title: Short-term overt hypothyroidism induces discrete diastolic dysfunction in patients treated for differentiated thyroid carcinoma.
abstract: BACKGROUND
  Thyroid hormone has important effects on the cardiovascular system. The consequences of episodes of acute hypothyroidism on cardiac function have been investigated in only a few studies, and their results are inconclusive. Our objective was to investigate the effects of acute hypothyroidism on cardiac function in patients with iatrogenically induced subclinical hyperthyroidism after treatment for differentiated thyroid carcinoma.
  
  
  METHODS
  Fourteen patients with a history of differentiated thyroid carcinoma on thyroid-stimulating hormone (TSH)-suppressive thyroxine replacement therapy were studied. We assessed cardiac function before, and 1 and 4 weeks after withdrawal of thyroxine substitution. We measured serum levels of free thyroxine, triiodothyronine and TSH and used a new sophisticated Doppler echocardiography technique, tissue Doppler imaging (TDI), to assess detailed and quantitative assessment of systolic and diastolic cardiac function. Echocardiographic parameters in patients were compared to controls.
  
  
  RESULTS
  Compared to controls, patients had higher left ventricular mass and wall thickness and decreased diastolic function during TSH-suppressive l-thyroxine substitution therapy. Thyroxine withdrawal resulted in a decrease in both early (E) and late (A) diastolic mitral inflow velocities, without impact on E/A ratio. Using TDI, late diastolic velocity (A') decreased without impact on E'/A' ratio. Left ventricular dimensions, wall thickness and mass did not change during thyroxine withdrawal.
  
  
  CONCLUSIONS
  Subclinical hyperthyroidism is accompanied by diastolic dysfunction. Subsequent acute hypothyroidism induces only subtle changes in diastolic function.
authors.affiliation: Leiden University Medical Center, Leiden, The Netherlands. h.c.hoftijzer@lumc.nl
authors.forename: H C
authors.initials: HC
authors.lastname: Hoftijzer
authors.forename: J J
authors.initials: JJ
authors.lastname: Bax
authors.forename: K A
authors.initials: KA
authors.lastname: Heemstra
authors.forename: G B
authors.initials: GB
authors.lastname: Bleeker
authors.forename: V
authors.initials: V
authors.lastname: Delgado
authors.forename: A A
authors.initials: AA
authors.lastname: van der Klaauw
authors.forename: J A
authors.initials: JA
authors.lastname: Romijn
authors.forename: J W A
authors.initials: JW
authors.lastname: Smit
authors.forename: E P M
authors.initials: EP
authors.lastname: Corssmit
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003971:Diastole; D015150:Echocardiography, Doppler; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000150:complications*; D008297:Male; D008875:Middle Aged; D013960:Thyroid Function Tests; D013964:Thyroid Neoplasms / Q000188:drug therapy*; D013972:Thyrotropin / Q000627:therapeutic use*; D013997:Time Factors; D018487:Ventricular Dysfunction, Left / Q000209:etiology*; D055815:Young Adult
chemical_list: D013972:Thyrotropin