Increased urinary excretion of sulfated 3,3',5-triiodothyronine in patients with nodular goiters receiving suppressive thyroxine therapy.
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.
Huang
W S
WS
Department of Nuclear Medicine, Tri-Service General Hospital, Taipei, Taiwan, R.O.C.
Kuo
S W
SW
Chen
W L
WL
Fuh
M M
MM
Wu
S Y
SY
D000328:Adult; D003404:Creatinine / Q000652:urine; D005260:Female; D006044:Goiter, Nodular / Q000188:drug therapy / Q000652:urine*; D006801:Humans; D007457:Iodine Radioisotopes; D008875:Middle Aged; D011863:Radioimmunoassay; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000009:adverse effects* / Q000097:blood / Q000627:therapeutic use; D014285:Triiodothyronine, Reverse / Q000652:urine*
D007457:Iodine Radioisotopes; D014285:Triiodothyronine, Reverse; D013972:Thyrotropin; D003404:Creatinine; D013974:Thyroxine