Influence of human body composition on serum peak thyrotropin (TSH) after recombinant human TSH administration in patients with differentiated thyroid carcinoma.
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.
Castagna
Maria Grazia
MG
Department of Endocrinology and Metabolism, University of Pisa, Via Paradisa 2, 56124 Pisa, Italy.
Pinchera
Aldo
A
Marsili
Alessandro
A
Giannetti
Monica
M
Molinaro
Eleonora
E
Fierabracci
Paola
P
Grasso
Lucia
L
Pacini
Furio
F
Santini
Ferruccio
F
Elisei
Rossella
R
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
D011994:Recombinant Proteins; D013972:Thyrotropin