title: Changes in sleeping and basal energy expenditure and substrate oxidation induced by short term thyroxin administration in man.
abstract: The present study was designed to explore the thermogenic effect of thyroid hormone administration and the resulting changes in nitrogen homeostasis. Normal male volunteers (n = 7) received thyroxin during 6 weeks. The first 3-week period served to suppress endogenous thyroid secretion (180 micrograms T4/day). This dose was doubled for the next 3 weeks. Sleeping energy expenditure (respiratory chamber) and BMR (hood) were measured by indirect calorimetry, under standardized conditions. Sleeping heart rate was continuously recorded and urine was collected during this 12-hour period to assess nitrogen excretion. The changes in energy expenditure, heart rate and nitrogen balance were then related to the excess thyroxin administered. After 3 weeks of treatment, serum TSH level fell to 0.15 mU/L, indicating an almost complete inhibition of the pituitary-thyroid axis. During this phase of treatment there was an increase in sleeping EE and sleeping heart rate, which increased further by doubling the T4 dose (delta EE: +8.5 +/- 2.3%, delta heart rate +16.1 +/- 2.2%). The T4 dose, which is currently used as a substitutive dose, lead to a borderline hyperthyroid state, with an increase in EE and heart rate. Exogenous T4 administration provoked a significant increase in urinary nitrogen excretion averaging 40%. It is concluded that T4 provokes an important stimulation of EE, which is mostly mediated by an excess protein oxidation.
authors: Institute of Physiology, Faculty of Medicine, University of Lausanne, Switzerland.
authors: D
authors: D
authors: Bracco
authors: O
authors: O
authors: Morin
authors: H
authors: H
authors: Liang
authors: E
authors: E
authors: Jéquier
authors: A G
authors: AG
authors: Burger
authors: Y
authors: Y
authors: Schutz
mesh_terms: D000328:Adult; D001823:Body Composition / Q000502:physiology; D002153:Calorimetry, Indirect; D050260:Carbohydrate Metabolism; D004305:Dose-Response Relationship, Drug; D004734:Energy Metabolism / Q000187:drug effects* / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006706:Homeostasis / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000502:physiology; D050356:Lipid Metabolism; D008297:Male; D009584:Nitrogen / Q000378:metabolism / Q000652:urine; D010084:Oxidation-Reduction; D012890:Sleep / Q000187:drug effects* / Q000502:physiology; D013961:Thyroid Gland / Q000187:drug effects / Q000502:physiology; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D013997:Time Factors; D014284:Triiodothyronine / Q000097:blood
chemical_list: D014284:Triiodothyronine; D013972:Thyrotropin; D009584:Nitrogen; D013974:Thyroxine