“High cholesterol after thyroidectomy and unusual test levels.”

I had my thyroid removed 21 years ago. My levels have never been in the normal range until the last 6 years, and even then it ran 3.7-3.9. I do have a small piece that "regrew" but it doesn't pass the function test which I have done every 5 years or so.
My last two blood tests came back as .43 and also high cholesterol. I know that .43 is still within normal range but it is not for me. My doctor did drop my intake to 6 days a week so that could also account for the lower numbers too I suppose.
My question is: Is it possible this dip in numbers could be related to my cholesterol? I have a farm and eat what we grow. No processed foods. Lots of fish and very little red meat. I'm struggling with how it could be diet related.