title: Decreased lipid intermediate levels and lipid oxidation rates despite normal lipolysis in patients with hypothyroidism.
abstract: BACKGROUND
  Hypothyroidism decreases energy expenditure and combustion of fuels, but the reported effects on lipid metabolism and insulin sensitivity are divergent and there is a lack of studies assessing rates of lipolysis and lipid oxidation. The present study was conducted to test the hypotheses that hypothyroidism decreases lipolysis, blood concentrations of free fatty acid, lipid oxidation, and insulin sensitivity.
  
  
  METHODS
  We studied 11 hypothyroid patients (thyroid-stimulating hormone: 150 mU/L) with autoimmune thyroiditis (i) before and (ii) after 2 months of triiodothyronine-euthyroidism upon levothyroxine treatment and (iii) compared the patients to 10 healthy volunteers. Subjects underwent a 3-hour study in the basal state followed by a 3-hour euglycemic clamp study, and we used a combination of lipid blood concentrations, palmitate tracer dilution, and indirect calorimetry to assess lipid metabolism.
  
  
  RESULTS
  Compared to euthyroid control subjects and/or euthyroid posttreatment values hypothyroid patients were characterized by (i) 40%-50% decreased concentrations of plasma free fatty acids, palmitate, and 3-OH-butyrate (p < 0.05); (ii) >50% decreased lipid oxidation by indirect calorimetry (p < 0.001); (iii) unchanged whole-body lipolysis by palmitate dilution (all p's > 0.45); (iv) 50% increased triglyceride levels (p < 0.05); and (v) approximately 30% decreased insulin sensitivity judged by glucose infusion rate values (p = 0.05).
  
  
  CONCLUSIONS
  Our data show that hypothyroidism leads to decreased concentrations and oxidation rates of lipid intermediates and increased triglyceride concentrations in the presence of unaltered rates of lipolysis. The combination of normal lipolysis, low lipid oxidation rates, and high triglyceride concentrations is compatible with increased triglyceride synthesis.
authors.affiliation: Medical Department M (Endocrinology and Diabetes), Aarhus University Hospital , Aarhus, Denmark. signegjedde@dadlnet.dk
authors.forename: Signe
authors.initials: S
authors.lastname: Gjedde
authors.forename: Lars Christian
authors.initials: LC
authors.lastname: Gormsen
authors.forename: Jørgen
authors.initials: J
authors.lastname: Rungby
authors.forename: Søren
authors.initials: S
authors.lastname: Nielsen
authors.forename: Jens Otto Lunde
authors.initials: JO
authors.lastname: Jørgensen
authors.forename: Steen Bønløkke
authors.initials: SB
authors.lastname: Pedersen
authors.forename: Anne Lene
authors.initials: AL
authors.lastname: Riis
authors.forename: Jørgen
authors.initials: J
authors.lastname: Weeke
authors.forename: Niels
authors.initials: N
authors.lastname: Møller
mesh_terms: D000328:Adult; D002153:Calorimetry, Indirect / Q000379:methods; D016022:Case-Control Studies; D005230:Fatty Acids, Nonesterified / Q000737:chemistry; D005260:Female; D015309:Glucose Clamp Technique; D006801:Humans; D007037:Hypothyroidism / Q000097:blood / Q000276:immunology*; D007328:Insulin / Q000378:metabolism; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry*; D008066:Lipolysis; D008297:Male; D008875:Middle Aged; D010169:Palmitic Acids / Q000737:chemistry; D013967:Thyroiditis, Autoimmune / Q000473:pathology; D013974:Thyroxine / Q000494:pharmacology
chemical_list: D005230:Fatty Acids, Nonesterified; D007328:Insulin; D008055:Lipids; D010169:Palmitic Acids; D013974:Thyroxine