Thyroid ablation
leads to disappearance of antithyroid antibodies in patients with
thyroid cancer
(November 2003)
The background of
the study. Many people have high serum titers or concentrations
of one or more thyroid antibodies; but whether continued production
of these antibodies is dependent on the presence of thyroid tissue
is not clear. In this study the effect of complete elimination of
thyroid tissue on the production of thyroid antibodies was determined.
How the study was done. The study
subjects were 182 patients with papillary or follicular thyroid
carcinoma who had high serum titers of thyroid peroxidase or thyroglobulin
antibodies. All the patients underwent thyroidectomy, followed by
radioiodine and then thyroxine (T4) therapy. Thereafter, the patients
were evaluated for recurrent tumor and had measurements of the antibodies
annually. Complete thyroid destruction was defined as two consecutive
negative whole-body radioiodine scans and a serum thyroglobulin
concentration <3 µg/L. Disappearance of serum antibodies
was defined as a negative test for the particular antibody during
temporary cessation of thyroxine therapy.
The results of the study. At base
line, 94 percent of the patients had a high serum titer of antithyroid
peroxidase antibodies, and 64 percent had a high serum titer of
antithyroglobulin antibodies; 58 percent had a high serum titer
of both antibodies.
The average duration of follow-up was 10 years; 59 percent of the
patients were followed for 8 years, and 38 percent for 12 years;
4 patients (2 percent) died from thyroid carcinoma. The serum titers
of both antibodies decreased gradually in all patients after initial
treatment; the median time to disappearance of serum antithyroid
peroxidase antibodies was 6.3 years, and the median time to disappearance
of serum antithyroglobulin antibodies was 3.0 years. The median
time to disappearance of all thyroid tissue was 2.8 years. During
follow-up, patients in whom normal or abnormal thyroid tissue was
present were more likely to have high serum titers of the antibodies.
The conclusions of the study. In
patients with thyroid carcinoma, complete ablation of thyroid tissue
results in gradual disappearance of serum antithyroid antibodies.
The original article. Chiovato L, Latrofa F, Braverman LE, Pacini
F, Capezzone M, Masserini L, Grasso L, Pinchera A. Disappearance
of humoral thyroid autoimmunity after complete removal of thyroid
antigens. Ann Intern Med 2003;139:346-51.
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