Glucoregulatory function of thyroid hormones: role of pancreatic hormones.
Glucose metabolism was investigated in humans before and 14 days after 300 micrograms L-thyroxine (T4)/day using a sequential clamp protocol during short-term somatostatin infusion (500 micrograms/h, 0-6 h) at euglycemia (0-2.5 h), at 165 mg/dl (2.5-6 h), and during insulin infusion (1.0 mU.kg-1.min-1, 4.5-6 h). T4 treatment increased plasma T4 (+96%) and 3,5,3'-triiodothyronine (T3, +50%), energy expenditure (+8%), glucose turnover (+32%), and glucose oxidation (Glucox +87%) but decreased thyroid-stimulating hormone (-96%) and nonoxidative glucose metabolism (Glucnonox, -30%) at unchanged lipid oxidation (Lipox). During somatostatin and euglycemia glucose production (Ra, -67%) and disposal (Rd, -28%) both decreased in euthyroid subjects but remained at -22% and -5%, respectively, after T4 treatment. Glucox (control, -20%; +T4, -25%) fell and Lipox increased (control, +42%; +T4, +45%) in both groups, whereas Glucnonox decreased before (-36%) but increased after T4 (+57%). During somatostatin infusion and hyperglycemia Rd (control, +144%; +T4, +84%) and Glucnonox (control, +326%; +T4, +233%) increased, whereas Glucox and Lipox remained unchanged. Insulin further increased Rd (+76%), Glucox (+155%), and Glucnonox (+50%) but decreased Ra (-43%) and Lipox (-43%). All these effects were enhanced by T4 (Rd, +38%; Glucox, +45%; Glucnonox, +35%; Ra, +40%; Lipox, +11%). Our data provide evidence that, in humans, T3 stimulates Ra and Rd, which is in part independent of pancreatic hormones.
Müller
M J
MJ
Medizinische Hochschule Hannover, University of Hannover, Federal Republic of Germany.
Burger
A G
AG
Ferrannini
E
E
Jequier
E
E
Acheson
K J
KJ
D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D002096:C-Peptide / Q000097:blood; D004734:Energy Metabolism / Q000187:drug effects; D005947:Glucose / Q000378:metabolism*; D006019:Glycolysis; D006706:Homeostasis; D006801:Humans; D007328:Insulin / Q000097:blood; D050356:Lipid Metabolism; D008657:Metabolic Clearance Rate / Q000187:drug effects; D010084:Oxidation-Reduction; D010187:Pancreatic Hormones / Q000502:physiology*; D013004:Somatostatin; D013963:Thyroid Hormones / Q000502:physiology*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood / Q000494:pharmacology; D014284:Triiodothyronine / Q000097:blood; D014316:Tritium
D001786:Blood Glucose; D002096:C-Peptide; D007328:Insulin; D010187:Pancreatic Hormones; D013963:Thyroid Hormones; D014284:Triiodothyronine; D014316:Tritium; D013004:Somatostatin; D013972:Thyrotropin; D005947:Glucose; D013974:Thyroxine