SERIAL TSH DETERMINATION AFTER T3 WITHDRAWAL OR THYROIDECTOMY IN THE THERAPY OF THYROID-CARCINOMA

  • 1 January 1979
    • journal article
    • research article
    • Vol. 20  (9) , 928-932
Abstract
Exogenous triiodothyronine (T3) was substituted for levothyroxin or desiccated thyroid in 13 athyrotic patients previously treated for papillary, follicular or mixed papillary-follicular carcinoma of the thyroid. After 4 wk, T3 therapy was discontinued and serial determinations of plasma thyroid stimulating hormone (TSH) concentrations were made. A roughly exponential rise in TSH values, corresponding to a doubling time of 2 days, was observed until a level of 40 .mu.IU/ml was reached, after which the curve passed through a maximum at 20 days. The mean time required for a level of 50 .mu.IU/ml was 11 days, and this time is suggested for TSH determination before 131I imaging of patients with thyroid cancer. Plasma TSH values in 8 patients following total thyroidectomy showed a much slower and more variable rise, with a mean doubling time of 7.6 days. Weekly TSH levels beginning at 15 days will provide a rational basis for 131I imaging in this group, in whom a longer period of hypothyroidism will be required before imaging and therapy. Adherence to these protocols should minimize the duration of hypothyroidism in patients undergoing 131I treatment of thyroid carcinoma.

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