Bendaisy2 The aim of a treated hypo patient generally is for TSH to be 1 or below or wherever it is needed for FT4 and FT3 to be in the upper part of their respective reference ranges. When your TSH was 1.6 there was no need to reduce your dose from 50mcg daily. In fact an increase would have been in order.
Do they only test TSH, not FT4 as well? Ideally we should have TSH, FT4 and FT3 to give a full picture but doctors unfortunately seem to be TSH obsessed and most dose by that result alone, keeping many of us very unwell.
As your TSH jumped from 1.6 to 35 when lowering your Levo from 50mcg daily to 37.5mcg average daily, that is a tremendous difference and I wouldn't mind betting that you could have autoimmune thyroid disease aka Hashimoto's, where antibodies attack the thyroid and gradually destroy it. As and when the antibodies fluctuate, so do symptoms and test results. Ask for antibodies to be tested. NHS generally only do Thyroid Peroxidase antibodies but there are also Thyroglobulin antibodies, and you can be negative for TPO but positive for TG antibodies.
As well as Vit D, it would be useful to have B12, Folate and Ferritin tested. All our vitamins and minerals need to be at optimal levels, not just within range, for thyroid hormone to work properly. If not already done , ask for those additional tests.
As for your medication level, you need an increase. Please email firstname.lastname@example.org for a copy of the Pulse Online Magazine article by Dr Toft, leading endocrinologist and past president of the British Thyroid Association, which states:
"The appropriate dose of levothyroxine is that which restores euthyroidism and serum TSH to the lower part of the reference range - 0.2-0.5mU/l.
In this case, free thyroxine is likely to be in the upper part of its reference range or even slightly elevated – 18-22pmol/l. Most patients will feel well in that circumstance.
But some need a higher dose of levothyroxine to suppress serum TSH and then the serum-free T4 concentration will be elevated at around 24-28pmol/l.
This 'exogenous subclinical hyperthyroidism' is not dangerous as long as serum T3 is unequivocally normal – that is, serum total around T3 1.7nmol/l (reference range 1.0-2.2nmol/l)."
Print the article and highlight question 6 to show to your GP.