[Treatment of Graves-Basedow's disease with 131I. Assessment of a "modulated fixed activity" protocol]

The purpose of this study was to retrospectively evaluate the hypothyroidism rate, persistence of hyperthyroidism and the complications after the administration of 131I in 3 cohorts defined according to the activity of 131I administered.

We consecutively treated 659 patients diagnosed with Graves-Basedow disease (GBD) with 131I. The activity was determined on the basis of a protocol that we called "modulated fixed activity". A total of 45 patients (Group 1) who had previously undergone surgery were given small 131I activities of between 111-185 MBq (3-5 mCi), 247 patients (Group 2) with normal or almost normal-sized thyroids were given activities of between 222-333 MBq (6-9 mCi) and the 367 patients with diffuse goiters (Group 3) activities of between 370-555 MBq (10-15 mCi).

A total of 69.2 % of the patients presented hypothyroidism at the end of the follow-up period. By groups, the percentages of hypothyroidism at the end of the follow-up period were 69 %, 68.8 % and 69.6 % respectively. The average time for the patients to present hypothyroidism was 2.7 years with a maximum de 12.3 years and a minimum of 2 months. No severe precocious complications after the administration of 131I were noted.

The choice of the modulated fixed doses of 131I for treatment of the GBD is a simple method and permit treatment in only one day.