Endocrine disruptors and the thyroid gland--a combined in vitro and in vivo analysis of potential new biomarkers.
BACKGROUND
There is growing evidence that, in addition to the reproductive system, the hypothalamic-pituitary-thyroid axis is a target of endocrine-disrupting compounds (EDCs). However, this is not reflected adequately in current screening and assessment procedures for endocrine activity that to date determine only general parameters of thyroid function.


OBJECTIVE
We used several in vitro and ex vivo assays in an attempt to identify suitable biomarkers for antithyroid action testing a selected panel of putative EDCs.


RESULTS
In vitro we detected stimulation or inhibition of iodide uptake into FRTL-5 rat thyroid cells, inhibition of thyroid hormone binding to transthyretin, agonistic or antagonistic effects in a thyroid hormone receptor-dependent reporter assay, and inhibition of thyroid peroxidase using a novel assay system based on human recombinant thyroperoxidase that might be suitable for routine screening for potential EDCs. In rats, chronic application of several EDCs led to changes in thyroid morphology, alterations of thyrotropin and thyroid hormone serum levels as well as alterations in peripheral thyroid hormone-regulated end points such as malic enzyme and type I 5'-deiodinase activity.


CONCLUSIONS
As the effects of EDCs do not reflect classic mechanisms of hormone-dependent regulation and feedback, we believe multitarget and multimodal actions of EDCs affect the hypothalamic-pituitary-thyroid axis. These complex effects require a diverse approach for screening, evaluation, and risk assessment of potential antithyroid compounds. This approach involves novel in vitro or cell-based screening assays in order to assess thyroid hormone synthesis, transport, metabolism, and action as well as in vivo assays to measure thyroid hormone-regulated tissue-specific and developmental end points in animals.
Schmutzler
Cornelia
C
Institut für Experimentelle Endokrinologie, Charité - Universitätsmedizin Berlin, Berlin, Germany. cornelia.schmutzler@charite.de
Gotthardt
Inka
I
Hofmann
Peter J
PJ
Radovic
Branislav
B
Kovacs
Gabor
G
Stemmler
Luise
L
Nobis
Inga
I
Bacinski
Anja
A
Mentrup
Birgit
B
Ambrugger
Petra
P
Grüters
Annette
A
Malendowicz
Ludwik K
LK
Christoffel
Julie
J
Jarry
Hubertus
H
Seidlovà-Wuttke
Dana
D
Wuttke
Wolfgang
W
Köhrle
Josef
J
D000818:Animals; D015415:Biomarkers; D002460:Cell Line; D052244:Endocrine Disruptors / Q000633:toxicity*; D005260:Female; D066298:In Vitro Techniques; D007453:Iodide Peroxidase / Q000187:drug effects / Q000378:metabolism; D007455:Iodine / Q000378:metabolism; D008291:Malate Dehydrogenase / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013961:Thyroid Gland / Q000187:drug effects* / Q000378:metabolism; D013963:Thyroid Hormones / Q000378:metabolism*; D013972:Thyrotropin / Q000097:blood / Q000187:drug effects
D015415:Biomarkers; D052244:Endocrine Disruptors; D013963:Thyroid Hormones; D013972:Thyrotropin; D007455:Iodine; D008291:Malate Dehydrogenase; C109812:iodothyronine deiodinase type I; D007453:Iodide Peroxidase