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Thyroid UK
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Simple terms please

I have been on thyroxine for around 20 years. When I first had blood test due to chronic tiredness and rapid weight gain my results were borderline underactive. My GP said although my weight gain was due to this he could not prescribe medication. Eventually the results showed underactive thyroid and I built my way upto 150. Over the years I have never lost the weight and when complaining to the GP that thyroxine wasn't workin was told that some people do not realise what and how much they are eating lol ive made other attempts to get other medications but have always been brushed off. I can stick to a diet such as ww or slimming world to the latter and not lose an ounce! Lately I have been trying to understand a our t3 t4 etc but my fuzzy brain won't let me. Can anyone explain in a simple way please 💕

2 Replies

Gillandf, Levothyroxine isn't a weight loss aid but should rebalance your hormones so you don't gain uncontrolled weight and, if you are optimally medicated, you should be able to exercise and lose some weight on a calorie controlled diet. Ask your GP receptionist or practice manager for a copy of your recent results with the ranges (figures in brackets after results) and post them in a new question and members will advise whether you are optimally medicated.

TSH is a pituitary hormone. T4 and T3 are thyroid hormones. When the pituitary gland detects low circulating T4 and T3 it issues more TSH to prompt the thyroid gland to produce more T4 which will be converted to T3 in major organs. When sufficient T4 and T3 is detected the pituitary shuts down TSH. High TSH = low T4 and T3. Low TSH = high FT4 and FT3.

In the UK Free T4 (FT4) and Free T3 (FT3) are the usual thyroid hormone tests, the free meaning unbound to proteins and available for use in the cells.

Levothyroxine is also abbreviated to T4, and Liothyronine thyroid replacement is abbreviated to T3.


Many thanks. I will do what you suggest. I was once told by a GP after being called back after. Blood test that my thyroid was ok but my pituitary gland wS doing 'funny things'!! Wish I'd have had this help site then!


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