Thyroid hormones homeostasis and TSH in autonomic thyroid nodule

Thirty patients with autonomic thyroid nodules were studied. Thyroid scintigram, iodine uptake at 2 and 24 hrs, PBI, total thyroxine, serum T3(RIA), basal TSH and 30 minutes after TRH administration were performed. A lack of concordance was found between the clinical signs and the laboratory data. According to the data obtained the patients were grouped into 3 categories: having 1) autonomic thyroid nodules with normal PBI, T4t, T3 values and absent or diminished TSH response to TRH; 2) autonomic thyroid nodules with increased T3 secretion and no response to TRH despite a normal T4 and iodine uptake, 3) hyperfunctional autonomic nodules in which PBI, T4t, T3 and iodine uptake are increased. TSH response to TRH is the most sensitive test for hyperthyroidism, more sensitive than the circulating thyroid hormones assay, and best fitted for adequate therapeutic management. Serum triiodothyronine was found to be increased in 95% of the patients. Thus, there is a T3 thyreotoxicosis in most of the autonomic nodules. TRH test and serum T3 assay being essential elements in starting the treatment, they have to be included among the tests used in autonomic thyroid nodules investigation.