Yes, the full panel needs to be sent to an outside lab, like Michigan State University or Idexx. It will test T3, Free T3, T4, Free T4, TSH, as well as something else I've forgotten. The full panel gives a clearer picture of what's going on.
Let me correct terminology a little here. Thyroid that will usual show values that you get on either a "full" blood panel or on a "senior"blood panel is actually just called a T4. Rosemary lists the correct information on a complete thyroid panel above: T3, Free T3, T4, Free T4 (Free T4 usually if you are reading the full report says something like Full T4--by equalibrium dialysis), TSH and TgAA (TSH and TgAA the two parts of the panel that are usually the indicators for a genetic thyroid problem but it takes all 5 parts to really see what's going on.
About Idexx and full Thyroid panels--our clinic uses Idexx (who also supplies our in house testing equipment) for a lot of our in house tests but if something is showing up in abnormal ranges there is rarely anything that the in house equipment can test for. We send secondary (more sensitive or different secondary tests_ all over the country.
There are very few places that do full Thyroid panels--TgAA is the one that most places can't do. MSU (Michigan State University still is the gold standard for Thyroid tests--including the 5 part complete panel. So when one of our vets who was dealing with a full panel got to talking to Idexx about it they told her that they could now do full panels. And I had one done on one of my dogs and we sent it to Idexx instead of MSU--it came back and all was fine until the next dog I wanted a full panel on--we sent it to Idexx and when the preliminary results came in TgAA was not included but a footnote was and it said that the sample had been sent to MSU for the TgAA--and when the final panel report was in sure enough there was another footnote that TgAA results were as reported by MSU.
You can go to MSU/thyroid panels and in the information section there is actually a list of labs who can do full panels. Idexx, which used to be listed is no longer listed. I'm doing this from memory--the only other lab I can think of offhand that really does their own complete thyroid panels is the one at Texas A & M's vet school.
T4 as on a routine blood panel or a senior blood panel is useful because it's sometimes the first indicator (other than the dogs own symptoms) of a thyroid problem. But some dogs never show low T4 values or they show low values but still within the reference range for whatever lab is doing the testing--and a lot of Dobes should be medicated if within a low normal range.
Thyroid is so common in Dobermans it probably should be checked for sooner rather than later but it doesn't often happen and I know a vet who I highly respect except for his view on Thyroid. His contention is that the most over medicated problem is dogdom is thyroid--most dogs do not need the thyroid meds they are on. While I would agree with the "most dogs" part I would tell you from a lot of years with Dobes that many Dobes (if not most) have thyroid issues and it almost always is hypothyroidism.
So since then when I want a complete thyroid panel we now send them to MSU--they really are the gold standard and generally less expensive that any place else.