Hypothyroidism and TSH?

Question

Theoretically, if you give someone with hypothyroidism large doses of TSH instead of Thyroxine treatment, would it increase the Thyroxine in the individual to a normal level?

I know, there is a problem with the thyroid gland itself which is impering the Thyroxine production. But when you think about it, the Thyroxine level in a person with hypothyroidism is not zero, there is SOME, so this means the thyroid gland IS responding to TSH to a limited extent. So........ to me it makes sense that by making the TSH much higher than it already is the Thyroxine will increase as well. Is this not correct?

I am just curious about this, not planning anything.

Thanks to whoever responds!

Answer 1

No, it's not correct, as noted in the more detailed answer above.  The fact that the thyroid is making *some* T4 does not mean that it's capable of making *enough* T4.

Its inability to do so leads to increased TSH, and the only further response to elevated TSH is a pathological increase in cell proliferation.

Answer 2

It would depend on the cause. In primary hypothyroidism, TSH is elevated and serum free T4 is decreased so giving more TSH will not solve the problem because the thyroid itself can be unable to respond to TSH in certain conditions. In central hypothyroidism, TSH can be low, normal or slightly elevated and free T4 is decreased. Here there is an impaired TSH response to TRH (thyrotropin releasing hormone) which is released by the hypothalamus and signals the pituitary to release TSH. If the problem is the thalamus you would want to treat that instead of just giving the patient TSH, especially if they have a normal pituitary gland. So the answer to your question would be yes, only if the problem was that the pituitary could not respond to TRH or release TSH and the patient had normal hypothalamic and thyroid function.