The usefulness of a sensitive thyrotrophin assay in the fine adjustment of thyroxine therapy following ablation for carcinoma.
The usefulness of FT4 and FT3 measurements as an index of adequate thyroxine treatment in differentiated thyroid cancer was evaluated in 25 athyreotic patients on two occasions with an interval of at least 6 months. The determinations were combined with a TRH test. The TSH measurements were performed using a sensitive immunoassay. The great interindividual differences in absorption and metabolism of thyroxine made the measurements of FT4 and FT3 unsuitable for fine adjustment of thyroxine substitution therapy. When all patients are divided into 4 categories according to their TRH test (1: delta TSH less than or equal to 1 mU/l; 2: greater than or equal to 1 less than or equal to 4 mU/l; 3: greater than 4 mU/l and 4: basal TSH greater than or equal to 6 mU/l), there is a considerable overlap between these categories in relation to FT4 and FT3. In the second TRH test all patients were found to belong to the same category when their thyroxine dose had not been changed. A basal TSH level below 0.30 mU/l suggests nearly complete suppression of TSH secretion. However, a TRH test is necessary to allow a definite conclusion to be drawn. It is argued that complete suppression of TSH is not necessarily desirable in patients with treated thyroid carcinoma. From the results of our study it would seem advisable to use the TRH test once to adjust the thyroxine dose in such a manner that subnormal basal TSH is achieved as in the second category. Once the dosage has been established, a determination of basal TSH suffices in follow-up.
de Lange
W E
WE
Sluiter
W J
WJ
Doorenbos
H
H
D000328:Adult; D000368:Aged; D003131:Combined Modality Therapy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D011863:Radioimmunoassay; D013964:Thyroid Neoplasms / Q000097:blood / Q000628:therapy*; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000097:blood / Q000627:therapeutic use*
D013972:Thyrotropin; D013974:Thyroxine