Preparation of patients with thyroid cancer for 131I scintigraphy or therapy by 1-3 weeks of thyroxine discontinuation.
To assess whether the patient preparation procedure for (131)I scintigraphy could be streamlined, we evaluated the time course of thyroid-stimulating hormone (TSH) elevation after total thyroidectomy or after discontinuation of thyroxine (T(4)) in patients with thyroid cancer.


METHODS
The clinical records of 284 patients with well-differentiated thyroid cancer were reviewed. All patients had undergone total thyroidectomy. Two groups of patients were evaluated. The immediate postoperative group consisted of 176 patients who were not given thyroid hormone replacement after surgery because of planned postoperative (131)I therapy. The surveillance group consisted of 108 patients in whom T(4) replacement was stopped (without triiodothyronine [T(3)] replacement) in preparation for surveillance whole-body (131)I scintigraphy. We recorded the first TSH measurement and number of days after surgery or without thyroid hormone for each patient.


RESULTS
In the immediate postoperative group, TSH levels obtained 6-65 d (median, 17 d) after surgery ranged from 18.2 to 194.8 micro IU/mL (median, 46.6 micro IU/mL). The TSH values exceeded 30 micro IU/mL in 89% of patients evaluated at 1-2 wk, in 88% of those evaluated at 2-3 wk, and in 90% of those evaluated after 3 wk. In patients discontinuing T(4) (without T(3) replacement), TSH levels obtained from 6 to 35 d (median, 20 d) later ranged from 23.4 to 214.5 micro IU/mL (median, 61.1 micro IU/mL). The TSH levels exceeded 30 micro IU/mL in 100% of patients evaluated at 1-2 wk, in 89% of those evaluated at 2-3 wk, and in 96% of those evaluated after 3 wk.


CONCLUSIONS
In most patients with thyroid cancer being prepared for (131)I imaging or therapy, a TSH level exceeding 30 micro IU/mL can be achieved by withdrawal of thyroid hormone therapy for 1-3 wk.
Grigsby
Perry W
PW
Department of Radiation Oncology, Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri, USA. pgrigsby@wustl.edu
Siegel
Barry A
BA
Bekker
Simon
S
Clutter
William E
WE
Moley
Jeffrey F
JF
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011182:Postoperative Care / Q000379:methods*; D011877:Radionuclide Imaging; D012189:Retrospective Studies; D013961:Thyroid Gland / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000528:radiation effects; D013964:Thyroid Neoplasms / Q000097:blood* / Q000000981:diagnostic imaging / Q000628:therapy*; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000008:administration & dosage*; D013997:Time Factors; D016896:Treatment Outcome; D028761:Withholding Treatment
D013972:Thyrotropin; D013974:Thyroxine