(d) USD, usual standard deviation; SCL, significant change limit; TBG,
thyroid-binding globulin; [TT.sub.4], total thyroxine; B2M, [[beta].sub.2]-microglobulin; DHEA-S[O.sub.4], dihydroepiandrostendione sulfate; GH, growth hormone; SHBG, sex hormone-binding globulin; TSH, thyroid-stimulating hormone; FT4, free thyroxine.
Levels of
thyroid-binding globulin (TBG) increase during pregnancy because of decreased clearance and increased estrogen effect on the liver.
The increase in
thyroid-binding globulin in pregnancy causes a rise in total thyroxine and triiodothyronine.[9] This is associated with a decrease in FT4, although the values usually do not drop below normal.[10] In the euthyroid patient who has a normally responsive thyroid, the TSH does not rise outside the normal range.
Thyroid and related growth hormones were measured using radioimmunoassay methods, including triiodothyronine ([T.sub.3]), thyroxine ([T.sub.4]), thyroid-stimulating hormone (TSH; thyrotropin), free [T.sub.4] (F[T.sub.4]), [T.sub.3] uptake,
thyroid-binding globulin (TBG), insulin-like growth factor (IGF)-1, and IGF-binding globulin-3 (BP3).
Increase in
thyroid-binding globulin. Thyroid hormones are transported in serum bound to three proteins: thyroxine-binding globulin (TBG), transthyretin, and albumin.
*
Thyroid-Binding Globulin. Drugs that increase TBG levels and thereby cause a 20%-30% increase in total [T.sub.4] and [T.sub.3] levels include the estrogens in oral contraceptives and hormone replacement therapy, tamoxifen, methadone, heroin, and the chemotherapeutic drugs mitotane and fluorouracil.
Thus,
thyroid-binding globulin (TBG) levels rose in cord blood with increased maternal PCB exposure.
Differences in [T.sub.4] are consistent with stimulatory and suppressive effects of estrogen and androgen on
thyroid-binding globulin serum concentration (26).
All patients had normal concentrations of
thyroid-binding globulin, a negative screen for familial dysalbuminemic hyperthyroxinemia, and no anti-[T.sub.4] and anti-[T.sub.3] antibodies.
[10,11] Thyroid dysfunction can be associated with proteinuria, which [12] results in increased excretion of thyroxine and
thyroid-binding globulins.
