Does supplementing Thyroid T3 or T4 reduce endogenous production?

[Uptime]

Hi All,

I’m interested to know whether supplementing T4 and/or T3 has any impact on the endogenous production / conversion by the Thyroid gland?

e.g Does the Thyroid continue to ‘do it’s best’ in response to TSH signals .. or does it become even less efficient ‘lazy’ at releasing T4/T3 as it is being supplemented exogenously?

thanks

Ross

[tattybogle]

The only driver for the thyroid to make more than dribble of T4/T3 is the TSH (thyroid stimulating hormone) .. when you add exogenous T4 or T3, the TSH inevitably lowers in response .. so the thyroid is inevitably turned down to 'very low'.. because with a lower TSH it's being 'asked' to do less.

'How much' the thyroid still 'tries' depends entirely on how low the TSH goes in response to the dose taken . but at TSH 0.5 it won't be trying as hard as it would if TSH was over 2. and if TSH is much lower than 0.5 it probably won't be trying very much at all.

[greygoose]

I don't think you should think of levo and liothyronine as 'supplements'. They are Thyroid Hormone Replacements.

[Catseyes235]

I’m afraid my experience probably isn't relevant as I had Radio Active iodine so essentially have no thyroid left.