title: Thyroid function is more strongly associated with body impedance than anthropometry in healthy subjects.
abstract: Since fat-free tissues are responsible for 95% of basal energy expenditure, fat-free mass is expected to be a better determinant of thyroid size and function than anthropometry. We tested the hypothesis that fat-free tissues as qualitatively determined by body resistance (R) at 50 kHz are more strongly associated with TSH than anthropometric indicators in healthy subjects. A number of 78 euthyroid adults of both sexes were consecutively studied. R was the best single predictor of TSH (R2(adj)=0.65, p<0.0001). It explained 36% more variance than bw (R2(adj)=0.29, p<0.0001), the most accurate anthropometric predictor. Sex had no effect on the relationship between TSH, bioelectrical impedance analysis and anthropometry. After the contribution of R to TSH was taken into account, anthropometric indicators were not able to explain any additional part of TSH variance. We conclude that in healthy subjects, bioelectrical resistance is a better indicator of thyroid function than anthropometry, probably because of its more direct relationship with fat-free tissues. Further studies are needed to test whether this relationship holds in under- and over-weight subjects.
authors.affiliation: Division of Metabolic Diseases III, Istituto Auxologico Italiano, IRCCS, Piancavallo, Verbania, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Sartorio
authors.forename: S
authors.initials: S
authors.lastname: Ferrero
authors.forename: L
authors.initials: L
authors.lastname: Trecate
authors.forename: G
authors.initials: G
authors.lastname: Bedogni
mesh_terms: D000273:Adipose Tissue; D000328:Adult; D000886:Anthropometry; D001823:Body Composition; D015992:Body Mass Index; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012727:Sex Characteristics; D013961:Thyroid Gland / Q000502:physiology*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
chemical_list: D014284:Triiodothyronine; D013972:Thyrotropin; D013974:Thyroxine