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Event: 279

Key Event Title

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Thyroperoxidase, Inhibition

Short name
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Thyroperoxidase, Inhibition
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Biological Context

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Level of Biological Organization

Cell term

The location/biological environment in which the event takes place.The biological context describes the location/biological environment in which the event takes place.  For molecular/cellular events this would include the cellular context (if known), organ context, and species/life stage/sex for which the event is relevant. For tissue/organ events cellular context is not applicable.  For individual/population events, the organ context is not applicable.  Further information on Event Components and Biological Context may be viewed on the attached pdf. More help
Cell term
thyroid follicular cell

Organ term

The location/biological environment in which the event takes place.The biological context describes the location/biological environment in which the event takes place.  For molecular/cellular events this would include the cellular context (if known), organ context, and species/life stage/sex for which the event is relevant. For tissue/organ events cellular context is not applicable.  For individual/population events, the organ context is not applicable.  Further information on Event Components and Biological Context may be viewed on the attached pdf. More help
Organ term
thyroid follicle

Key Event Components

The KE, as defined by a set structured ontology terms consisting of a biological process, object, and action with each term originating from one of 14 biological ontologies (Ives, et al., 2017; Biological process describes dynamics of the underlying biological system (e.g., receptor signalling).Biological process describes dynamics of the underlying biological system (e.g., receptor signaling).  The biological object is the subject of the perturbation (e.g., a specific biological receptor that is activated or inhibited). Action represents the direction of perturbation of this system (generally increased or decreased; e.g., ‘decreased’ in the case of a receptor that is inhibited to indicate a decrease in the signaling by that receptor).  Note that when editing Event Components, clicking an existing Event Component from the Suggestions menu will autopopulate these fields, along with their source ID and description.  To clear any fields before submitting the event component, use the 'Clear process,' 'Clear object,' or 'Clear action' buttons.  If a desired term does not exist, a new term request may be made via Term Requests.  Event components may not be edited; to edit an event component, remove the existing event component and create a new one using the terms that you wish to add.  Further information on Event Components and Biological Context may be viewed on the attached pdf. More help
Process Object Action
iodide peroxidase activity thyroid peroxidase decreased

Key Event Overview

AOPs Including This Key Event

All of the AOPs that are linked to this KE will automatically be listed in this subsection. This table can be particularly useful for derivation of AOP networks including the KE.Clicking on the name of the AOP will bring you to the individual page for that AOP. More help
AOP Name Role of event in AOP Point of Contact Author Status OECD Status
TPO Inhibition and Altered Neurodevelopment MolecularInitiatingEvent Evgeniia Kazymova (send email) Open for citation & comment WPHA/WNT Endorsed
Thyroid peroxidase- follicular adenoma/carcinoma MolecularInitiatingEvent Brendan Ferreri-Hanberry (send email) Under Development: Contributions and Comments Welcome
TPOi anterior swim bladder MolecularInitiatingEvent Evgeniia Kazymova (send email) Under Development: Contributions and Comments Welcome WPHA/WNT Endorsed
TPO inhib alters metamorphosis MolecularInitiatingEvent Brendan Ferreri-Hanberry (send email) Under Development: Contributions and Comments Welcome
TPO inhibition and impaired fertility MolecularInitiatingEvent Cataia Ives (send email) Open for comment. Do not cite Under Development
TPOi retinal layer structure MolecularInitiatingEvent Allie Always (send email) Open for citation & comment Under Review
TPOi eye size MolecularInitiatingEvent Evgeniia Kazymova (send email) Under development: Not open for comment. Do not cite Under Development
TPOi photoreceptor patterning MolecularInitiatingEvent Cataia Ives (send email) Under development: Not open for comment. Do not cite Under Development
TPO inhibition, thyroid, heterotopia, developmental neurotoxicity MolecularInitiatingEvent Allie Always (send email) Under development: Not open for comment. Do not cite

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) that help to define the biological applicability domain of the KE.In many cases, individual species identified in these structured fields will be those for which the strongest evidence used in constructing the AOP was available in relation to this KE. More help
Term Scientific Term Evidence Link
rat Rattus norvegicus High NCBI
humans Homo sapiens High NCBI
pigs Sus scrofa High NCBI
Xenopus laevis Xenopus laevis High NCBI
chicken Gallus gallus High NCBI
zebrafish Danio rerio High NCBI
fathead minnow Pimephales promelas High NCBI
mouse Mus musculus NCBI

Life Stages

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Life stage Evidence
All life stages High

Sex Applicability

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Term Evidence
Female High
Male High

Key Event Description

A description of the biological state being observed or measured, the biological compartment in which it is measured, and its general role in the biology should be provided. More help

Thyroperoxidase (TPO) is a heme-containing apical membrane protein within the follicular lumen of thyrocytes that acts as the enzymatic catalyst for thyroid hormone (TH) synthesis. TPO catalyzes several reactions in the thyroid gland, including: the oxidation of iodide; nonspecific iodination of tyrosyl residues of thyroglobulin (Tg); and the coupling of iodotyrosyls to produce Tg-bound monoiodotyrosine (MIT) and diiodotyrosine (DIT) (Divi et al., 1997; Kessler et al., 2008; Ruf et al., 2006; Taurog et al., 1996). The outcome of TPO inhibition is decreased synthesis of thyroxine (T4) and triiodothyronine (T3), a decrease in release of these hormones from the gland into circulation, and unless compensated, a consequent decrease in systemic concentrations of T4, and possibly T3. The primary product of TPO-catalyzed TH synthesis is T4 (Taurog et al., 1996; Zoeller et al., 2007) that would be peripherally or centrally deiodinated to T3.

It is important to note that TPO is a complex enzyme that has two catalytic cycles and is capable of iodinating multiple species (Divi et al., 1997). Alterations in all of these events are not covered by some of the commonly used assays that measure “TPO inhibition” (e.g., guaiacol and AmplexUltraRed, see below). Ususally just the first step of this series of events is covered by assays that measure TPO inhibition. Therefore, in the context of this AOP we are using TPO inhibition not in the classical sense, but instead to refer to the empirical data derived from the assays commonly used to investigate environmental chemicals. Therefore, in the context of this AOP we are using TPO inhibition not in the classical sense, but instead to refer to the empirical data derived from the assays commonly used to investigate environmental chemicals.

Figure 1      illustrates the enzymatic and nonenzymatic reactions mediated by TPO that result in the synthesis of thyroxine (T4) .

Inhibition of TPO can be reversible, with transient interaction between the enzyme and the chemical, or irreversible, whereby suicide substrates permanently inactivate the enzyme. Reversible and irreversible (isoflavones such as genistein) TPO inhibition may be determined by the chemical structure, may be concentration dependent, or may be influenced by other conditions, including the availability of iodine (Doerge and Chang, 2002).

The ontogeny of TPO has been determined using both direct and indirect evidence in mammals.  Available evidence suggests the 11th to 12th fetal week as the beginning of functional TPO in humans. In rodents, TPO function begins late in the second fetal week, with the first evidence of T4 secretion on gestational day 17 (Remy et al., 1980). Thyroid-specific genes appear in the thyroid gland according to a specific temporal pattern; thyroglobulin (Tg), TPO (Tpo), and TSH receptor (Tshr) genes are expressed by gestational day 14 in rats, and the sodium iodide symporter, NIS (Nis), is expressed by gestational day 16 in rats. Maturation to adult function is thought to occur within a few weeks after parturition in rats and mice, and within the first few months in neonatal humans (Santisteban and Bernal, 2005).  Tg is first detected in human fetuses starting at 5th week of gestation and rises throughout gestation (Thorpe-Beeston et al., 1992), but iodine trapping and T4 production does not occur until around 10-12 weeks. Also, the dimerization of Tg, a characteristic of adult TH storage, is not found until much later in human gestation (Pintar, 2000). In rats, Tg immunoreactivity does not appear until day 15 of gestation (Fukiishi et al., 1982; Brown et al., 2000). The vast majority of research and knowledge on Tg is from mammals, although genomic orthologs are known for a variety of other species (Holzer et al., 2016). It is important to note that prior to the onset of fetal thyroid function, THs are still required by the developing fetus which until that time relies solely on maternal sources. Chemical-induced TPO inhibition can affect synthesis in the maternal gland and in the fetal gland.

The components of the TH system responsible for TH synthesis are highly conserved across vertebrates. In fish and amphibians TPO and NIS inhibition result in an expected decrease of TH synthesis (Hornung et al., 2010; Tietge et al., 2013; Nelson et al., 2016; Stinckens et al., 2016; Stinckens et al., 2020) like in mammals. Although the TH system is highly conserved across vertebrates, there are some taxon-specific considerations.

Zebrafish and fathead minnows are oviparous fish species in which maternal THs are transferred to the eggs and regulate early embryonic developmental processes during external (versus intra-uterine in mammals) development (Power et al., 2001; Campinho et al., 2014; Ruuskanen and Hsu, 2018) until embryonic TH synthesis is initiated. Maternal transfer of THs to the eggs has been demonstrated in zebrafish (Walpita et al., 2007; Chang et al., 2012) and fathead minnows (Crane et al., 2004; Nelson et al., 2016).

Inhibition of TPO can only occur after activation of embryonic TH synthesis mediated by TPO. Endogenous transcription profiles of thyroid-related genes in zebrafish and fathead minnow showed that mRNA coding for TPO is maternally transferred in relatively high amounts with subsequent mRNA degradation followed by initiation of embryonic transcription around hatching (Vergauwen et al., 2018).

How It Is Measured or Detected

A description of the type(s) of measurements that can be employed to evaluate the KE and the relative level of scientific confidence in those measurements.These can range from citation of specific validated test guidelines, citation of specific methods published in the peer reviewed literature, or outlines of a general protocol or approach (e.g., a protein may be measured by ELISA). Do not provide detailed protocols. More help

There are no approved OECD or EPA guideline study protocols for measurement of TPO inhibition. However, there is an OECD scoping document on identification of chemicals that modulate TH signaling that provides details on a TPO assay (OECD, 2017). 

From the early 1960's, microsomal fractions prepared from porcine thyroid glands and isolated porcine follicles were used as a source of TPO for inhibition experiments (Taurog, 2005). Microsomes from human goiter samples (Vickers et al., 2012) and rat thyroid glands (Paul et al., 2013; 2014; Paul-Friedman et al., 2016) have also been used as a source of TPO.

TPO activity has been measured for decades via indirect assessment by kinetic measurement of the oxidation of guaiacol (Chang & Doerge 2000; Hornung et al., 2010; Schmutzler et al., 2007).  This method is a low-throughput assay due to the very rapid kinetics of the guaiacol oxidation reaction. More recently, higher-throughput methods using commercial fluorescent and luminescent substrates with rodent, porcine, and human microsomal TPO have been developed (Vickers et al., 2012; Paul et al., 2013; 2014; Kaczur et al., 1997). This assay substitutes a pre-fluorescent substrate (Amplex UltraRed) for guaiacol, that when incubated with a source of peroxidase and excess hydrogen peroxidase, results in a stable fluorescent product proportional to TPO activity (Vickers et al., 2012). The stability of the fluorescent reaction product allows this assay to be used in a higher throughput format (Paul-Friedman et al., 2016). This approach is appropriate for high-throughput screening but does not elucidate the specific mechanism by which a chemical may inhibit TPO (Paul-Friedman et al., 2016), and as with most in vitro assays, is subject to various sources of assay interference (Thorne et al., 2010). Recombinant sources of TPO have also been used (e.g. Schmutzler et al., 2007; Dong et al., 2020)

HPLC has been used to measure the activity of TPO via formation of the precursors monoiodotyrosine (MIT), diiodotyrosine (DIT), and both T3 and T4, in a reaction mixture containing TPO, or a surrogate enzyme such as lactoperoxidase (Divi & Doerge 1994). The tools and reagents for this method are all available. However, HPLC or other analytical chemistry techniques make this a low throughput assay, depending on the level of automation. A primary advantage of this in vitro method is that it directly informs hypotheses regarding the specific mechanism by which a chemical may impact TH synthesis in vitro.  

In fish, increases of TPO mRNA levels are often used as indirect evidence of TPO inhibition in in vivoexperiments (Baumann et al., 2016; Nelson et al., 2016; Wang et al., 2020).

Domain of Applicability

A description of the scientific basis for the indicated domains of applicability and the WoE calls (if provided).  More help


This KE is plausibly applicable across vertebrates. TPO inhibition is a MIE conserved across taxa, with supporting data from experimental models and human clinical testing. This conservation is likely a function of the high degree of protein sequence similarity in the catalytic domain of mammalian peroxidases (Taurog, 1999). Ample data available for human, rat, and porcine TPO inhibition demonstrate qualitative concordance across these species (Schmultzer et al., 2007; Paul et al., 2013; Hornung et al., 2010). A comparison of rat TPO and pig TPO, bovine lactoperoxidase, and human TPO inhibition by genistein demonstrated good qualitative and quantitative (40–66%) inhibition across species, as indicated by quantification of monoiodotyrosine (MIT) and diiodotyrosine (DIT) production (Doerge and Chang, 2002). Ealey et al. (1984) demonstrated peroxidase activity in guinea pig thyroid tissue using 3,3'-diaminobenzidine tetrahydrochloride (DAB) as a substrate that is oxidized by the peroxidase to form a brown insoluble reaction product. Formation of this reaction product was inhibited by 3-amino-1,2,4-triazole and the TPO inhibitor, methimazole (MMI). A comparative analysis of this action of MMI between rat- and human-derived TPO indicates concordance of qualitative response. Data also suggest an increased quantitative sensitivity to MMI in rats compared to humans (Vickers et al., 2012). Paul et al. (2013) tested 12 chemicals using the guaiacol assay using both porcine and rat thyroid microsomes. The authors concluded that there was an excellent qualitative concordance between rat and porcine TPO inhibition, as all chemicals that inhibited TPO in porcine thyroid microsomes also inhibited TPO in rat thyroid microsomes when tested within the same concentration range. In addition, these authors noted a qualitative concordance that ranged from 1.5 to 50-fold differences estimated by relative potency. Similarly, Takayama et al. (1986) found a very large species difference in potency for sulfamonomethoxine between cynomologus monkeys and rats.

Life stage:

Applicability to certain life stages may depend on the species and their dependence on maternally transferred THs during the earliest phases of development. The earliest life stages of teleost fish rely on maternally transferred THs to regulate certain developmental processes until embryonic TH synthesis is active (Power et al., 2001). As a result, TPO inhibition is not expected to decrease TH synthesis during these earliest stages of development. Evidence supporting this hypothesis is obtained from a zebrafish TPO knockout line. In homozygous individuals TPO is inhibited from the embryonic developmental stage onwards, resulting in an abolished T4 production in thyroid follicles with phenotypical abnormalities such as reduced swim bladder inflation and growth retardation appearing at 20 dpf but not before 10 dpf (Fang et al., 2022). In zebrafish, Opitz et al. (2011) showed the formation of a first thyroid follicle at 55 hours post fertilization (hpf), Chang et al. (2012) showed a first significant TH increase at 120 hpf and Walter et al. (2019) showed clear TH production already at 72 hpf and not at 24 hpf but did not analyse time points between 24 and 72 hpf. In fathead minnows, a significant increase of whole body TH levels was already observed between 1 and 2 dpf, which corresponds to the appearance of the thyroid anlage at 35 hpf prior to the first observation of thyroid follicles at 58 hpf (Wabuke-Bunoti and Firling, 1983). It is still uncertain when exactly embryonic TH synthesis is activated and how this determines sensitivity to TPO inhibition.


This KE is plausibly applicable to both sexes. The molecular components responsible for TH synthesis, including TPO, are identical in both sexes. Therefore inhibition of TPO is not expected to be sex-specific.


List of the literature that was cited for this KE description. More help

Baumann L, Ros A, Rehberger K, Neuhauss SCF, Segner H. 2016. Thyroid disruption in zebrafish (danio rerio) larvae: Different molecular response patterns lead to impaired eye development and visual functions. Aquatic Toxicology. 172:44-55.

Brown RS, Shalhoub V, Coulter S, Alex S, Joris I, De Vito W, Lian J, Stein GS.  Developmental regulation of thyrotropin receptor gene expression in the fetal and neonatal rat thyroid: relation to thyroid morphology and to thyroid-specific gene expression.  Endocrinology. 2000 Jan;141(1):340-5.

Brucker-Davis F. 1998. Effects of environmental synthetic chemicals on thyroid function. Thyroid 8:827-856.

Campinho MA, Saraiva J, Florindo C, Power DM. 2014. Maternal thyroid hormones are essential for neural development in zebrafish. Molecular Endocrinology. 28(7):1136-1149.

Chang, H. C. and D. R. Doerge (2000) Dietary genistein inactivates rat thyroid peroxidase in vivo without an apparent hypothyroid effect. Toxicol Appl Pharmacol. 168:244-252.

Chang J, Wang M, Gui W, Zhao Y, Yu L, Zhu G. 2012. Changes in thyroid hormone levels during zebrafish development. Zoological Science. 29(3):181-184.

Crane HM, Pickford DB, Hutchinson TH, Brown JA. 2004. Developmental changes of thyroid hormones in the fathead minnow, pimephales promelas. General and Comparative Endocrinology. 139(1):55-60.

Divi, R. L., & Doerge, D. R. (1994). Mechanism-based inactivation of lactoperoxidase and thyroid peroxidase by resorcinol derivatives. Biochemistry 33(32), 9668–9674.

Divi, R. L., Chang, H. C., & Doerge, D. R. (1997). Anti-Thyroid Isoflavones from Soybean. Biochem. Pharmacol.  54(10), 1087–1096.

Doerge DR, Chang HC. Inactivation of thyroid peroxidase by soy isoflavones, in vitro and in vivo. J Chromatogr B Analy Technol Biomed Life Sci. 2002 Sep 25;777(1-2):269-79.

Dong, H.Y., Godlewska, M., Wade, M.G., 2020. A rapid assay of human thyroid peroxidase activity. Toxicology in Vitro 62

Ealey PA, Henderson B, Loveridge N.A quantitative study of peroxidase activity in unfixed tissue sections of the guinea-pig thyroid gland. Histochem J. 1984 Feb;16(2):111-22.

Fang, Y., Wan, J. P., Zhang, R. J., Sun, F., Yang, L., Zhao, S. X., Dong, M., & Song, H. D. (2022). Tpo knockout in zebrafish partially recapitulates clinical manifestations of congenital hypothyroidism and reveals the involvement of TH in proper development of glucose homeostasis. General and Comparative Endocrinology, 323–324.

Fukiishi Y, Harauchi T, Yoshizaki T, Hasegawa Y, Eguchi Y.  Ontogeny of thyroid peroxidase activity in perinatal rats. Acta Endocrinol (Copenh). 1982 101(3):397-402.

Holzer G, Morishita Y, Fini JB, Lorin T, Gillet B, Hughes S, Tohmé M, Deléage G, Demeneix B, Arvan P, Laudet V. Thyroglobulin Represents a Novel Molecular Architecture of Vertebrates. J Biol Chem. 2016 Jun 16.

Hornung, M. W., Degitz, S. J., Korte, L. M., Olson, J. M., Kosian, P. a, Linnum, A. L., & Tietge, J. E. (2010). Inhibition of thyroid hormone release from cultured amphibian thyroid glands by methimazole, 6-propylthiouracil, and perchlorate. Toxicol Sci 118(1), 42–51.

Hurley PM. 1998. Mode of carcinogenic action of pesticides inducing thyroid follicular cell tumors in rodents. Environ Health Perspect 106:437-445.

Kaczur, V., Vereb, G., Molnár, I., Krajczár, G., Kiss, E., Farid, N. R., & Balázs, C. (1997). Effect of anti-thyroid peroxidase (TPO) antibodies on TPO activity measured by chemiluminescence assay. Clin. Chem 43(8 Pt 1), 1392–6.

Kessler, J., Obinger, C., Eales, G., 2008. Factors influencing the study of peroxidase- generated iodine species and implications for thyroglobulin synthesis. Thyroid 18, 769–774.

Nelson K, Schroeder A, Ankley G, Blackwell B, Blanksma C, Degitz S, Flynn K, Jensen K, Johnson R, Kahl M et al. 2016. Impaired anterior swim bladder inflation following exposure to the thyroid peroxidase inhibitor 2-mercaptobenzothiazole part i: Fathead minnow. Aquatic Toxicology. 173:192-203.

OECD (2017) New Scoping Document on in vitro and ex vivo Assays for the Identification of Modulators of Thyroid Hormone Signalling. Series on Testing and Assessment. No. 207.  ISSN: 20777876 (online)

Opitz R, Maquet E, Zoenen M, Dadhich R, Costagliola S. 2011. Tsh receptor function is required for normal thyroid differentiation in zebrafish. Molecular Endocrinology. 25(9):1579-1599.

Paul KB, Hedge JM, Macherla C, Filer DL, Burgess E, Simmons SO, Crofton KM, Hornung MW. Cross-species analysis of thyroperoxidase inhibition by xenobiotics demonstrates conservation of response between pig and rat. Toxicology. 2013. 312:97-107

Paul, K.B., Hedge, J.M., Rotroff, D.M., Hornung, M.W., Crofton, K.M., Simmons, S.O. 2014. Development of a thyroperoxidase inhibition assay for high-throughput screening. Chem.  Res. Toxicol. 27(3), 387-399.

Paul-Friedman K, Watt ED, Hornung MW, Hedge JM, Judson RS, Crofton KM, Houck KA, Simmons SO. 2016. Tiered High-Throughput Screening Approach to Identify Thyroperoxidase Inhibitors Within the ToxCast Phase I and II Chemical Libraries.  Toxicol Sci. 151:160-80.

Pintar, J.E. (2000) Normal development of the hypothalamic-pituitary-thyroid axis. In. Werner & Ingbar’s The Thyroid. (8th ed), Braverman. L.E. and Utiger, R.D. (eds) Lippincott Williams and Wilkins, Philadelphia.

Power DM, Llewellyn L, Faustino M, Nowell MA, Bjornsson BT, Einarsdottir IE, Canario AV, Sweeney GE. 2001. Thyroid hormones in growth and development of fish. Comp Biochem Physiol C Toxicol Pharmacol. 130(4):447-459.

Remy L, Michel-Bechet M, Athouel-Haon AM, Magre S. Critical study of endogenous peroxidase activity: its role in the morphofunctional setting of the thyroid follicle in the rat fetus. Acta Histochem. 1980;67(2):159-72.

Ruf, J., & Carayon, P. (2006). Structural and functional aspects of thyroid peroxidase. Archives of Biochemistry and Biophysics, 445(2), 269–77.

Ruuskanen S, Hsu BY. 2018. Maternal thyroid hormones: An unexplored mechanism underlying maternal effects in an ecological framework. Physiological and Biochemical Zoology. 91(3):904-916.

Santisteban P, Bernal J. Thyroid development and effect on the nervous system. Rev Endocr Metab Disord. 2005 Aug;6(3):217-28.

Schmutzler, C., Bacinski, A., Gotthardt, I., Huhne, K., Ambrugger, P., Klammer, H., Schlecht, C., Hoang-Vu, C., Gruters, A., Wuttke, W., Jarry, H., Kohrle, J., 2007a. The ultraviolet filter benzophenone 2 interferes with the thyroid hormone axis in rats and is a potent in vitro inhibitor of human recombinant thyroid peroxidase. Endocrinology 148, 2835–2844.

Stinckens E, Vergauwen L, Blackwell BR, Anldey GT, Villeneuve DL, Knapen D. 2020. Effect of thyroperoxidase and deiodinase inhibition on anterior swim bladder inflation in the zebrafish. Environmental Science & Technology. 54(10):6213-6223.

Stinckens E, Vergauwen L, Schroeder A, Maho W, Blackwell B, Witters H, Blust R, Ankley G, Covaci A, Villeneuve D et al. 2016. Impaired anterior swim bladder inflation following exposure to the thyroid peroxidase inhibitor 2-mercaptobenzothiazole part ii: Zebrafish. Aquatic Toxicology. 173:204-217.

Taurog A. 2005. Hormone synthesis. In: Werner and Ingbar’s The Thyroid: A Fundamental and Clinical Text (Braverman LE, Utiger RD, eds). Philadelphia:Lippincott, Williams and Wilkins, 47–81

Taurog, a, Dorris, M. L., & Doerge, D. R. (1996). Mechanism of simultaneous iodination and coupling catalyzed by thyroid peroxidase. Archives of Biochemistry and Biophysics, Taurog A. Molecular evolution of thyroid peroxidase. Biochimie. 1999 May;81(5):557-62

Takayama S, Aihara K, Onodera T, Akimoto T. Antithyroid effects of propylthiouracil and sulfamonomethoxine in rats and monkeys. Toxicol Appl Pharmacol. 1986 Feb;82(2):191-9.

Thorne N, Auld DS, Inglese J.  Apparent activity in high-throughput screening: origins of compound-dependent assay interference. Curr Opin Chem Biol. 2010 Jun;14(3):315-24.

Thorpe-Beeston JG, Nicolaides KH, McGregor AM. Fetal thyroid function. Thyroid. 1992 Fall;2(3):207-17. Review.

Tietge JE, Degitz SJ, Haselman JT, Butterworth BC, Korte JJ, Kosian PA, Lindberg-Livingston AJ, Burgess EM, Blackshear PE, Hornung MW. 2013. Inhibition of the thyroid hormone pathway in xenopus laevis by 2-mercaptobenzothiazole. Aquatic Toxicology. 126:128-136.

Vergauwen L, Cavallin JE, Ankley GT, Bars C, Gabriels IJ, Michiels EDG, Fitzpatrick KR, Periz-Stanacev J, Randolph EC, Robinson SL et al. 2018. Gene transcription ontogeny of hypothalamic-pituitary-thyroid axis development in early-life stage fathead minnow and zebrafish. General and Comparative Endocrinology. 266:87-100.

Vickers AE, Heale J, Sinclair JR, Morris S, Rowe JM, Fisher RL. Thyroid organotypic rat and human cultures used to investigate drug effects on thyroid function, hormone synthesis and release pathways. Toxicol Appl Pharmacol. 2012 Apr 1;260(1):81-8.

Wabukebunoti MAN, Firling CE. 1983. The prehatching development of the thyroid-gland of the fathead minnow, pimephales-promelas (rafinesque). General and Comparative Endocrinology. 49(2):320-331.

Walpita CN, Van der Geyten S, Rurangwa E, Darras VM. 2007. The effect of 3,5,3'-triiodothyronine supplementation on zebrafish (danio rerio) embryonic development and expression of iodothyronine deiodinases and thyroid hormone receptors. Gen Comp Endocrinol. 152(2-3):206-214.

Walter KM, Miller GW, Chen XP, Yaghoobi B, Puschner B, Lein PJ. 2019. Effects of thyroid hormone disruption on the ontogenetic expression of thyroid hormone signaling genes in developing zebrafish (danio rerio). General and Comparative Endocrinology. 272:20-32.

Wang JX, Shi GH, Yao JZ, Sheng N, Cui RN, Su ZB, Guo Y, Dai JY. 2020. Perfluoropolyether carboxylic acids (novel alternatives to pfoa) impair zebrafish posterior swim bladder development via thyroid hormone disruption. Environment International. 134.

Zoeller, R. T., Tan, S. W., & Tyl, R. W. (2007). General background on the hypothalamic-pituitary-thyroid (HPT) axis. Critical Reviews in Toxicology, 37(1-2), 11–53.