A study of untreated Graves' patients with undetectable TSH binding inhibitor immunoglobulins and the effect of anti-thyroid drugs.

OBJECTIVE

We previously reported the clinical characteristics of Graves' disease with undetectable TSH binding inhibitor immunoglobulins (TBII) at first visit, but a study of the prognosis of untreated TBII negative patients with anti-thyroid drug medication has never been undertaken. The aim of this paper is to study the difference between negative and positive TBII Graves' disease in relation to the effect of anti-thyroid drug treatment.

PATIENTS

From January 1986 to April 1991, 1545 patients with untreated Graves' disease were referred to Kuma Hospital, Kobe, Japan. Of these, 94 TRAb negative patients were identified. Another 83 TRAb positive patients were randomly selected from the other Graves' disease patients and served as a comparison group. Fifty-six of the 94 patients in the TBII negative group and 52 of the 83 patients in the TBII positive group completed treatment with methimazole only.

MEASUREMENTS

The trial was conducted as a retrospective study with a maximum treatment period of 36 months and a follow-up period of a further 12 months. From the original pool of patients, we classified 56 TBII negative patients into two groups according to the clinical course taken; Group A in whom TBII remained undetectable throughout methimazole treatment (9 men and 34 women, age 37.2 +/- 2.2 years), and Group B who became TBII positive (4 men and 9 women, 31.2 +/- 4.4 years). Fifty-two TBII positive patients served as the comparison Group C (8 men and 44 women, age 38.1 +/- 2.0 years).

RESULTS

Serum free T4 and free T3 levels in groups A and B were significantly lower before treatment than those of Group C (P < 0.001). The thyroid volumes of Group A and B patients were significantly smaller than those of Group C (P < 0.01). The level of TBII in Groups A and B was significantly lower than that in Group C (8.3 +/- 0.7 and 8.8 +/- 1.1 vs 57.0 +/- 2.8%, respectively, P < 0.001). The level of thyroid stimulating antibody (TSAb) in Groups A and B was significantly lower than that in Group C (478 +/- 71.0 and 761 +/- 140.3 vs 2143 +/- 280%, respectively, P < 0.01), and there were no significant differences in TSAb activities between Groups A and B. The remission rates in Groups A, B and C were 77.4, 36.4 and 36.5%, respectively. These data indicate that Group A has a good prognosis, but Group B has the same prognosis as Group C.

CONCLUSION

We conclude that patients in whom TSH binding inhibitor immunoglobulins remained negative have a much better prognosis than TSH binding inhibitor immunoglobulins positive patients or those who become TSH binding inhibitor immunoglobulins positive, having been initially negative.