RIA and ELISA are both immunoassays, i.e. they are antibody-based. Performance and cross-reactivities depend on the antibody employed. I have used ELISA and TR-FIA (time-resolved fluorescence immunoassay) to detect free and total TH levels in fish plasma.

Wouldn't say that RIA is more cost-effective than ELISA. For the latter a multiplate reader or spectrophotometer will suffice, for the former you'll require beta- or gamma counters which are much more expensive.

Perhaps most important, irrespective of the assay principle: most commercial kits are for use in human plasma. Take care to validate your assays thoroughly before applying them in your experiments involving animals.

You can validate a kit for your plasma samples by constructing serial dilutions of plasma with stripped charcoal-treated plasma. Curves should run parallel to the standards supplied, indicating a similar interaction of the antibody with its epitope (TH) in the matrix of your sample. Likewise, you can spike stripped plasma with known amounts of TH to assess the behaviour of the assay.

RIA is the best!!! You can moove sensibility for the range on T3 or T4 , using always homologous serum for the standards. We developed severel years ago this RIA for human, cows, rats, fish and chiken. We developed our antibody in rabbit, preparing a conjugated and moove the standars into the right range of each specie. Diluting the antibody or the 125-T3 or T4. Separating method charcoal-Dextran. If you want more information, take a look to my contributions. I'll be glad to help you. Also, now I remember some comercial RIA kits are specific for rats.

Also keep in mind what you wish to measure: total or free thyroid hormone concentrations.

And: if it is your goal to assess hyper- or hypothyroidism, then TSH expression or plasma levels is more appropriate.

I am also going to do some thyroid hormone test in transgenic mouse model. Any recommendation for reliable commercial ELISA kit?

Can anyone provide me a protocol of ELISA technique for determining T3 or T4 leve?

hi Justin

as you know thyroxine and triiodothyronine is a kind of Amine hormones which through action of enzymes in the cytoplasmic part of the glandular cells are made up and then absorb the vesicles can be made ahead up to the time of discharge, they will remain.

so, i think it is better to use ELISA kit because at the bottom of the plate antibody is coated and can detect THs levels in plasma.

i used the Kit named (monobind, Lake Forrest, California) which was really good and effective.

ELISA is the best and safe technique for T3 and T4 determination.