Thyroid hormone action on lipid metabolism in humans: a role for endogenous insulin.
The effects of moderate hyperthyroidism on lipid metabolism were investigated in six healthy subjects before and after thyroxine treatment (300 micrograms/d). T4-treatment increased basal metabolic rate (+8%) and glucose oxidation (+87%), without affecting lipid oxidation, plasma free fatty acids, glycerol, and beta-hydroxybutyrate. During euthyroidism, a hypoinsulinaemic-euglycaemic 150-minute clamp protocol increased energy expenditure (+3%), lipid oxidation (+42%), plasma free fatty acids (+254%), glycerol (+232%), and beta-hydroxybutyrate (+343%), but decreased glucose oxidation (-20%). Similar effects were observed after T4-treatment, but hyperthyroidism induced disproportionate increases in energy expenditure (+7%), plasma glycerol (+310%), and ketone body levels (+436%). We conclude that moderate hyperthyroidism enhances hypoinsulinemia-induced increases in lipolysis, free fatty acid recycling, and ketogenesis without affecting lipid oxidation. Thus basal insulin may camouflage some of thyroid hormone action on lipid metabolism.
Müller
M J
MJ
Medizinische Hochschule Hannover, Universität Hannover, FRG.
Acheson
K J
KJ
Jequier
E
E
Burger
A G
AG
D020155:3-Hydroxybutyric Acid; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D002096:C-Peptide / Q000097:blood; D005227:Fatty Acids / Q000097:blood; D005934:Glucagon / Q000097:blood; D005990:Glycerol / Q000097:blood; D006801:Humans; D006885:Hydroxybutyrates / Q000097:blood; D006980:Hyperthyroidism / Q000378:metabolism; D007328:Insulin / Q000097:blood / Q000502:physiology; D050356:Lipid Metabolism; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000187:drug effects; D010187:Pancreatic Hormones / Q000097:blood; D013004:Somatostatin / Q000494:pharmacology; D013963:Thyroid Hormones / Q000502:physiology*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood / Q000494:pharmacology; D014284:Triiodothyronine / Q000097:blood
D001786:Blood Glucose; D002096:C-Peptide; D005227:Fatty Acids; D006885:Hydroxybutyrates; D007328:Insulin; D010187:Pancreatic Hormones; D013963:Thyroid Hormones; D014284:Triiodothyronine; D013004:Somatostatin; D013972:Thyrotropin; D005934:Glucagon; D005990:Glycerol; D013974:Thyroxine; D020155:3-Hydroxybutyric Acid