I've done a lot of work with Vit D3.
Quite against all standard medical advice from my GP and my infuriated endo, I took c.80,000IU a day for about 6 weeks, then I got tested. It came back at 90 nmol/L, and I wanted, based on my research, to be in the 100-200 bracket for optimal immune function and bone health (I had advancing osteoporosis due to oestrogen breast cancer, chemo, anti oestrogen drugs, etc).
Knowing that the whole scare tactic over Vit D toxicity was in fact, high blood calcium (hypercalcaemia) caused by a) D3 increasing calcium pick up from the gut, and b) a lack of Vit K2, which picks up any excess blood calcium and sends it straight to the bones and teeth, I took 1mg K2 combined MK4 and MK7. The MK4 form is faster acting and is used in Japan to treat osteoporosis, which in the UK, is deemed medically impossible to achieve. MK7 lasts longer in the body, but is slower acting.
When, at 3 months and 6 months after starting my D3 and K2 regimen, my two DEXA scans came back showing a reversal of the osteoporosis, my GP was enthralled, but my endo practically exploded with fury. We had the most monumental row over it, because he insists, despite the evidence of his own eyes, that K2 "does nothing!" Well, clearly it does.
Even more annoyingly for my endo, and to the amusement of my GP, every single month they tested everything, D3, calcium, liver and kidney function, immune system, RBC, different minerals, the works, and every single month everything came back normal. They did that for two whole years before my endo was forced to admit that I wasn't killing myself, which he'd promised more than once would happen of I persisted in my madness
Unfortunately, I did eventually succumb to the pressure he brought to bear, and reduced my D3 from my maintenance dose of 10-20,000IU/d, with 150,000IU/d for three days only, if I got an eye infection or something, and consequently got really ill again. Gee, thanks, doc.
I've just recently started upping it again from 10,000IU/d to 50.
They keep lowering the "sufficient" ref range figure. When I started looking at D in 2013, the Sufficiecy figure was c.90, but 100-200nmol/L was considered optimal. I understand the sufficiency figure is now somewhere around 50 or 60, which simply isn't enough, IMHO. They keep lowering the Insufficiency and Deficiency figures, too. I think it used to be 20 to count as deficient, now it's 10, I think. I know I made my Dad get tested, and he tested at 15, which was enough to count as deficient then, and now isn't.
When you're ill, your body uses up D3 at a vast rate of knots. When you have insufficient D3, you have more muscle pain, more joint pain and stiffness, more depression, more infections, more everything crappy and less immune function.
Also, the D3 test shows the levels of 25 OH D3, whch is inactive and has to be converted to calcitriol before your cells can use it. If you're iodine deficient, proper conversion isn't possible, so you can test high for 25OH D3, but actually still be deficient at a cellular level if you haven't got enough iodine to do the job.
Given that you're hypo t, with no antibodies, it's a safe bet that you are iodine deficient. All of us with hypo t (and hypo adrenals) are.