Main Methods:
- A double-blind, placebo-controlled crossover study was conducted in ten healthy males.
- Fasting conditions with and without GH receptor blockade (pegvisomant) were compared.
- Serum levels of GH, ghrelin, insulin, glucose, and free fatty acids were measured.
Main Results:
- Fasting induced a diurnal rhythm in ghrelin concentrations, which correlated with GH levels.
- This ghrelin rhythm was independent of changes in insulin, glucose, or free fatty acids.
- GH receptor blockade did not alter the fasting-induced ghrelin rhythm.
Conclusions:
- Ghrelin is identified as the principal factor responsible for enhanced GH secretion during fasting.
- This finding shifts the understanding of GH regulation during caloric restriction.