Re: Levoxyl, then Levothyroxine, then Synthroid, now what?
Levothroid's inert ingredients include microcrystalline cellulose, calcium phosphate dibasic, povidone and magnesium stearate. Tirosint is a newer product that contains only gelatin, glycerin and water as inerts.
You might be able to have a compounding pharmacy make up encapsulated T4 without offending binders, fillers, or dyes.
You could also try a natural desiccated thyroid replacement. Their inert ingredients vary, but that information is readily available on the net or from any registered pharmacist.