triiodothyronine--reverse and Goiter--Nodular

Increased serum 3,3',5-triiodothyronine sulfate (T3S) levels have been detected in various pathophysiologic states. However, little is known about T3S concentrations in other biological fluids. By employing a highly sensitive, specific, and reproducible radioimmunoassay (RIA), we measured T3S in the serum and urine of 20 premenopausal women with benign nodular goiters before and after administration of thyroxine for 6 months (T4; 3.2 micrograms/kg/day). Serum T3 concentrations did not change significantly after treatment (2.0 vs. 1.7 nmol/L; p > 0.05). However, the mean serum T4 and free T4 concentrations were significantly higher after treatment (138 vs. 88 nmol/L and 28 vs. 17 pmol/L; p < 0.01, respectively). Serum thyroid stimulating hormone (TSH) levels were significantly reduced after T4 treatment (0.13 vs. 0.66 mU/L, p < 0.01) and the serum levels of T3S were significantly increased after treatment (82 vs. 45 pmol/L; p < 0.01). A good correlation was observed between increased serum T3S and T4 concentrations (r = 0.66; p < 0.001). The sulfoconjugate of T3 was significantly increased in creatinine-corrected urine after treatment (606 vs. 253 pmol/umol Cr.; p < 0.01). There was a significant correlation between increased creatinine-corrected urine T3S and increased serum free T4 (r = 0.65; p < 0.001). In summary, significant increases in serum and urine T3S levels were noted in T4-treated patients with subnormal serum TSH and borderline elevated T4. We thus conclude that the sulfation pathway may play a role in the homeostasis of thyroid hormone metabolism in T4-treated subjects with relative hyperthyroxinemia. In addition, the creatinine-corrected urine concentrations of T3S may serve as an index for the evaluation of T4-treated patients with elevated levels of T4.

Topics: Adult; Creatinine; Female; Goiter, Nodular; Humans; Iodine Radioisotopes; Middle Aged; Radioimmunoassay; Thyrotropin; Thyroxine; Triiodothyronine, Reverse

The secretion rates of T4, T3, and rT3 were studied in experiments of short duration by a new method based on determinations of the hormone difference across the thyroid combined with simultaneous electromagnetic thyroid blood flowmetry during surgery in 70 euthyroid patients. The secretion rate of T3 was similar in normal thyroid tissue and nodular goitre, but those of T4 and rT3 were lower in nodular goitre and solitary adenoma (P less than 0.05). In 61 patients with normal thyroid tissue or nodular goitre the secretion rates during surgery (mean +/- SEM) were for T4 222 +/- 28 nmol/day, for T3 27.4 +/- 3.1 nmol/day, and for rT3 3.5 +/- 0.5 nmol/day. In relation to the individual T4 secretion rate, the secretion rate of T3 was 12.5 +/- 3.0% and that of rT3 1.2 +/- 0.9%. In these short-term experiments we found a secretion rate for T4 during operation about 50% greater than in earlier long-term kinetic studies, but which tallied with a recent report using a 4-compartment model. For T3 and rT3 it was 2-3 times greater than earlier estimates. The secretion was estimated to be 50% of the total production rate for T3 and 6% for rT3. If proportional adjustment were performed to yield a T4 secretion of about 130 nmol/day. T3 and rT3 secretion rates would still be greater than earlier reported.

Topics: Adenoma; Adult; Aged; Carcinoma; Electromagnetic Phenomena; Female; Goiter; Goiter, Nodular; Humans; Hyperparathyroidism; Intraoperative Period; Male; Middle Aged; Rheology; Surgical Procedures, Operative; Thyroid Gland; Thyroid Neoplasms; Thyroxine; Triiodothyronine; Triiodothyronine, Reverse