Effects of high-dose growth hormone on glucose and glycerol metabolism at rest and during exercise in endurance-trained athletes.
BACKGROUND
Recombinant human-GH (r-hGH), in supraphysiological doses, is self-administered by athletes in the belief that it is performance enhancing.


OBJECTIVE
The objective of this study was to determine whether r-hGH alters whole-body glucose and glycerol metabolism in endurance-trained athletes at rest and during and after exercise.


METHODS
This was a 4-wk double-blind placebo-controlled trial.


METHODS
This study was conducted at St. Thomas Hospital (London, UK).


METHODS
Twelve endurance-trained male athletes were recruited and randomized to r-hGH (0.2 U/kg.d) (n = 6) or identical placebo (n = 6) for 4 wk. One (placebo group) withdrew after randomization.


METHODS
Intervention was conducted by randomization to r-hGH (0.2 U/kg x d) or identical placebo for 4 wk.


METHODS
Whole-body rates of appearance (Ra) of glucose and glycerol (an index of lipolysis) and rate of disappearance of glucose were measured using infusions of d-[6-6-2H2]glucose and 2H5-glycerol.


RESULTS
Plasma levels of glycerol and free fatty acids and glycerol Ra at rest and during and after exercise increased during r-hGH treatment (P < 0.05 vs. placebo). Glucose Ra and glucose rate of disappearance were greater after exercise during r-hGH treatment (P < 0.05 vs. placebo). Resting energy expenditure and fat oxidation were greater under resting conditions during r-hGH treatment (P < 0.05 vs. placebo).


CONCLUSIONS
r-hGH in endurance-trained athletes increased lipolysis and fatty acid availability at rest and during and after exercise. r-hGH increased glucose production and uptake rates after exercise. The relevance of these effects for athletic performance is not known.
Healy
M L
ML
Department of Diabetes and Endocrinology, Guy's, King's and St. Thomas' School of Medicine, St. Thomas Hospital, London SE1 7EH, United Kingdom.
Gibney
J
J
Pentecost
C
C
Croos
P
P
Russell-Jones
D L
DL
Sönksen
P H
PH
Umpleby
A M
AM
D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D002153:Calorimetry, Indirect; D018592:Cross-Over Studies; D004040:Dietary Carbohydrates / Q000378:metabolism; D004311:Double-Blind Method; D004734:Energy Metabolism / Q000187:drug effects; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005227:Fatty Acids / Q000378:metabolism; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005990:Glycerol / Q000378:metabolism*; D013006:Growth Hormone / Q000494:pharmacology*; D019382:Human Growth Hormone / Q000097:blood; D006801:Humans; D008066:Lipolysis / Q000187:drug effects; D008297:Male; D010084:Oxidation-Reduction; D010807:Physical Endurance / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology*; D012146:Rest / Q000502:physiology*
D001786:Blood Glucose; D004040:Dietary Carbohydrates; D005227:Fatty Acids; D005230:Fatty Acids, Nonesterified; D019382:Human Growth Hormone; D013006:Growth Hormone; D005990:Glycerol