Excerpt from Medpage Today - Full Thyroid Removal May be Best in Graves' Disease...
"Removing the whole thyroid lessens the chance of hyperthyroidism recurrence in Graves' disease compared with partial thyroidectomy, but it also leads to increased temporary hypoparathyroidism, researchers found."
"Overall, they evaluated four trials totaling 674 patients with Graves' disease -- 342 of whom had total thyroidectomy, 332 who'd had subtotal thyroidectomy.
They found that total thyroidectomy was associated with a significant reduction in recurrent hyperthyroidism compared with the subtotal procedure (relative risk 0.14, 95% CI 0.05 to 0.41).
"It seems that leaving any tissue could be a risk of recurrence, just as some endocrine surgeons believe," the researchers wrote.
However, overall rates of ophthalmopathy progression were similar between the two groups."
With Graves Disease, the thyroid produces too much thyroid hormone. Levo is given when the thyroid does not produce enough, so apparently, you were hypo before your TT, which means you wouldn't have had Graves Disease. Since you no longer have a thyroid, there's nothing to produce too much hormones except the medication you take on a daily basis, so, no, you can't develop Graves Disease after TT, but you "can" be over medicated.
Why did you have your thyroid removed and how long ago? Were you ever tested for thyroid antibodies prior to your thyroidectomy?
What were your TSH levels prior to your surgery? What are your TSH levels now? Have you "ever" had a Free T3 and/or Free T4 or even a Total T3 and/or Total T4? T3 and T4 are the actual thyroid hormones and give a much better picture of actual thyroid hormone status than TSH...
Your symptoms are, both, hyper and hypo (dry, itchy skin is, typically, a symptom of hypothyroidism, rather than hyperthyroidism), but you can't know without testing for Free T3 and Free T4... TSH is often suppressed, even when one is still has hypo symptoms or is adequately medicated. You should insist that your doctor orders those tests and if s/he refuses, don't hesitate to find another doctor. There "are" doctors out there who will test properly.
Hyperpigmentation can also be caused by hemochromatosis (excessive iron) or Addison's Disease (adrenal condition), also, so you should talk to your doctor and insist on proper testing to rule out other causes.