Thyroid UK

Comparison results

My thyroid test last April was -

TSH - 1.7, range is 0.10-4.00

T4 - 9.6, range is 10-22

Last week it was

TSH - 2.00

T4 - 9.8

Does this mean things are improving? I have been referred to an endo and need repeat bloods every 3m.

My doctor is no use in explaining the difference in the two tests so I was wondering if someone here could explain it to me?


1 Reply

Jessica, Thyroid Stimulating Hormone is produced by the pituitary gland to stimulate the thyroid gland to produce thyroxine (T4) when it detects low circulating T3 hormone.

T4 is a pro-hormone which is converted to T3, the active hormone, in the thyroid gland and major organs.

Your TSH is low-normal but your FT4 is below range on both tests which means you are unlikely to be producing sufficient T3 and this is why you have hypothyroid symptoms.

You should ask your GP to consider secondary hypothyroidism (hypopituitarism) which is often caused by pituitary dysfunction. Your thyroid gland is probably healthy but isn't receiving sufficient stimulus to produce the required hormone. Treatment is Levothyroxine to replace the low thyroid hormone. TSH is not a reliable test in secondary hypothyroidism and FT4 and FT3 tests are the ones to rely on.

A pituitary function test should be done to check growth and sex hormone levels. When secondary hypothyroidism and pituitary dysfunction are suspected/confirmed patients are usually referred to an endocrinologist for investigation and management.

It may be helpful to show your GP these links:


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