I would say, because you have Hashi's. And, in Oct 2017, you had a Hashi's 'hyper' swing - aka Hashi's flare - where the dying cells of your thyroid dumped their store of thyroid hormone into the blood, causing levels of T4 and T3 to temporarily soar. Now, all that extra hormone has been used up/excreted, and you are hypo again.
Also symptoms of cold intolerance, dry eyes, dry skin, hair loss, puffy eyes, goitre, difficult swallowing, hard stool, heavy periods, pins and needles, joint pain, pale skin, bruising, depression, memory loss
This is a list of symptoms and I think you can add a few more to your list. I also believe you need your dose increased from 50mcg to 75mcg and another test in six weeks.
50mcg is also a very low dose of hormone. The December results represent your everyday levels of hormone, an it's clear you're extremely undermedicated. You must feel dreadful, sometimes it's even worse to be on a very low dose.
Going gluten free often helps to reduce antibodies, that is a very serious flare up you had, so reducing the antibodies would help you a lot.
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