title: [Should thyroxine treatment be discontinued for four weeks before I(131) thyroid ablation?].
abstract: BACKGROUND
  It is a usual practice to discontinue thyroxine treatment for four weeks before (131)I ablation. Symptoms of hypothyroidism usually occur during this time. Use of rhTSH is a helpful alternative in some cases, but problems of availability of this agent during 2012 will limit its use.
  
  
  METHODS
  Plasma TSH and FT4 levels were measured on days 7, 14, 21, and 28 after total thyroidectomy (12 patients) or discontinuation of thyroxine treatment (20 patients). A Mann-Whitney U test was used to compare quantitative variables, and a Chi-square test was used for nominal variables.
  
  
  RESULTS
  On day 14, TSH levels were 30μIU/mL of higher in 71% of patients (66% in the thyroidectomy group and 75% in the group discontinued thyroxine treatment). On day 21, almost all patients from both groups (91% in the thyroidectomy group and 100% in the group discontinued thyroxine treatment) had TSH levels of 30μIU/mL or higher. On day 14, most patients in both groups had FT4 levels below the normal range.
  
  
  CONCLUSIONS
  Discontinuation of thyroxine treatment for four weeks is not required. Fourteen days is an adequate time in most patients, and 21 days are sufficient in virtually all patients.
authors.affiliation: Servicio de Endocrinología y Nutrición, Complexo Hospitalario Universitario de Vigo, Vigo, Pontevedra, España.
authors.forename: Reyes
authors.initials: R
authors.lastname: Luna
authors.forename: Manuel
authors.initials: M
authors.lastname: Penín
authors.forename: Inés
authors.initials: I
authors.lastname: Seoane
authors.forename: Elías
authors.initials: E
authors.lastname: Alvarez
authors.forename: Regina
authors.initials: R
authors.lastname: Palmeiro
authors.forename: Ricardo
authors.initials: R
authors.lastname: García-Mayor
mesh_terms: D018263:Adenocarcinoma, Follicular / Q000097:blood / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery; D000328:Adult; D000368:Aged; D002291:Carcinoma, Papillary / Q000097:blood / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery; D016009:Chi-Square Distribution; D004334:Drug Administration Schedule; D005260:Female; D020249:Hormone Replacement Therapy; D006801:Humans; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics / Q000627:therapeutic use*; D008163:Luminescent Measurements; D008297:Male; D008875:Middle Aged; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics / Q000627:therapeutic use*; D018709:Statistics, Nonparametric; D013964:Thyroid Neoplasms / Q000097:blood / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery; D013965:Thyroidectomy; D013972:Thyrotropin / Q000097:blood / Q000378:metabolism*; D013974:Thyroxine / Q000009:adverse effects* / Q000097:blood / Q000627:therapeutic use
chemical_list: D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D013972:Thyrotropin; D013974:Thyroxine