Well, my Doctor just did fairly basic blood and urine tests; he said he wanted to make sure my cholesterol and blood pressure weren't astronomical, that I wasn't extremely obese, and that there were no liver or other issues that could present a problem. Unlike many that I've read about, he wasn't terribly concerned with establishing a baseline before starting; he started me on a fairly conservative dosage for my height & weight, checked up at three months, and at six months will do a full panel of tests to see what my levels are. Based on those levels, he'll make any necessary changes to my dosages.
I don't know what specific numbers would have been an issue, but I got the impression that as long as nothing really jumped out at him, there wouldn't be a problem.
I don't know how typical my experience was; the whole thing seemed pretty laid-back, but he has been involved in the transition of over 40 people, so I have to assume he knows what he's doing. I wonder sometimes if some of the endos I've heard of with really extreme requirements might have little experience dealing with TS issues, and are making up for it with an overabundance of caution. Just a thought...
Annie