Outcome of radioiodine-131 therapy in hyperfunctioning thyroid nodules: a 20 years' retrospective study.
OBJECTIVE
To investigate the risk of hypothyroidism after radioiodine (131I) treatment for hyperfunctioning thyroid nodules.


METHODS
Retrospective analysis of patients treated with 131I for hyperfunctioning thyroid nodules and followed up for a maximum of 20 years.


METHODS
A total of 346 patients treated with 131I in the years 1975-95, for a single hyperfunctioning nodule.


METHODS
Hypothyroidism was defined as TSH levels > 3.7 mU/l. Kaplan-Meier survival analysis was used to analyse permanence of euthyroidism after 131I. A stepwise Cox proportional hazard model was used to identify factors influencing the progression to hypothyroidism.


RESULTS
The cumulative incidence of hypothyroidism was 7.6% at 1 year, 28% at 5 years, 46% at 10 years and 60% at 20 years. Age (P < 0.01), 24-th 131I uptake (P < 0.05) and previous treatment with methimazole (MMI, P < 0.1) were associated with a faster progression towards hypothyroidism, while thyroid and nodule size, thyroid status at diagnosis and degree of extranodular thyroid parenchymal suppression had no influence. In hyperthyroid patients with partial parenchymal suppression, however, previous MMI treatment was the most important prognostic factor (P < 0.01).


CONCLUSIONS
After 20 years of follow-up, 60% of patients treated with 131I for a single hyperfunctioning nodule are hypothyroid. Factors increasing the risk of hypothyroidism are age, 131I uptake and MMI pretreatment. The prognostic value of this last factor, however, depends on the degree of suppression of the extranodular thyroid parenchyma at the scan.
Ceccarelli
Claudia
C
Department of Endocrinology, University of Pisa, Opsedale Cisanello, Pisa, Italy. claudiac@endoc.med.unipi.it
Bencivelli
Walter
W
Vitti
Paolo
P
Grasso
Lucia
L
Pinchera
Aldo
A
D000328:Adult; D000367:Age Factors; D000368:Aged; D013956:Antithyroid Agents / Q000009:adverse effects; D018450:Disease Progression; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D006980:Hyperthyroidism / Q000532:radiotherapy*; D007037:Hypothyroidism / Q000209:etiology; D007457:Iodine Radioisotopes / Q000009:adverse effects / Q000627:therapeutic use*; D008297:Male; D008713:Methimazole / Q000009:adverse effects; D008875:Middle Aged; D011832:Radiation Injuries / Q000209:etiology; D013961:Thyroid Gland / Q000502:physiology; D016606:Thyroid Nodule / Q000532:radiotherapy*; D013972:Thyrotropin / Q000097:blood; D016896:Treatment Outcome
D013956:Antithyroid Agents; D007457:Iodine Radioisotopes; D008713:Methimazole; D013972:Thyrotropin