title: Effects of thyroxine replacement on endothelial function and carotid artery intima-media thickness in female patients with mild subclinical hypothyroidism.
abstract: BACKGROUND
  Previous studies have suggested an association between subclinical hypothyroidism and coronary artery disease that could be related to changes in serum lipids or endothelial dysfunction.
  
  
  METHODS
  Thirty-two female subclinical hypothyroidism patients were randomly assigned to 12 months of L-thyroxine replacement or no treatment. Endothelial function was measured by the flow-mediated vasodilatation of the brachial artery, as well as mean carotid artery intima-media thickness, and lipid profiles were studied at baseline and after 12 months of follow-up.
  
  
  RESULTS
  The mean ( ± SD) serum thyroid-stimulating hormone levels in the L-thyroxine replacement and control groups were 6.09 ± 1.32 and 6.27 ± 1.39 μUI/ml, respectively. No relationship between carotid artery intima-media thickness or brachial flow-mediated vasodilatation and free T4 and serum thyroid-stimulating hormone was found. The median L-T4 dose was 44.23 ± 18.13 μg/day. After 12 months, there was a significant decrease in the flow-mediated vasodilatation in the subclinical hypothyroidism control group (before: 17.33 ± 7.88 to after: 13.1 ± 4.75%, p =0.03), but there were no significant differences in flow-mediated vasodilatation in the L-thyroxine treated group (before: 16.81 ± 7.0 to after: 18.52 ± 7.44%, p = 0.39). We did not find any significant change in mean carotid intimamedia thickness after 12 months of L-thyroxine treatment.
  
  
  CONCLUSIONS
  Replacement therapy prevents a decline in flow-mediated vasodilatation with continuation of the subclinical hypothyroidism state. Large prospective multicenter placebo-controlled trials are necessary to investigate endothelial physiology further in subclinical hypothyroidism patients and to define the role of L-thyroxine therapy in improving endothelial function in these patients.
authors.affiliation: Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil. mdcabral@globo.com
authors.forename: Monica Dias
authors.initials: MD
authors.lastname: Cabral
authors.forename: Patricia
authors.initials: P
authors.lastname: Teixeira
authors.forename: Debora
authors.initials: D
authors.lastname: Soares
authors.forename: Sandra
authors.initials: S
authors.lastname: Leite
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Salles
authors.forename: Mario
authors.initials: M
authors.lastname: Waisman
mesh_terms: D000328:Adult; D059168:Carotid Intima-Media Thickness; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology; D005260:Female; D005500:Follow-Up Studies; D020249:Hormone Replacement Therapy; D006801:Humans; D007037:Hypothyroidism / Q000097:blood / Q000188:drug therapy* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012039:Regional Blood Flow / Q000187:drug effects; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000627:therapeutic use*; D014664:Vasodilation / Q000502:physiology
chemical_list: D013972:Thyrotropin; D013974:Thyroxine