Thyroid volume and function after 131I treatment of diffuse non-toxic goitre.

OBJECTIVE: Traditional treatment of diffuse non-toxic goitre are thyroid hormone suppression or surgery. When treating nodular non-toxic goitre with 131I treatment a reduction in thyroid volume to about 50% has been observed. In the present study we evaluated the effect of 131I treatment of diffuse non-toxic goitre.

DESIGN: Retrospective study of patients treated for a diffuse non-toxic goitre and followed by evaluation of thyroid volume measured by ultrasound.

PATIENTS: Ten selected patients from our out-patient clinic with diffuse non-toxic goitre.

MEASUREMENTS: Thyroid volume was measured by ultrasound and thyroid function by serum values of T4, T3, T3 uptake ratio, TSH, TSH receptor antibodies and thyroid peroxidase antibodies (anti-TPO). Measurements were performed before and 1, 3, 6 and 12 months (and 18 months (n = 7), thyroid volume measured in six patients)) after 131I treatment.

RESULTS: Thyroid volume declined in all patients from median 41 (range 27-160) ml to 20 (range 9-108) ml over 1 year, a reduction of 47%. One patient developed transient and one persistent hypothyroidism in the follow-up period. Both had elevated anti-TPO levels before treatment (331 and 9185 U/ml) and demonstrated titre increases of 2.5 and 30 times after 3 and 6 months, respectively. Pretreatment values were reached after 1 year. The other eight patients had normal anti-TPO levels and free T4 and T3 indices did not change during follow-up, whereas serum TSH levels demonstrated upward trends within the normal range (P < 0.05). TSH receptor antibodies were normal and remained so in all patients.

CONCLUSIONS: 131I treatment of diffuse non-toxic goitre reduces thyroid volume by approximately 50% within 12-18 months. Hypothyroidism, during a limited follow-up period, developed only in patients with positive anti-TPO levels before treatment.