I remember I diluted Tyronene in MCT oil and applied only 1mcg on my wrist as a safety. It was my first time taking thyroid.I used it topically in the past for up to 6 months, with zero effect on lab work.
It has been stated elsewhere on the forum that thyroid does not absorb systemically via topical application. In fact I recall previously reading that thyroid is deactivated within the skin.
Sublingual, and oral application are likely best. Naval application might work, but again, going through portions of skin.
These products are designed in a manner so as the "topical application/lab use" verbiage allows for them to be purchased and sold with minimal to no restriction for the general public like ourselves.
How you apply the product is entirely up to you.
I certainly did feel a "pick up". I can still remember. So yes, it does work topically. Not the same way as orally or sublingually, but it does work.