"Dr Toft states in Pulse Magazine, "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)."
You can email louise.roberts@thyroiduk.org for a copy, it is question 6, for your friend to show her GP.
Dr Toft is past president of the British Thyroid Association and leading endocrinologist. He also wrote a booklet "Understanding Thyroid Disorders", published by the British Medical Association for patients, in which he says many people do not feel well unless their levels are at the bottom of the TSH range or below and at the top of the FT4 range or a little above. Booklet available from pharmacies and Amazon for £4.95.
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