Best cortisol saliva test is one that measures cortisol plus DHEA, (don't do cortisol only), choice of Regenerus or Genova Diagnostics for that test. Regenerus sends results direct to you, Genova send them to ThyroidUK (who act as your "practioner" to enable you to order the test) and then ThyroidUK sends them on to you once they have your consent.
Vit D is fat soluble so any excess is stored and can lead to toxicity. It's very important to take the dose you need so you need test first, then there are important cofactors needed when taking D3 - magnesium and Vit K2-MK7. Seems as though your thyroid specialist GP knows as much about supplements as a normal GP! Come back with result for suggestion of appropriate dose and further information about the cofactors.
Selenium is generally said to be OK to supplement at 100mcg daily.
Zinc should be tested. Zinc and copper should be balanced, so ideally both should be tested. We Hypos tend to have one high and the other low, so you need to know where your levels are to know what to supplement.
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