arrested development since the last time rar

The review makes some recommendations about appropriate test method development needs.

In view of this information, it may be possible to develop an invertebrate‐based screen that is sensitive to vertebrate THADCs which interfere with thyroid hormone synthesis or metabolism along with interaction with membrane receptors. Instead, the unliganded nuclear receptor itself controls metamorphosis in molluscs, echinoderms and tunicates, while the T3 derivative tri‐iodothyroacetic acid (TRIAC) acts as a THR ligand in cephalochordates. Thyroid hormone regulates inter alia metamorphosis, but unlike in vertebrates, this does not occur via receptor activation by the ligands triiodothyronine (T3) and thyroxine (T4).

Thyroid hormone may act in these phyla through interaction with a membrane integrin receptor. These phyla are able to synthesise thyroid hormone which has been shown in some groups to induce the nuclear thyroid hormone receptor (THR). Although arthropods including crustaceans do not contain a functional thyroid signalling system, elements of such a system exist in the aquatic phyla molluscs, echinoderms, tunicates and cephalochordates. Such a screen might assist the phasing‐out of some vertebrate testing. This review examines the presence and evolution of thyroid‐like systems in selected aquatic invertebrates with a view to the potential use of these organisms in screens for vertebrate thyroid hormone axis disrupting chemicals (THADCs).

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