Table 3.

The Top 25 Ranked ToxCast Chemicals for Inhibition of Iodotyrosine Deiodinase (IYD), Based on Absolute IC₅₀.

				Single-Conc.	Concentration-Response
Rank	Chemical	CASRN	Max Tested Conc., μM	Median % Inhibition a	% Inhibition at Max Conc. b	IC20 (μM)	IC50 (μM)
-	3-Nitro-L-tyrosine c	621-44-3	200	NA d	100	0.01	0.04
1	Methylene blue	61-73-4	200	54	53	1.9	3.4
2	Tannic acid	1401-55-4	70	92	101	6.6	7.8
3	Diquat dibromide monohydrate	6385-62-2	100	90	98	5.8	11.7
4	D&C Red 27	13473-26-2	132	78	78	4.1	13.4
5	Dodecylphenol	27193-86-8	200	97	100	11.6	20.1
6	Lauryl gallate	1166-52-5	200	87	107	11.9	22.3
7	4-Dodecylphenol	104-43-8	200	90	99	6.9	23.1
8	4-Nonylphenol	104-40-5	200	80	98	8.9	23.6
9	Dinocap	39300-45-3	200	88	98	19.8	23.8
10	Hexadecyltrimethylammonium bromide	57-09-0	200	97	104	20.7	24.7
11	Sodium myristyl sulfate	1191-50-0	200	82	104	11.3	25.7
12	Calcium dodecylbenzene sulfonate	26264-06-2	200	102	105	17.1	26.0
13	Methyltrioctylammonium chloride	5137-55-3	200	96	101	7.7	26.1
14	Triclosan	3380-34-5	200	79	112	10.4	28.7
15	2,2’-Methylenebis(4methyl-6-tertbutylphenol)	119-47-1	200	72	92	7.7	28.9
16	Sodium hexyldecyl sulfate	1120-01-0	100	58	102	14.5	29.5
17	Sodium tridecyl sulfate	3026-63-9	200	95	107	16.1	31.7
18	Sodium dodecylbenzenesulfonate	25155-30-0	200	90	107	17.8	32.1
19	Methylbenzethonium chloride	25155-18-4	1000	103	105	13.6	32.2
20	Docusate sodium	577-11-7	200	94	100	16.2	33.0
21	Kepone	143-50-0	200	56	95	7.6	33.4
22	Oleic acid	112-80-1	200	87	89	21.3	34.1
23	Dodecylbenzenesulfonic acid	27176-87-0	200	88	102	20.1	34.5
24	Octylparaben	1219-38-1	200	82	107	16.8	35.2
25	C.I. Acid Red 114	6459-94-5	140	99	103	18.0	36.9

^aMedian of three replicates in single concentration screening (at maximum concentration)

^bMedian of three replicates at maximum concentration of chemical in concentration-response screening; in three chemicals (Methylene blue, Tannic Acid, and D&C Red 27) concentrations below the maximum tested concentration produced greater inhibition (see Fig. 3).

^cMNT, known IYD inhibitor included as positive control in concentrationresponse on every assay plate, with 41 plates each tested in triplicate. Mean IC₂₀ and IC₅₀ values across all plate reported in table. IC₅₀ values ranged from 0.012 to 0.076 μM with mean = 0.035 μM and SD = 0.016.

^dNA, not applicable