That was a good read. Its still unclear to me how the thyroid gland determines when to convert t4 to t3. I understand that the pituitary gland senses low levels of t3 an t4, so it releases TSH, which then signals the thyoird gland to produce thyroid hormones, mostly t4 but some t3, but it doesnt give any explanation on how it knows when to convert the t4 to t3. But I guess what i was saying was true about taking supplemental thyroid hormones will shut down the bodies naturally production. The body will sense it has high enough levels of t4 and t3 since your taking a synthetic form, and though the negative feedback loop it will shutdown the pituitary glands production of tsh which means the thyroid will not be signaled to produce t4 and t3. but this doenst matter since your supplementaing. Its basically exacty the same as when we take synthetic steroid hormones, the hypothalamus senses exogenous hormones, so it stops producing gnrh, which means the pituitary will not produce LH and FSH, so the testes will not produce testosterone. Same kinda thing when using exogenous thyroid hormones. But from the reading I've done on them the risk of permanent is extremely low and once you stop taking them you usually bounce back within 2 weeks, even after it being shut down for a very very long time. Definitely an interesting subject to learn about tho.

One thing I did learn from that article is synthetic t3, or even natural t3 has a very short half life, and even if you were to split your doses you would still have some extremely high peak levels of t3 which is harmful to the body. So t4 is much more appropriate in this situation.