Radioimmunoassay of thyroxine-binding globulin: evaluation of a kit and diagnostic application

Associations between paraben exposure, thyroid capacity, homeostasis and pituitary thyrotropic function in the general Taiwanese: Taiwan Environmental Survey for Toxicants (TEST) 2013

Several studies have suggested that some endocrine disruptors such as synthetic phenols, parabens and phthalates may disrupt thyroid hormone signaling and associated negative feed-backs with the central hypothalamic-pituitary-thyroid (HPT) axis. Therefore, we investigated urinary paraben and blood thyroid hormone levels in the Taiwanese population. Our sample comprised 264 adults (aged 18-97 years) and 75 minors (aged 7-17 years) from Taiwan Environmental Survey for Toxicants 2013. Urinary levels of methylparaben (MeP), ethylparaben (EtP), propylparaben (PrP), and butylparaben (BuP) were assessed. Hormones of particular interest include: thyroid-stimulating hormone (TSH), triiodothyronine (T3), and thyroxine (T4). We sought integrated parameters to describe the transfer of thyroid hormones in homeostatic models. The geometric mean urinary paraben levels of the adults were higher than those of the minors (adults vs. minors; MeP: 383 vs. 62.4 ng/mL; PrP: 109 vs. 8.00 ng/mL; EtP: 39.5 vs. 2.38 ng/mL, and BuP: 6.36 vs. 2.13 ng/mL). In the male adults, we discovered that 0.253% (p = 0.032), 0.256% (p = 0.041) and 0.257% (p = 0.037) decreases in the TSH, TSH/T4 and TSH/FreeT4 ratio was associated with 1% EtP increases, respectively. In the female minors, 0.093% (p = 0.044), 0.072% (p = 0.047) and 0.156 (p = 0.004) increases in the TSH ratios were associated with a 1% MeP, EtP and BuP increase, respectively. Moreover, 0.151% (p = 0.008) and 0.177% (p = 0.001) increases in TSH/T4 and TSH/free T4 ratios were associated with a BuP 1% increase, respectively. Finally, EtP was positively associated with SPINA-GT (β: 15.66, p = 0.036) in the male adults. By contrast, EtP were positively associated with Jostel's TSH index and sTSHI (β: 0.072, p = 0.049; β: 0.107, p = 0.049) in the female minors. The Taiwanese population is commonly exposed to parabens, which can potentially lead to alteration of thyroid hormone homeostasis.

Triiodothyronine level and triiodothyronine/thyroxine ratio in HBeAg-positive chronic hepatitis patients treated with prednisolone withdrawal

Twenty patients with hepatitis B e antigen (HBeAg) -positive chronic hepatitis, who received 40 mg of prednisolone per day for three weeks followed by withdrawal, were studied for changes in alanine aminotransferase (ALT), triiodothyronine (T3), thyroxine (T4), and hepatitis B virus DNA polymerase (HBV-DNAp) levels determined before and during prednisolone treatment and after its withdrawal. A decreased HBV-DNAp level of less than 100 cpm/ml three to five weeks after withdrawal was considered a sign of efficacy and was shown in 10 patients (50%). Significant differences were found between ALT levels, between T3 levels, and between the T3/T4 ratios assayed in the third and fourth weeks in total (P less than 0.02) and in the group in which efficacy was demonstrated (P less than 0.01). The T3/T4 ratio in the third week in the effectively treated group was significantly less than that in the noneffectively treated group (P less than 0.05). Prednisolone withdrawal effective for HBV-DNAp was shown in the patients with a decreased T3 level and the T3/T4 ratio at the third week and an increase in the ATL level after the withdrawal. The ALT level increased after the T3 level decreased. Changes in the T3 level or the T3/T4 ratio represent a marker for effectiveness of prednisolone withdrawal and for determination of combination therapy after steroid withdrawal.

Thyroxine and thyroxine-binding globulin: discriminant formulae for the separation of the diagnostic classes of thyroid function

The biochemical classification of thyroid functional status is often accomplished by the use of the thyroxine to thyroxine-binding globulin (T4:TBG) ratio. It has recently been shown, however, that the reference range of the T4:TBG ratio varies with the concentration of TBG. This makes the T4:TBG ratio an unwieldy diagnostic index. A more accurate and economical way to define thyroid function using T4 and TBG measurements is by linear discriminant formulae. This is so because T4 varies linearly with TBG at the T4 reference limits over a wide range of TBG concentrations. Using the T4 reference ranges established by Attwood and Atkin (Ann Clin Biochem 1982; 19: 101-3), the following formulae are obtained: T4 (nmol/l)--4.05 TBG (mg/l) greater than 94.5 indicates hyperthyroidism; T4 (nmol/l)--2.72 TBG (mg/l) less than 23.8 identifies hypothyroidism.

A ligand-binding assay for thyroxine-binding globulin based on polyethylene glycol separation

A simple ligand-binding assay for thyroxine-binding globulin (TBG) is described. The method depends on the partition of labelled thyroxine between bovine serum albumin and TBG. Differentiation between labelled thyroxine bound to TBG and bovine serum albumin is achieved by the addition of excess TBG antiserum and subsequent precipitation with polyethylene glycol. The results are compared with the Corning Immophase kit method for TBG.