Long-term effect of radioactive iodine on thyroid function and size in patients with solitary autonomously functioning toxic thyroid nodules.
OBJECTIVE
To investigate the long-term effects of radioiodine (131I) on thyroid function and size in patients with a solitary toxic thyroid nodule.


METHODS
Prospective study of patients treated for a solitary autonomous toxic nodule, followed by evaluation of thyroid volume and function.


METHODS
Sixty-two consecutive patients followed for a minimum of 12 months (range 12-168, median 60). Seventeen patients received antithyroid drug treatment before 131I.


METHODS
Standard thyroid function variables and ultrasonically determined thyroid volume before as well as 0.75, 1.5, 3, 6 and 12 months after treatment, and then once a year were investigated.


RESULTS
131I treatment (3.7 MBq/g thyroid tissue corrected to a 100% 24-h 131I uptake) was given as a single dose in 53 patients; six needed two doses and another three were given 3-5 131I treatments. The median initial dose was 310 MBq (140-666) and the median total dose was 332 MBq (148-1576). In patients receiving one 131I treatment (n = 53) the total thyroid volume decreased significantly from a median of 40 ml (range 19-77) to 24 ml (8-50) within 3 months. This represented a median reduction of 35%. A further significant decrease was seen after 24 months to a total reduction of 45%. In patients given more than one dose the thyroid volume was reduced from a median of 45 ml (19-104) before treatment to 30 ml (14-50) after a follow-up of 60 months (9-132) after the last 131I treatment. Patients without antithyroid pretreatment, receiving one 131I treatment (n = 39) became euthyroid after a median of 1.5 months (0.75-9) after treatment. Seventy-five per cent were euthyroid within 3 months. In patients pretreated with antithyroid drugs and treated with one dose of 131I (n = 14) euthyroidism was achieved after a median of 12 months (0.75-24) after 131I treatment. Hypothyroidism developed in five patients (8%) after a median of 36 months (6-60) after 131I treatment.


CONCLUSIONS
A cure-rate of 75% within 3 months is seen when treating autonomous solitary toxic thyroid nodules with 131I. The thyroid volume is reduced by 35% within 3 months and 45% after 2 years. Side-effects are few and consist of hypothyroidism in less than 10% with a median follow-up of 5 years. This treatment should be regarded as the standard treatment for this condition until prospective comparisons with surgery and ethanol injection therapy have been performed.
Department of Endocrinology, Herlev Hospital, University of Copenhagen, Denmark.
B
B
Nygaard
L
L
Hegedüs
K G
KG
Nielsen
P
P
Ulriksen
J M
JM
Hansen
D000328:Adult; D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013961:Thyroid Gland / Q000473:pathology / Q000503:physiopathology / Q000528:radiation effects*; D016606:Thyroid Nodule / Q000473:pathology / Q000503:physiopathology / Q000532:radiotherapy*; D013997:Time Factors; D016896:Treatment Outcome
D007457:Iodine Radioisotopes