3,5,3'-Triiodothyroacetic acid minimizes the pituitary thyrotrophin secretion in patients on levo-thyroxine therapy after ablative therapy for differentiated thyroid carcinoma.
The aim of this study was to examine the influence of 3,5,3'-triiodothyroacetic acid (TRIAC) on serum thyrotrophin (TSH) concentration in 25 patients on levo-thyroxine (L-T4) therapy after ablative therapy for differentiated thyroid carcinoma. The daily L-T4 intake amounted to 2.6 +/- 0.7 micrograms/kg body weight (+/- SD). Serum TSH concentration was determined by means of a sensitive radioimmunometric method (lower detection limit 0.03 mU/l). The median (means) basal TSH concentration under L-T4 amounted to 0.11 mU/l (range less than 0.03 mU/l-7.39 mU/l). During supplementary intake of 500 micrograms TRIAC daily the median basal TSH decreased to 0.04 mU/l range less than 0.03 mU/l-0.24 mU/l; P less than 0.0003). The TRIAC-induced decrease in 17 out of 20 basal TSH-concentrations exceeding 0.03 mU/l ranged from 38% to as much as 98%. TRIAC reduced the median TRH-stimulated TSH concentration from 0.25 mU/l (range less than 0.03 mU/l-47.3 mU/l) to 0.04 mU/l (range less than 0.03 mU/l-1.43 mU/l; P less than 0.0001). A blunted TSH-response to TRH occurred in 8.7% prior to and in 52% of the patients during TRIAC medication. Side effects such as nervousness, cardiac arrhythmia or tachycardia under supplementary TRIAC (500 micrograms daily) were observed in four patients. The conclusion is that the supplementary medication of 500 micrograms TRIAC daily in euthyroid patients on L-T4 medication after thyroid gland ablation for differentiated thyroid cancer is an effective means to minimize serum-TSH concentration.
D000328:Adult; D000368:Aged; D003864:Depression, Chemical; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010902:Pituitary Gland / Q000187:drug effects; D013964:Thyroid Neoplasms / Q000532:radiotherapy / Q000601:surgery*; D013972:Thyrotropin / Q000097:blood*; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology; D013974:Thyroxine / Q000627:therapeutic use*; D014284:Triiodothyronine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use
D014284:Triiodothyronine; C010642:3,3',5-triiodothyroacetic acid; D013973:Thyrotropin-Releasing Hormone; D013972:Thyrotropin; D013974:Thyroxine