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Long‐term effect of radioactive iodine on thyroid function and size in patients with solitary autonomously functioning toxic thyroid nodules
Author(s) -
Nygaard Birte,
Hegedüs Laszlo,
Gerhard Nielsen Kamilla,
Ulriksen Peter,
Hansen Jens Mølholm
Publication year - 1999
Publication title -
clinical endocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 147
eISSN - 1365-2265
pISSN - 0300-0664
DOI - 10.1046/j.1365-2265.1999.00635.x
Subject(s) - medicine , endocrinology , thyroid function , thyroid , iodine , radioactive iodine , term (time) , thyroid nodules , thyroid function tests , chemistry , physics , organic chemistry , quantum mechanics
OBJECTIVE To investigate the long‐term effects of radioiodine ( 131 I) on thyroid function and size in patients with a solitary toxic thyroid nodule. DESIGN Prospective study of patients treated for a solitary autonomous toxic nodule, followed by evaluation of thyroid volume and function. PATIENTS Sixty‐two consecutive patients followed for a minimum of 12 months (range 12–168, median 60). Seventeen patients received antithyroid drug treatment before 131 I. MEASUREMENTS 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 131 I treatment (3.7 MBq/g thyroid tissue corrected to a 100% 24‐h 131 I uptake) was given as a single dose in 53 patients; six needed two doses and another three were given 3–5 131 I treatments. The median initial dose was 310 MBq (140–666) and the median total dose was 332 MBq (148–1576). In patients receiving one 131 I 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 131 I treatment. Patients without antithyroid pretreatment, receiving one 131 I 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 131 I ( n = 14) euthyroidism was achieved after a median of 12 months (0.75–24) after 131 I treatment. Hypothyroidism developed in five patients (8%) after a median of 36 months (6–60) after 131 I treatment. CONCLUSION A cure‐rate of 75% within 3 months is seen when treating autonomous solitary toxic thyroid nodules with 131 I. 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.