title: Metabolic effects of liothyronine therapy in hypothyroidism: a randomized, double-blind, crossover trial of liothyronine versus levothyroxine.
abstract: BACKGROUND
  Levothyroxine (L-T(4)) therapy is based on the assumption that the conversion of T(4) into T(3) provides adequate amounts of active hormone at target tissues. However, in rodents, L-T(4) alone does not restore a euthyroid state in all tissues. Previous combination L-T(4)/liothyronine (L-T(3)) therapy trials focused on quality-of-life endpoints, and limited information is available on the effects on other measures of thyroid hormone action.
  
  
  OBJECTIVE
  Our objective was to evaluate the efficacy of thyroid hormone replacement with L-T(4) or L-T(3) at doses producing equivalent normalization of TSH.
  
  
  METHODS
  Fourteen hypothyroid patients participated in this randomized, double-blind, crossover intervention at the National Institutes of Health Clinical Center.
  
  
  METHODS
  L-T(3) or L-T(4) were administered thrice daily to achieve a target TSH from 0.5-1.5 mU/liter. Volunteers were studied as inpatients after 6 wk on a stable dose and at the target TSH.
  
  
  METHODS
  Serum thyroid hormones, lipid parameters, and indices of glucose metabolism were evaluated.
  
  
  RESULTS
  No difference was observed in TSH between L-T(3) and L-T(4) treatments. L-T(3) resulted in significant weight loss [L-T(4), 70.6 ± 12.5, vs. L-T(3), 68.5 ± 11.9 kg (P = 0.009)] and in a 10.9 ± 10.0% decrease in total cholesterol (P = 0.002), 13.3 ± 12.1% decrease in low-density lipoprotein-cholesterol (P = 0.002), and an 18.3 ± 28.6% decrease in apolipoprotein B (P = 0.018). No significant differences were observed in high-density lipoprotein-cholesterol, heart rate, blood pressure, exercise tolerance, or insulin sensitivity.
  
  
  CONCLUSIONS
  The substitution of L-T(3) for L-T(4) at equivalent doses (relative to the pituitary) reduced body weight and resulted in greater thyroid hormone action on the lipid metabolism, without detected differences in cardiovascular function or insulin sensitivity.
authors.affiliation: Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Building 10, CRC, Room 6-3940, 10 Center Drive, MSC 1613, Bethesda, Maryland 20892-1613, USA. fc93a@nih.gov
authors.forename: Francesco S
authors.initials: FS
authors.lastname: Celi
authors.forename: Marina
authors.initials: M
authors.lastname: Zemskova
authors.forename: Joyce D
authors.initials: JD
authors.lastname: Linderman
authors.forename: Sheila
authors.initials: S
authors.lastname: Smith
authors.forename: Bart
authors.initials: B
authors.lastname: Drinkard
authors.forename: Vandana
authors.initials: V
authors.lastname: Sachdev
authors.forename: Monica C
authors.initials: MC
authors.lastname: Skarulis
authors.forename: Merel
authors.initials: M
authors.lastname: Kozlosky
authors.forename: Gyorgy
authors.initials: G
authors.lastname: Csako
authors.forename: Rene
authors.initials: R
authors.lastname: Costello
authors.forename: Frank
authors.initials: F
authors.lastname: Pucino
mesh_terms: D000328:Adult; D000368:Aged; D001055:Apolipoproteins B / Q000097:blood; D001823:Body Composition / Q000187:drug effects; D015519:Bone Density / Q000187:drug effects; D002784:Cholesterol / Q000097:blood; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000097:blood / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D011788:Quality of Life; D013963:Thyroid Hormones / Q000097:blood; D013974:Thyroxine / Q000008:administration & dosage / Q000627:therapeutic use*; D016896:Treatment Outcome; D014284:Triiodothyronine / Q000008:administration & dosage / Q000627:therapeutic use*
chemical_list: D001055:Apolipoproteins B; D013963:Thyroid Hormones; D014284:Triiodothyronine; D002784:Cholesterol; D013974:Thyroxine