Managing thyroid cancer without thyroxine withdrawal

Abstract

Thyroxine (T4) withdrawal or recombinant TSH is used for the stimulation of thyroglobulin (Tg), whole-body scanning (WBS) and iodine-131 treatment in patients with thyroid carcinoma. This study evaluated the T4 dose reduction protocol as an alternative for patients' preparation. Fifty-one patients were submitted to total T4 withdrawal for WBS and Tg measurement. T4 treatment was then resumed and maintained until TSH reached levels < 0.3 mIU/l. The T4 dose was then decreased to 0.8 microg/kg/day and TSH was measured weekly. Tg was assayed when TSH was > 30 mIU/l. Patients diagnosed with the disease upon initial evaluation were treated. We also evaluated the clinical and laboratory changes observed for both preparations. Using the reduced dose protocol, TSH levels > 30 mIU/l were reached within 6 and 8 weeks in 84.6 and 100% of the patients, respectively. T4 withdrawal was associated with more common symptoms of hypothyroidism and elevation of creatine kinase (CK) and LDL cholesterol. The T4 dose reduction protocol proved to be useful for Tg stimulation and ablative therapy, without the complication of severe hypothyroidism or the cost of recombinant TSH.

Three Weeks Withdrawal of T4 Prior to I131 whole Body Scan Can Achieve the Required Serum TSH Level with Significantly Less Hypothyroidism

“…The striking finding in the current study was the profound elevation of serum TSH level after 3 weeks of T4 withdrawal much more than the desired 30 mIU/L (mean=77.4±27.9) in 98% of patients in group I. Our findings are keeping with the results of Rosario et al who stated that serum TSH levels > 30 mIU/L were reached in 78.4 and 100% of patients in the absence of thyroid hormone within 2 and 3 weeks, respectively (19) . Similarly, Grigsby et al reported that in most patients with cancer thyroid being prepared for I131 imaging or therapy, a TSH level > 30 mIU/L can be achieved by withdrawal of thyroid hormone therapy for 1-3 weeks (20) .…”