Alicia,
That Saravan chap is interesting! I had come across quite a bit of Portuguese work (Escobar, Morreale, et al - from memory).
the pekingnese,
In the UK the official view is that we only have one proper brand of levothyroxine - Eltroxin. All the other versions are the generics.
Without a shadow of a doubt they are NOT identical to reach other. They vary in several ways:
Ingredients (other than levothyroxine)
How well they dissolve/disintegrate
How well you absorb them
What unwanted products are produced as the levothyroxine degrades.
A while ago I found some categoric research (from the US) which identified certain reactions that could occur - and the resultant degradation products. That suggested that certain formulations were inherently better than others.
Be warned - sometimes different strengths of tablet within one 'manufacturer's' product are actually made by different companies and to different formulations. (I think Teva 25mcg are different to Teva 50 & 100mcg.)
In addition to all that, the tablets can be between 90 and 110% of stated dosage. (Soon to be tightened up to 95-105%.) This is supposed to mean that they are within this range between manufacture and 'use by' date - provided they are stored carefully. But it is still quite significant.
My partner has tried Cytomel (US version of T3), Armour (desiccated porcine thyroid extract) and Levoxyl (US levothyroxine with an unusual formulation), and now Evotrox (UK levothyroxine suspension). She still isn't well - but some or all of these might have helped.
Specifically, she seems to be affected by minute dose changes and seems unable to take the same dose for more than a few days.
Both of you might be interested in this:
www.ncbi.nlm.nih.gov/pubmed/8641203
- but please also look up other papers by the same authors.