title: Factors predicting hypothyroidism in long-term follow-up after 131I therapy.
abstract: 187 patients, euthyroid for more than a year after radioiodine treatment for hyperthyroidism, were studied for 10 years; 81 (43%) became hypothyroid. The incidence of hypothyroidism was lower in patients initially presenting with large thyroids (28%) or with nodular thyroids (22%) and in those without thyroid autoantibodies (31%). During follow-up, an elevated serum TSH was present in all 81 patients when they became hypothyroid (sensitivity and negative predictive value 100%), and was present for at least a year in 98% of these. However, an elevated serum TSH was also present in 48% of 106 patients remaining euthyroid (positive predictive value 61%). FT4I was low in 94% of patients who became hypothyroid and normal in 80% of patients who remained euthyroid (positive predictive value 78%, negative predictive value 93%). Serum TSH and FT4I were the best biochemical predictors. FT3I and serum cholesterol were less satisfactory. A palpable thyroid becoming impalpable, though readily assessed, was limited in usefulness. Clinical appraisal remains important and a progressive, though perhaps less rapid, later increase in the incidence of hypothyroidism appears likely.
authors.affiliation: Department of Nuclear Medicine, Royal Liverpool Hospital, England.
authors.forename: T M
authors.initials: TM
authors.lastname: Gimlette
authors.forename: M
authors.initials: M
authors.lastname: Critchley
authors.forename: C R
authors.initials: CR
authors.lastname: Squire
mesh_terms: D000368:Aged; D005500:Follow-Up Studies; D006801:Humans; D006980:Hyperthyroidism / Q000532:radiotherapy*; D007037:Hypothyroidism / Q000175:diagnosis* / Q000209:etiology; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008875:Middle Aged; D011379:Prognosis; D013997:Time Factors
chemical_list: D007457:Iodine Radioisotopes