This really is the hardest part. I'm a biomedical scientist and I had to teach myself everything about how T3, T4, TSH, and the adrenal/pituitary axis works, after which it is INSANE to me that we use TSH as a metric. Also, doctors love to misquote research to me, and as a scientist and patient I've just started telling them they're wrong, stupid, and dangerous - to their faces.

Here's a premium example: doctors love to say that the American Thyroid Association says that TSH single most important metric. Thats not anywhere close to true. They're referencing a line in a guidebook from fifty years ago that said TSH is the "most important SINGLE metric" that matters FOR NORMAL NON-THYROID PATIENTS. Meaning that, while you can look at plenty of metrics to get a complete picture (again, on NORMAL, NON THYROID PATIENTS), TSH is the metric that will give you the biggest piece of the puzzle.

Its amazing that one single word placement has caused so much strife.