Confusing lab results?

I've been suspecting hypothyroidism for a while now, as I seem to have symptoms relating to it, such as difficulty in losing weight, unexplained high cholesterol, absent periods, difficulty concentrating and remembering things, dry hands and flaking nails. I had myself tested last year but the doctor said I was fine as the results were within range. However, I got them tested again and here are the results:

July 2014:

TSH 1.61 range 0.4-4.0

F T4 10.48 range 10-21

March 2015:

TSH 1.34 range 0.4-4.0

F T4 9.64 range 10-21

This is somewhat confusing as my Free T4 is below range, although my TSH is completely normal. I've been researching and this and think that this may be an indication of central hypothyroidism? Should I try to ask for medication or more lab tests?

6 Replies

  • The Free T3 test is best as it tells us how much of the Active hormone we have. You don't have much T4 or Free T4 - it is below range.

    These are a couple of links and you will get more responses from other members who've been in the same boat as yourself.

  • Ok, thank you very much for your reply!

  • Saratomu, you're right low-normal TSH with below range FT4 indicates secondary/central hypothyroidism. Low FT4 usually means FT3 is low and it is this which causes hypothyroid symptoms.

    Secondary hypothyroidism is usually due to pitutary dysfunction meaning insufficent stimulus is given to the thyroid gland to produce thyroid hormone. Hormone replacement (Levothyroxine) is necessary to replace lacking hormone although the thyroid gland itself is usually healthy. Your GP should also do some pituitary function tests to check other hormone levels and will probably refer you to an endocrinologist.

  • I'm getting a call from a doctor in a couple of days so I'll definitely press to get further tests done.

    Thank you so much for your help :)

  • If you look at the Clinical Knowledge Summaries published by NICE, it mentions secondary hypothyroidism several times - you will have to click on the tabs in the left hand column to find all the references (these are just the first two I came to) :

    This gives you some idea of what you should expect from your doctor.

  • Thank you for these!

    I've been reading up a lot about this now and am feeling a lot better about it.

    Thanks for replying :)

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