Compound W, a 3,3'-diiodothyronine sulfate cross-reactive substance in serum from pregnant women--a potential marker for fetal thyroid function

Second-Trimester Placental and Thyroid Hormones Are Associated With Cognitive Development From Ages 1 to 3 Years

Adequate maternal thyroid hormone (TH) is necessary for fetal brain development. The role of placental human chorionic gonadotropin (hCG) in ensuring the production of TH is less well understood. The objective of the study was to evaluate 1) associations of placental hCG and its subunits, and maternal TH in the second trimester, and 2) the single and joint effects of TH and placental hormones on cognitive development and communication at ages 1 and 3 years. Fifty individuals (5%) were selected from the CANDLE (Conditions Affecting Neurocognitive Development and Early Learning) pregnancy cohort in Memphis, Tennessee, with recruitment from 2006 to 2011, to equally represent male and female fetuses. Participants were 68% Black and 32% White. Hormones measured were maternal thyroid (thyrotropin [TSH] and free thyroxine [FT4]) and placental hormones (hCG, its hyperglycosylated form [hCG-h], and free - [hCG] and -subunits [hCG]) in maternal serum (17-28 weeks). The primary outcome measurement was the Bayley Scales of Infant and Toddler Development. All forms of hCG were negatively associated with FT4 and not associated with TSH. hCG was associated with cognitive development at age 1 year and jointly interacted with TSH to predict cognitive development at age 3 years. This pilot study added insight into the thyrotropic actions of hCG in the second trimester, and into the significance of this mechanism for brain development. More research is warranted to elucidate differences between hCG, hCG, and hCG-h in relation to TH regulation and child brain function.

A Homogeneous Time-Resolved Fluorescence Immunoassay Method for the Measurement of Compound W

OBJECTIVE

Using compound W (a 3,3'-diiodothyronine sulfate [T2S] immuno-crossreactive material)-specific polyclonal antibodies and homogeneous time-resolved fluorescence immunoassay assay techniques (AlphaLISA) to establish an indirect competitive compound W (ICW) quantitative detection method.

METHOD

Photosensitive particles (donor beads) coated with compound W or T2S and rabbit anti-W antibody were incubated with biotinylated goat anti-rabbit antibody. This constitutes a detection system with streptavidin-coated acceptor particle. We have optimized the test conditions and evaluated the detection performance.

RESULTS

The sensitivity of the method was 5 pg/mL, and the detection range was 5 to 10 000 pg/mL. The intra-assay coefficient of variation averages <10% with stable reproducibility.

CONCLUSIONS

The ICW-AlphaLISA shows good stability and high sensitivity and can measure a wide range of compound W levels in extracts of maternal serum samples. This may have clinical application to screen congenital hypothyroidism in utero.

Thyroid Hormones and Derivatives: Endogenous Thyroid Hormones and Their Targets

More than a century after the discovery of L-Thyroxine, the main thyroid hormone secreted solely by the thyroid gland, several metabolites of this iodinated, tyrosine-derived ancestral hormone have been identified. These are utilized as hormones during development, differentiation, metamorphosis, and regulation of most biochemical reactions in vertebrates and their precursor species. Among those metabolites are the thyromimetically active 3,3',5-Triiodo-L-thyronine (T3) and 3,5-Diiodo-L-thronine, reverse-T3 (3,3',5'-Triiodo-L-thyronine) with still unclear function, the recently re-discovered thyronamines (e.g., 3-Iodo-thyronamine), which exert in part T3-antagonistic functions, the thyroacetic acids (e.g., Tetrac and Triac), as well as various sulfated or glucuronidated metabolites of this panel of iodinated signaling compounds. In the blood most of these hydrophobic metabolites are tightly bound to the serum distributor proteins thyroxine binding globulin (TBG), transthyretin (TTR), albumin or apolipoprotein B100. Cellular import and export of these charged, highly hydrophobic amino acid derivatives requires a number of cell-membrane transporters or facilitators such as MCT8 or MCT10 and members of the OATP and LAT families of transporters. Depending on their structure, the thyroid hormone metabolites exert their cellular action by binding and thus modulating the function of various receptors systems (e.g., ανβ3 integrin receptor and transient receptor potential channels (TRPM8) of the cell membrane), in part linked to intracellular downstream kinase signaling cascades, and several isoforms of membrane-associated, mitochondrial or nuclear thyroid hormone receptors (TR), which are members of the c-erbA family of ligand-modulated transcription factors. Intracellular deiodinase selenoenzymes, which obligatory are membrane integrated enzymes, ornithine decarboxylase and monoamine oxidases control local availability of biologically active thyroid hormone metabolites. Inactivation of thyroid hormone metabolites occurs mainly by deiodination, sulfation or glucuronidation, reactions which favor their renal or fecal elimination.

The classic pathways of thyroid hormone metabolism

Thyroid hormones (TH) are crucial for growth and development and play an important role in energy homeostasis. Although serum TH levels are relatively constant in the physiological state, TH bioavailability at the tissue and cellular level is dependent on local TH metabolism. Circulating TH produced by the thyroid can be metabolized by a number of different pathways resulting in 1) activation of TH 2) deactivation of TH or 3) excretion of TH and subsequent metabolites. These pathways play an essential role in determining local TH levels and action. The major classical pathways of TH metabolism are deiodination, sulfation, glucuronidation, and ether-link cleavage. This review provides an overview of these pathways, their relative contributions to TH levels in the serum and in various organs and the changes in these pathways elicited by fasting and illness.

3,3'-Diiodothyronine sulfate cross-reactive material (compound W) in human newborns

BACKGROUND

Thyrosulfoconjugation appears to facilitate fetal-to-maternal transfer of 3,3'-diiodothyronine-sulfate (T(2)S). Elevated maternal levels of T(2)S cross-reactive material (compound W) are found in humans, with higher levels found in venous cord blood than in arterial samples. These findings are consistent with the postulate that the placenta plays an essential role in compound W production.

METHODS

Serum compound W levels were measured by a T(2)S-specific radioimmunoassay in 60 serum samples from newborns with hyperbilirubinemia, age 1-30 d. In addition, 59 maternal serum samples, from day 1 to day 7 after uneventful deliveries, were studied.

RESULTS

As compared with day 1, at day 5, the mean (±SE) compound W level fell to 43.5 ± 6.8% (decay half-life (t(1/2)) = 4.12 d) and to 33.7 ± 4.6% (decay t(1/2) = 2.82 d) in the newborn and maternal groups, respectively. In the mothers, the level continued to decline along the same slope through day 7. In the newborns, however, the mean compound W level entered a slower phase of decay after the fifth day with a decay t(1/2) = 10.9 d.

CONCLUSION

Compound W is cleared at similar rates in newborn and postpartum maternal sera. This is consistent with the postulate that compound W is produced in the placenta.

Thyroid function and 3,3'-diiodothyronine sulfate cross-reactive substance (compound W) in maternal hyperthyroidism with antithyroid treatment

OBJECTIVE

To test whether the serial measurement of maternal levels of compound W, a 3,3'-diiodothyronine sulfate cross-reactive substance, can serve as a potential indicator of fetal thyroid function in pregnant women receiving antithyroid medication.

METHODS

Compound W was measured repeatedly in serum of pregnant women with hyperthyroidism treated with antithyroid medication. Free thyroxine levels of mothers and serum thyroid-stimulating hormone levels of 1-day-old neonates were analyzed by local clinical or state laboratories.

RESULTS

Use of minimal antithyroid medication impaired the progressive increase of compound W seen in euthyroid mothers during pregnancy. At term, depressed compound W levels in maternal serum were found in 7 of 22 pregnancies; in 1 case, maternal compound W was suppressed and newborn thyroid-stimulating hormone was elevated. Seven mothers with treated hyperthyroidism failed to show an increase in serum levels of compound W after midterm.

CONCLUSION

Normal progression of maternal serum compound W may be an index of normal fetal thyroid development in mothers with hyperthyroidism treated with necessary antithyroid medication.

3'-monoiodothyronine sulfate and Triac sulfate are thyroid hormone metabolites in developing sheep

We used novel 3'-monoiodothyronine sulfate (3'-T1S) and 3,3',5-triiodothyroacetic acid sulfate (TriacS) RIAs to characterize sulfation pathways in fetal thyroid hormone metabolism. 3'-T1S and TriacS levels were measured in serum samples obtained from fetal (n = 21, 94-145 d gestational age), newborn (NB, n = 5), and adult sheep (AD, n = 5) as well as from fetuses after total thyroidectomy (Tx), or sham-operated twin fetuses controls, conducted at gestational age 110-113 d (n = 5). Peak levels (expressed as ng/dL) of both 3'-T1S and TriacS occurred at 130 d gestation. These levels in fetuses were higher than those in NB and AD. In Tx fetuses, there was a significant decrease in the mean serum level of 3'-T1S, but not TriacS. The decrease in 3'-T1S in Tx is similar to that observed for thyroxine sulfate (T4S) and 3,3',5'-triiodothyronine sulfate (rT3S), whereas TriacS levels were not altered in the hypothyroid state, similarly to 3,3',5-triiodothyronine sulfate (T3S). These data demonstrate that 3'-T1S and TriacS are normal thyroid hormone metabolites in ovine serum and that TriacS is likely derived from T3S or from the same precursor(s) as T3S.