title: Influence of human body composition on serum peak thyrotropin (TSH) after recombinant human TSH administration in patients with differentiated thyroid carcinoma.
abstract: OBJECTIVE
  In this study, we evaluated the influence of height, weight, body mass index (BMI), body surface area, and body composition [total lean body mass (LBM) and fat body mass] on serum peak TSH levels obtained after recombinant human (rh)TSH. Furthermore, to verify whether the serum peak TSH influenced the efficacy of radioiodine ((131)I), we compared the rate of thyroid remnant ablation according to the patients' BMI.
  
  
  METHODS
  We studied 105 patients with differentiated thyroid carcinoma who underwent rhTSH stimulation test. Serum TSH measurements were performed before and 24, 48, and 72 h after rhTSH administration. We also compared the rate of thyroid remnant ablation among 70 differentiated thyroid carcinoma patients with different BMI.
  
  
  RESULTS
  The serum peak TSH after rhTSH was significantly lower in overweight and obese subjects compared with normal-weight subjects (92.1 +/- 41.8, 82.4 +/- 24.2, and 112.7 +/- 46.3 microU/ml, respectively; P = 0.01) and in males compared with females (74.6 +/- 22.3 and 105.0 +/- 43.0 microU/ml, respectively; P = 0.0002). By univariate analysis, serum peak TSH was negatively related to weight, height, body surface area, BMI, LBM, and fat body mass, but only LBM was independently associated with serum peak TSH levels. Although it was confirmed that overweight and obese patients had a lower serum peak TSH, the rate of ablation did not differ among normal-weight, overweight, and obese patients.
  
  
  CONCLUSIONS
  With this study we demonstrated that LBM is the only parameter independently associated with serum peak TSH after rhTSH administration. However, the serum peak TSH does not influence the rate of (131)I remnant ablation.
authors.affiliation: Department of Endocrinology and Metabolism, University of Pisa, Via Paradisa 2, 56124 Pisa, Italy.
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Castagna
authors.forename: Aldo
authors.initials: A
authors.lastname: Pinchera
authors.forename: Alessandro
authors.initials: A
authors.lastname: Marsili
authors.forename: Monica
authors.initials: M
authors.lastname: Giannetti
authors.forename: Eleonora
authors.initials: E
authors.lastname: Molinaro
authors.forename: Paola
authors.initials: P
authors.lastname: Fierabracci
authors.forename: Lucia
authors.initials: L
authors.lastname: Grasso
authors.forename: Furio
authors.initials: F
authors.lastname: Pacini
authors.forename: Ferruccio
authors.initials: F
authors.lastname: Santini
authors.forename: Rossella
authors.initials: R
authors.lastname: Elisei
mesh_terms: D001823:Body Composition; D015992:Body Mass Index; D005260:Female; D006801:Humans; D008297:Male; D009765:Obesity / Q000097:blood; D011994:Recombinant Proteins / Q000494:pharmacology; D013964:Thyroid Neoplasms / Q000097:blood*; D013972:Thyrotropin / Q000097:blood* / Q000494:pharmacology
chemical_list: D011994:Recombinant Proteins; D013972:Thyrotropin