Thyroid UK
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Anyone else find they lose weight when their free t's are low in range???

I just found my old labs from February 2014.


I was taking 75 t4 and 15 t3...

Results showed Both very low in range..BUT MY WEIGHT WAS WHERE I LIKED IT...

Now my free t's are approximately 70% of range and my weight keeps climbing, despite eating/exercising the same!

Why is this?????

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I should have also mentioned that i am now taking 100 t4 and 12.5 t3....reason is because i keep reading that most people feel great when their free's are in top half of range!

..but why the weight gain??????



From the numbers you just posted, it looks like you're taking more t4 than before, but slightly less t3. That could be part of the reason why your weight is fluctuating. I've been told mid range for t4 and upper range for t3 is optimal for a lot of people. Also, if t4 isn't properly converting to t3 that could be a contributing factor, or issues with your adrenal glands, too much/little cortisol... has been a helpful resource for me as we'll as

Maybe you will find them useful as we'll.


Thank you.

I should say that i have tried various combinations of t4 and t3...and t4 only as well...i have had the mid-range t4 and top range of t3 but felt absolutely horrible.

I felt ok on 75 t4 and 15 t3 but the endo i had at the time was absolutely against me continuing on ANY t3 as it could cause heart issues i quit seeing her...when i went to another endo he said he'd like to see my free t's a bit higher and that's how all the maddness started!

I am in the process of changing endos once again.


But i find it quite strange that my weight went down and stayed down on such a small dose of meds!!!!!


Have you considered trying natural desiccated thyroid? Also, keep in mind we are all unique and what works for some may not work for others. The thing that matters is you finding a medication, dose, and free t levels that work best for your body, as well as a doctor who's supportive and willing to work with you.

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Thank you.😊

Yessssss i am finally coming to realize how different i am from the majority hahaaa...just curious if anyone else here has had a similar result as me and my i find it quite peculiar


One reason for loss of weight when thyroid hormone levels are low is loss of muscle mass. Keep a careful eye on that. (Not at all sure how to do that! But if you lose strength and when you pinch obvious big muscles, they seem to be smaller, would look like indicators - but perhaps a bit too subjectove and rather blunt.)

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I definitely think i gain in water weight to be honest.

My belly is a big bowl of jelly when my free t's get up in range



Sometimes, if your thyroid hormones are low, your adrenals pump out adrenaline to keep you going. For some, that means anxiety and palpitations; for others weight loss. But honestly, I don't know.


I feel less anxious when levels drop.

I think thyroid meds causes me to be crazy when higher in range😢😢😢



I lost all excess weight, have managed to maintain, and function best on LOW thyroid hormones in range, and wouldn't dare take them higher after a previous unwanted reaction.

T3 is the active hormone that if allowed to work correctly will stimulate almost every aspect of carbohydrate metabolism and after initially medicating T3 I felt extra hungry until hormones rebalanced.

T3 increases the absorption of glucose by the intestinal tract, the uptake of glucose by the cells, and glycolysis. It causes the fat cells to release free fatty acids into the bloodstream where they are taken up by the tissues and burned by the hyperactive mitochondria to make the ATP that drives our muscle contractions and makes exercise possible. (In glycolysis, the excess glucose that is not needed for glycogen production, is broken down and burned by the mitochondria to produce even more ATP).

I read the longer we medicate T3, the more it increases the mitochondria's ability to burn calories, raising the basal metabolic rate (BMR) until we reach our optimum.. In addition, T3 will also increase the number and size of mitochondria, which will further serve to increase BMR.

T3 influences other hormones and can cause blood sugar levels to rise, meaning the pancreas will release more insulin in response. Therefore, it is important to eat 3 healthy meals a day, including protein and fats in each which keeps us feeling full for longer and blood sugar levels more stable.

It is true that exercising will initially use thyroid hormones up but long term is productive as thyroid hormones eventually perform better within muscle than fat, by increasing all aspects of protein synthesis. This increases muscle further and so the efficiency that fat is burned.

Thyroid hormone levels are so multifactorial and extremely individual. More is not always better and can be actually counter productive. If you are still losing weight, it sounds as if you have excessive thyroid hormone driving your metabolism. If you are still exhibiting hypothyroid symptoms, it may be your dose requires tweaking and you have other nutrient//iron deficiencies that need addressing.


Thank you!

Would you mind posting your free t4 and free t3 results please?

Including their respective ranges?



Any exercise uses up precious T3.


So one should not exercise???




Without a thyroid you should consider seriously taking NDT. A partially working thyroid produces at least some of the other products of a healthy thyroid, without a thyroid you get none. Those other products are produced by the thyroid for a very good reason - you need them, if you didn't need them then it wouldn't produce them. Why it is believed that pure synthetic levothyroxine and liothyronine can fully substitute for natural thyroid hormone is quite astonishing.

It's like saying that pure alcohol mixed with water will make a very good whisky.


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