Changes in TSH-receptor antibody (TR-Ab) and thyroid stimulating antibody (TS-Ab) after thyroidectomy were examined in seventeen thyrotoxic patients (3 males and 14 females, 40.0±3.4yr) with positive TR-Ab and TS-Ab.
They were subjected to thyroid surgery because of suspected malignancy, methymazole induced agranulocytosis, cardiac failure, recurrent gastric ulcer or emotional instability. Of these patients, 3 were totally thyroidectomized, 11 were subtotally thyroidectomized and 3 were unilaterally lobectomized. Histological findings in these patients showed diffuse hyperplasia in 8 cases, an adenomatous goiter in 3, diffuse hyperplasia plus follicular adenomas in 5, and Hashitoxicosis in one.
Their thyroid function before surgery was as follows: T
3, level, 3.9±0.7ng/ml; T
4, 19.5±3.3μg/dl; free T
3, 11.9±1.2pg/ml; free T
4, 4.9±1.0ng/dl; and TSH, 0.9±0.1μU/ml. Mean levels of TR-Ab and TS-Ab before surgery were 56.8±4.6% and 1,218.6±262.4%, respectively. Positive anti-thyroid antibody (TGHA) was 47.0%, positive anti-microsomal antibody (MCHA) was 88.2% in these thyrotoxic patients, and mean levels of TGHA and MCHA were 1,688±715 and 89,280±34,717 times, respectively.
After the operation, these parameters were decreased and their thyroid functions became an euthyroid or a hypothyroid state one month later.
The incidence of post-operative hypothyroidism was 45.5% in subtotally thyroidectomized patients, 33.3% in unilaterally lobectomized patients and 100% in totally thyroidectomized patients. TR-Ab levels decreased from 56.2±6.5% before surgery to 24.5±12.2% 12 months after surgery, but increased again to 35.0±15.7% 24 months after surgery in subtotally thyroidectomized patients. These levels also decreased from 50.4±11.0% before surgery to 37.8±11.4% 12 months after surgery, and remained unchanged to 38.2±10.4% 24 months after surgery in unilaterally lobectomized patients. On the other hand, in totally thyroidectomized patients, TR-Ab levels decreased and normalized 12 months after surgery. One of subtotally thyroidectomized or unilaterally lobectomized patients developed recurrent thyrotoxicosis with an increased positive TR-Ab. Mean levels of TS-Ab decreased to 28.3±181.3% and 152.5±47.9% 12 and 24 months after surgery, respectively, in subtotally thyroidectomized patients. These levels decreased 12 months after surgery and then increased again to 303.6±130.6% in unilaterally lobectomized patients. On the other hand, TS-Ab levels decreased and normalized to 94.3±3.9% 6 months after surgery in totally thyroidectomized patients. Although mean levels of TGHA and MCHA titers decreased noticeably after surgery in both totally and subtotally thyroidectomized patients, these levels decreased slightly in unilaterally lobectomized patients.
These data suggest that decreases in TR-Ab and TS-Ab after thyroidectomy in thyrotoxic patients may be related to the mass volume of the remaining hyperplastic tissue of the thyroid.
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