This document is dominated by the beliefs of a certain Dr S Soldin. He believes quite rightly that some assays for FT4 and FT3 are below standard. I have always argued this. BUT some assays that he does not mention are up to standard. Furthermore whilst accusing others about the mote in their eyes he signally fails to admit the beam in his own. He advocates a technique called mass spectrometry + ultrafiltration as the gold standard method for measuring FT4 and FT3. This is a scientist who first did his experiments at the wrong temperature (a key factor in measuring FT4 and FT3), made a lot of allegations about the shortcomings of methods that did use the right temperature, was told about his error, corrected it but made no public admission and did not withdraw and has not withdrawn his previous erroneous work. Added to this are fundamental questions about one part of his method that I have raised and as far as I know he has not answered by my suggested experiments. The interesting extra problem is that FT3 would be more susceptible to the potential errors than FT4 though both could be affected. He does not mention that another gold standard method (equilibrium dialysis) does not really agree with his and correlates better with the assays now done. Solid again raises the old chestnut that immunoassays are affected by the serum T4(T3) binding protein levels e.g. in pregnancy. This might be true in some, but is definitely and provably untrue of ALL such assays. Also he mentions that immunoassays are affected by heparin, furosemide, salicylate and anti epileptic drugs. BUT his preferred method would be equally if not more so affected by the same drugs - not mentioned of course. The need for slow release T3 tablets is at last recognised. But it should be simple to regulate their use so that FT3 does not reach dangerous levels for AF and osteoporosis. This document is really a propaganda exercise by Soldin, which the US gurus have swallowed hook line and sinker, without a proper exhaustive analysis of the validity of what he himself is advocating. I know of one problem which I'll briefly describe. Part of his method involves filtering undiluted serum through a filter that lets out FT4 and FT3 only. BUT it lets out a lot of other small molecules e.g. sodium, chloride, phosphate to name a few. These are all electrically charged some + some -. So are the proteins left behind non filtered. Filtering out some fluid concentrates what's left behind. The ratio of electric charged molecules is thus altered comparing each side of the membrane and the nonflltered side becomes more concentrated in protein concentration. Thus there could an effect which by charge equalling will artificially filter more (or less) small molecules than the actual concentration originally in the serum. If this applies to FT4 and FT3 then Solid's work is negated. But he won't do the experiments to test for this well known phenomenon called the Donnan effect. I could go on moe, but it seems to be that he has "snowed" the US with seemingly impeccable work that potentially isn't.