title: Long-term follow-up of antithyroid peroxidase antibodies in patients with chronic autoimmune thyroiditis (Hashimoto's thyroiditis) treated with levothyroxine.
abstract: BACKGROUND
  A number of studies show that the serum levels of antithyroid peroxidase antibodies (TPO-Ab) in patients with Hashimoto's thyroiditis decline during levothyroxine treatment, but do not provide quantitative data or report the fraction of patients in whom test for TPO-Ab became negative ("normalization percentage"). The objective of the present study was to provide this information.
  
  
  METHODS
  This was a retrospective study of TPO-Ab concentrations in 36 women and 2 men (mean age 51 +/- 16 years; range 19-81 years) with Hashimoto's thyroiditis as defined by the following criteria: elevated plasma TPO-Ab and typical hypoechogenicity of the thyroid in high-resolution sonography at first presentation or during follow-up and low pertechnetate uptake in thyroid scintigraphy. When first studied 17 women and 1 man were not yet taking levothyroxine. The remaining 20 patients were receiving levothyroxine. At initial examination 18 patients had serum thyroid-stimulating hormone (TSH) concentrations above normal. Results of up to eight (mean = 5.8) measurements obtained over a mean period of 50 months while patients were receiving levothyroxine were analyzed. In addition, serum TSH, free triiodothyronine (fT3), and free thyroxine (fT4) were measured, and ultrasound of the neck was performed at each follow-up examination.
  
  
  RESULTS
  In terms of TPO-Ab levels, 35 of 38 patients (92%) had a decrease, 2 patients had undulating levels, and 1 patient had an inverse hyperbolic increase in her TPO-Ab levels. In the 35 patients in whom there were decreasing TPO-Ab values, the mean of the first value was 4779 IU/mL with an SD of 4099 IU/mL. The mean decrease after 3 months was 8%, and after 1 year it was 45%. Five years after the first value, TPO-Ab levels were 1456 +/- 1219 IU/mL, a decrease of 70%. TPO-Ab levels became negative, < 100 IU/mL, in only six patients, a normalization percentage of 16%. There were no correlations between changes in thyroid volume and changes in TPO-Ab.
  
  
  CONCLUSIONS
  Serum TPO-Ab levels decline in most patients with Hashimoto's thyroiditis who are taking levothyroxine, but after a mean of 50 months, TPO-Ab became negative in only a minority of patients.
authors.affiliation: Department of Nuclear Medicine, University of Cologne, Cologne, Germany. matthias.schmidt@uni-koeln.de
authors.forename: Matthias
authors.initials: M
authors.lastname: Schmidt
authors.forename: Michael
authors.initials: M
authors.lastname: Voell
authors.forename: Ilka
authors.initials: I
authors.lastname: Rahlff
authors.forename: Markus
authors.initials: M
authors.lastname: Dietlein
authors.forename: Carsten
authors.initials: C
authors.lastname: Kobe
authors.forename: Michael
authors.initials: M
authors.lastname: Faust
authors.forename: Harald
authors.initials: H
authors.lastname: Schicha
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000888:Antibodies, Anti-Idiotypic / Q000097:blood* / Q000276:immunology; D004305:Dose-Response Relationship, Drug; D005260:Female; D005500:Follow-Up Studies; D050031:Hashimoto Disease / Q000097:blood / Q000188:drug therapy* / Q000276:immunology*; D006801:Humans; D007453:Iodide Peroxidase / Q000276:immunology*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood / Q000627:therapeutic use*; D013997:Time Factors; D014284:Triiodothyronine / Q000097:blood
chemical_list: D000888:Antibodies, Anti-Idiotypic; D014284:Triiodothyronine; D013972:Thyrotropin; D007453:Iodide Peroxidase; D013974:Thyroxine