title: Weight Loss and Variation of Levothyroxine Requirements in Hypothyroid Obese Patients After Bariatric Surgery.
abstract: BACKGROUND
  Obesity and hypothyroidism are both common disorders within the general population. Obese hypothyroid subjects require higher doses of levothyroxine (LT4) compared with normal weight individuals. Previous studies on the effects of bariatric surgery on LT4 dose requirements in hypothyroid subjects have provided conflicting results. The aim of this study was to evaluate the LT4 requirements in a group of obese subjects with acquired hypothyroidism, before and after weight loss achieved by bariatric surgery.
  
  
  METHODS
  Ninety-three obese hypothyroid subjects (mean age = 48 ± 9 years; mean body mass index = 45.9 ± 5.6 kg/m(2)), were evaluated before and 28 ± 8 months after bariatric surgery. Changes in the LT4 dose, anthropometric measures, and hormone values were evaluated. In 20 patients, data of body composition, assessed by dual energy X-ray absorptiometry, were also analyzed.
  
  
  RESULTS
  On average, after weight loss, a significant reduction of the total dose of LT4 was documented (from 130.6 ± 48.5 to 116.2 ± 38.6 μg/day; p < 0.001). The LT4 dose had to be reduced in 47 patients, was unchanged in 34, and had to be increased in 12 patients affected by autoimmune thyroiditis. Reduction of the LT4 dose was proportional to reduction of the lean body mass.
  
  
  CONCLUSIONS
  The weight loss achieved with modern surgical bariatric procedures is associated with a reduction of LT4 requirements in most hypothyroid subjects, which appears to be related to a decrease of the lean body mass. Occasionally, a concurrent decline of residual thyroid function, as it occurs in autoimmune thyroiditis, can counteract this phenomenon and eventually produce an increase of LT4 needs. It is believed that during the weight loss phase that follows bariatric surgery, there is no need for preventive adjustments of the LT4 dose, but serum thyroid hormones and thyrotropin should be periodically monitored in order to detect possible variations of LT4 requirements and to allow proper corrections of the therapy.
authors.affiliation: Obesity Center, Endocrinology Unit 1, University Hospital of Pisa , Pisa, Italy .
authors.forename: Paola
authors.initials: P
authors.lastname: Fierabracci
authors.affiliation: Obesity Center, Endocrinology Unit 1, University Hospital of Pisa , Pisa, Italy .
authors.forename: Silvia
authors.initials: S
authors.lastname: Martinelli
authors.affiliation: Obesity Center, Endocrinology Unit 1, University Hospital of Pisa , Pisa, Italy .
authors.forename: Anna
authors.initials: A
authors.lastname: Tamberi
authors.affiliation: Obesity Center, Endocrinology Unit 1, University Hospital of Pisa , Pisa, Italy .
authors.forename: Paolo
authors.initials: P
authors.lastname: Piaggi
authors.affiliation: Obesity Center, Endocrinology Unit 1, University Hospital of Pisa , Pisa, Italy .
authors.forename: Alessio
authors.initials: A
authors.lastname: Basolo
authors.affiliation: Obesity Center, Endocrinology Unit 1, University Hospital of Pisa , Pisa, Italy .
authors.forename: Caterina
authors.initials: C
authors.lastname: Pelosini
authors.affiliation: Obesity Center, Endocrinology Unit 1, University Hospital of Pisa , Pisa, Italy .
authors.forename: Ilaria
authors.initials: I
authors.lastname: Ricco
authors.affiliation: Obesity Center, Endocrinology Unit 1, University Hospital of Pisa , Pisa, Italy .
authors.forename: Silvia
authors.initials: S
authors.lastname: Magno
authors.affiliation: Obesity Center, Endocrinology Unit 1, University Hospital of Pisa , Pisa, Italy .
authors.forename: Giorgia
authors.initials: G
authors.lastname: Querci
authors.affiliation: Obesity Center, Endocrinology Unit 1, University Hospital of Pisa , Pisa, Italy .
authors.forename: Giovanni
authors.initials: G
authors.lastname: Ceccarini
authors.affiliation: Obesity Center, Endocrinology Unit 1, University Hospital of Pisa , Pisa, Italy .
authors.forename: Giovanna
authors.initials: G
authors.lastname: Scartabelli
authors.affiliation: Obesity Center, Endocrinology Unit 1, University Hospital of Pisa , Pisa, Italy .
authors.forename: Guido
authors.initials: G
authors.lastname: Salvetti
authors.affiliation: Obesity Center, Endocrinology Unit 1, University Hospital of Pisa , Pisa, Italy .
authors.forename: Paolo
authors.initials: P
authors.lastname: Vitti
authors.affiliation: Obesity Center, Endocrinology Unit 1, University Hospital of Pisa , Pisa, Italy .
authors.forename: Ferruccio
authors.initials: F
authors.lastname: Santini
mesh_terms: D000328:Adult; D000886:Anthropometry; D050110:Bariatric Surgery; D015992:Body Mass Index; D001835:Body Weight / Q000187:drug effects*; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000150:complications* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications* / Q000601:surgery*; D012189:Retrospective Studies; D013974:Thyroxine / Q000008:administration & dosage*; D016896:Treatment Outcome; D015431:Weight Loss
chemical_list: D013974:Thyroxine