Standardized radioiodine therapy in Graves' disease: the persistent effect of thyroid weight and radioiodine uptake on outcome.
OBJECTIVE
To assess the incidence of hypothyroidism, euthyroidism, and recurrent hyperthyroidism following a standard dose of Na131I (3.7 MBq or 100 microCi) per g thyroid tissue, adjusted for radioiodine tracer uptake.


METHODS
A single-centre prospective follow-up study from January 1990 to December 1992.


METHODS
Academic Hospital in Utrecht, the Netherlands.


METHODS
Newly diagnosed patients with Graves' disease (n = 148).


METHODS
Radioiodine treatment at a standard dose of 3.7 MBq or 100 microCi per g thyroid tissue.


METHODS
Confidence interval testing of resulting thyroid status, defined by biochemical criteria.


RESULTS
The overall cure rate was 70% (103 of 148 subjects), confidence interval (CI) 62-77%. A 90% incidence of hypothyroidism was found in patients with a small thyroid (less than 20 g). Recurrent hyperthyroidism was found significantly more often in subjects with a thyroid weight exceeding 60 g compared to those who had a thyroid of 9-59 g. More recurrences were found in subjects in the highest tertile of a 24-h radioiodine uptake test (> 80% uptake) compared to those in the lowest tertile (< 60% uptake).


CONCLUSIONS
No uniform treatment results expressed per thyroid weight category were obtained, in spite of standardizing the treatment Na131I dose (3.7 MBq per g thyroid). Graves' patients with a thyroid smaller than 20 g and those with less than 60% 24-h radioiodine uptake have a 50-90% chance of hypothyroidism at the 12-month follow-up.
Department of Medicine, Academic Hospital Utrecht, Netherlands.
T W
TW
de Bruin
C D
CD
Croon
J M
JM
de Klerk
J W
JW
van Isselt
D000328:Adult; D005260:Female; D005500:Follow-Up Studies; D006111:Graves Disease / Q000503:physiopathology / Q000532:radiotherapy*; D006801:Humans; D007457:Iodine Radioisotopes / Q000008:administration & dosage / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D011446:Prospective Studies; D013961:Thyroid Gland / Q000378:metabolism / Q000503:physiopathology*; D016896:Treatment Outcome
D007457:Iodine Radioisotopes