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Thyroid hormone action on lipid metabolism in humans: A role for endogenous insulin

Authors
Journal
Metabolism
0026-0495
Publisher
Elsevier
Publication Date
Volume
39
Issue
5
Identifiers
DOI: 10.1016/0026-0495(90)90006-x

Abstract

Abstract The effects of moderate hyperthyroidism on lipid metabolism were investigated in six healthy subjects before and after thyroxine treatment (300 μg/d). T 4-treatment increased basal metabolic rate (+8%) and glucose oxidation (+87%), without affecting lipid oxidation, plasma free fatty acids, glycerol, and β-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 β-hydroxybutyrate (+343%), but decreased glucose oxidation (−20%). Similar effects were observed after T 4-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.

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