Free thyroid hormone index, thyroid hormone/thyroxin-binding globulin ratio, triiodothyronine uptake, and thyroxin-binding globulin compared for diagnostic value regarding thyroid function.
The thyroid hormone/thyroxin-binding globulin (TBG) ratio and the free thyroid hormone index (FTI) were compared in 372 subjects classified according to age, sex, and biochemical and clinical findings. Age-related variations in thyroid function tests were investigated, as was the relationship between triiodothyronine uptake and TBG. Men, but not women, showed significant age-dependent changes in concentrations of thyroid hormones. FTI was as good as the thyroid hormone/TBG ratio in hyperthyroidism and was a better index of thyroid status in pregnancy, TBG deficiency, and hypothyroidism. In addition, the triiodothyronine uptake correlated extremely well with TBG (r = -0.95, p less than 0.001) and was very efficient in detecting decreased and significantly increased concentrations of TBG. I conclude that FTI is a better discriminator of functional status of the thyroid over a wider range of TBG values than is the thyroid hormone/TBG ratio. Further, the triiodothyronine uptake test produced diagnostic information equivalent to that of TBG estimation and thus should not be replaced in routine use.
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D005260:Female; D006801:Humans; D006980:Hyperthyroidism / Q000378:metabolism; D007037:Hypothyroidism / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D011247:Pregnancy; D012737:Sex Factors; D013961:Thyroid Gland / Q000503:physiopathology*; D013963:Thyroid Hormones / Q000097:blood*; D013975:Thyroxine-Binding Proteins / Q000032:analysis* / Q000378:metabolism; D014284:Triiodothyronine / Q000378:metabolism*
D013963:Thyroid Hormones; D013975:Thyroxine-Binding Proteins; D014284:Triiodothyronine