We always advised patients taking thyroxine to avoid anything with iodine in it like seaweed extract etc as this can affect your thyroid function and without frequent testing you could become over active!
Eating alot of brassica vegetables ( cabbage/broccoli etc) uncooked can reduce thyroid activity. Cooking removes most of the goitrogens so okay to eat it cooked although not every day.
T3 is available in tablet form but it is rather dangerous drug as it can have major adverse heart effects even with tiny overdose which is why its rarely prescribed in UK. It is rare for anyone to have very low levels of T3 on thryoxine which is why when someone does it makes the news. I have my T3 checked every few years although it can be difficult to get it done as some health authorities refuse to do it unless ordered by a consultant endocrinologist. You need to check with your GP.
I know of one lady who took T3 and she had her bloods checked every month and had to keep constantly altering her dosage of T3 to stay safe.
You may have come across amour thyroid extract as well, this is an extract from pigs and was what was used years ago before they synthesized thyroxine. Some people swear by it as it contains all the hormones your thyroid produces rather than the main ones in the synthetic drug BUT once again it can be dangerous as you have no idea of the dosage taken and need very frequent blood tests. It is available rarely on nhs for people who have an allergic reaction to thyroxine or they develop resistance to thyroxine both of which would be diagnosed by an endocrinogist not a GP. Plus there is the risk of animal disease being passed to humans. It is available over the internet but thats very dodgy to say the least!
One thing - its not often someone with diagnosed underactive thryoid, when taking thyroxine to be totally symptom free. The tablets replace all the really important hormones that your thyroid produces but not all of them so its normal for people to complain they find it hard to lose weight or their skin is dry etc even on treatment. Elevated cholesterol is another frequent effect as well.
If someone has elevated cholesterol then GP's will always check their thryoid levels as they could by hypothyroid.
Hope I haven't bored you with info
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