24-h 131I Uptake Research Articles

Radioiodine therapy in elderly patients with subclinical hyperthyroidism due to non-voluminous nodular goiter and its effect on bone metabolism

To evaluate 131I therapy in elderly patients with subclinical hyperthyroidism (SCH) due to nodular disease and who did not receive antithyroid drugs (ATDs), and the effect of the treatment on bone metabolism. Thirty-six patients with TSH ≤ 0.1 mIU/L and non-voluminous goiter (< 60 cm³) were studied. Bone mineral density (BMD) was assessed in 17 women with osteopenia. Mean 24-h 131I uptake was 17.5%. Symptoms of thyrotoxicosis were reported by two (5.5%) patients in the first week after therapy. One year after radioiodine treatment, SCH was resolved in 30 (83.3%) patients, and hypothyroidism was detected in one (2.7%). In the patients in whom TSH returned to normal, femoral and lumbar spine BMD increased by 1.9% and 1.6%, respectively, in average. In elderly patients with SCH and non-voluminous goiter, radioiodine not preceded by ATDs is a safe and effective therapeutic alternative. Resolution of SCH has beneficial effects on BMD in postmenopausal women with osteopenia.

Effect of lifelong iodine supplementation on thyroid 131-I uptake: a decrease in uptake in euthyroid but not hyperthyroid individuals compared to observations 50 years ago

In Sweden, iodine has been added to table salt (10 mg/kg) since 1936; this amount was increased in 1966 to 50 mg/kg. To investigate a euthyroid Swedish population (n = 44, 60-65 years) with its entire lifespan with iodine supplementation as for 24-h 131-I uptake (24 h IU) and thyroid nodularity (thyroid scintigraphy). To compare the euthyroid 24 h IU with uptake of thyrotoxic individuals, and with observations from 1955. The 24 h IU was used in euthyroid individuals after oral administration of 0.1 MBq/2.7 microCi radioiodine and imaging of the thyroid gland was carried out using 99mTc-pertechnetate. In 1999-2000, the mean 24 h IU in the euthyroid individuals was 21% (range 11-33%) and the normal (central 95%) reference interval was 14-30%. Scintigraphy suggested multinodular goitre in three euthyroid individuals. In Graves' patients (n = 53, 50-65 years), the mean 24 h IU was 61% (range 29-89%). In 1955, the 24 h IU in euthyroid individuals was higher (38%, range 10-70%), while hyperthyroid patients had uptake values similar to those recorded in the present investigation (mean 62%, range 40-90%). The population sample studied had to be small for ethical reasons. We conclude that the reference interval for 24 h IU is 14-30% in this population that had spent its entire lifespan with iodine supplementation. This is lower than that recorded in a Swedish euthyroid population half a century ago having had low-grade table-salt iodine supplementation for 20 years. Values for hyperthyroid patients, however, do not appear to have been affected likewise.

Long-term effect of radioactive iodine on thyroid function and size in patients with solitary autonomously functioning toxic thyroid nodules.

To investigate the long-term effects of radioiodine (131I) on thyroid function and size in patients with a solitary toxic thyroid nodule. Prospective study of patients treated for a solitary autonomous toxic nodule, followed by evaluation of thyroid volume and function. Sixty-two consecutive patients followed for a minimum of 12 months (range 12-168, median 60). Seventeen patients received antithyroid drug treatment before 131I. 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. 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. 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.

Serum TSH and the response to radioiodine treatment of toxic multinodular goitre.

A retrospective analysis of data from 73 consecutive patients with toxic multinodular goitre treated with iodine-131 (131I) during a 2-year period was performed to investigate if serum TSH at the time of 131I treatment influences the outcome. The dose of 131I was calculated according to a model compensating for thyroid size estimated by palpation and 24-h 131I uptake. Serum TSH was determined by a third-generation assay with a functional sensitivity of 0.03 mU/l. A significantly more pronounced response to 131I treatment was observed in patients with TSH > 0.0 mU/l than in patients with TSH = 0.0 mU/l (P = 0.0006. This difference resulted in a threefold lower frequency of non-responders and a fivefold higher rate of early hypothyroidism in the group with detectable serum TSH. While the high frequency of hypothyroidism among patients with measurable serum TSH can be explained by destruction of normal thyroid tissue, the high frequency of treatment failure in the group with serum TSH = 0.0 mU/l suggests that autonomous thyroid tissue may also be sensitized to a deleterious effect of 131I through stimulation by TSH. We conclude that serum TSH has a significant influence on the outcome of 131I treatment of toxic multinodular goitre. The results of 131I treatment may be improved by adjustment of the dose of 131I according to the serum TSH level, in addition to adjustment for goitre size and 24-h 131I uptake.

Tumors after radiotherapy for thyroid cancer. A case-control study within a cohort of thyroid cancer patients.

A case-control study of Swedish thyroid cancer patients was conducted to evaluate the possible influence of 131I treatment and external radiotherapy on the risk of developing a subsequent cancer. Both cases and controls derived from a cohort of Swedish thyroid cancer patients treated with 131I (n = 834) or by other means (n = 1,121). Thirty-six breast, 13 stomach, 12 kidney, and 5 bladder cancers were found more than 2 years after 131I treatment/thyroid cancer diagnosis. Individual, absorbed dose in the organs was calculated by using ICRP tables, administered activity of 131I, and 24-h 131I uptake. In studying the effect of 131I and external radiotherapy no statistically significant dose-response relationships were found for cancers of the breast, stomach, bladder or kidney. When the absorbed dose from 131I was analyzed separately the risks remained essentially the same. The present follow-up time and the relatively low absorbed dose that the patients received from 131I and external radiotherapy necessitate studies with a longer follow-up time or a larger patient material before more firm conclusions can be made.

The role of thyroid scanning in hyperthyroidism.

Radionuclide thyroid imaging was performed in 872 consecutive patients with hyperthyroidism. Of these, 84% were found to have diffuse toxic hyperplasia (Graves' disease), while 12% had autonomously functioning nodules (Plummer's disease), 3% had Graves' disease developing in a multinodular gland, and in the remaining 1%, either a clear diagnosis could not be established or the hyperthyroidism was due to thyroiditis or the Jod-Basedow phenomenon. It was found that a thyroid scan seldom provides additional diagnostic information in patients with Graves' disease when a diffuse goitre is present. However, if patients are to be treated with radioiodine (131I), thyroid imaging with tracer quantitation can replace a 24-h 131I uptake measurement, this having the advantages that the patients are required to attend only once, and that the gland size can be measured. In addition, visual confirmation of tracer uptake by the thyroid is obtained and patients with thyroiditis will not receive inappropriate therapy. When single or multiple thyroid nodules are palpated, a thyroid scan is crucial in establishing an accurate diagnosis, as it is not otherwise possible to differentiate between Plummer's disease and Graves' disease developing in a multinodular gland. Indeed, in 20 of our 63 patients (32%) with single autonomously functioning nodules, the initial clinical assessment had been incorrect.

Radioiodine therapy for Graves' disease: multivariate analysis of pretreatment parameters and early outcome.

Twenty-one clinical, biochemical, scan and tracer-kinetic parameters were documented in 76 patients with Graves' disease who had received a standard 5-mCi therapy dose of 131I. Linear discriminant analysis was then undertaken to determine what combination of variables best predicted outcome. One year after therapy, 40 patients were euthyroid, 11 were hypothyroid, and 25 were still thyrotoxic. Linear discriminate functions combining 24-h 131I uptake, the presence or absence of thyroid eye signs and a computer-derived measurement of thyroid cell mass best discriminated the three outcome groups. The proportion of patients correctly reclassified according to outcome using these functions was, however, only just over 50%. It is concluded that no single or combination of pretreatment variables predicts early outcome with sufficient confidence to justify a rigorously 'scientific' approach to the administration of 131I therapy for Graves' disease.

Effects of oral thyrotropin-releasing hormone, exogenous thyroid-stimulating hormone, and withdrawal of triiodothyronine on 131I uptake after subtotal thyroidectomy.

To characterize the effects of oral TRH, exogenous TSH, and length of time of T3 withdrawal on I3II uptake, 16 patients who had undergone subtotal thyroidectomy for differentiated thyroid cancer were administered T3 (75-100 μg/day) for 8–15 weeks before 131I remnant ablation. T3 was withdrawn for 10 days in 8 patients (group 1) and for 24 days in 8 patients (group 2) before a baseline 24-h 131I uptake (study day 2), with repeat uptakes (study days 5 and 7) after the sequential administration of oral TRH (80 mg 3 times a day for 3 days) and after bovine TSH (10 U im each day for 2 days). Baseline serum TSH values were 30 ± 8 μU/ml in group 1 and 73 ± 14 in group 2 (P < 0.02), and the values did not increase at the end of the study (day 7; 36 ± 9 and 77 ± 12, respectively). Four hours after doses 1 and 7 of oral TRH, changes in serum TSH values were 10 ± 4 and 9 ± 2 in group 1, respectively, and 17 ± 6 and 10 ± 3 in group 2, respectively. The 131I uptake increased 2.8 ± 0.7% after oral TRH in group 1 (an in...

Different sensitivity of 131I uptake and TRH test during thyroxine treatment of nontoxic goiter.

Three groups of patients with nontoxic goiter were treated with T4 and studied serially. The first group (54 cases) was treated with 50 μg/day for the first month, 100 μ/day for the second, 150 μg/day for the third, and 200 μg/day for the fourth. The 4- and 24-h thyroidal 131I uptake, serum T4, resin T3 uptake, and serum TSH before and 30 min after the iv injection of 200 μg TRH were measured before and after each treatment period. The TRH response was suppressed with smaller doses of T4 than the 131I uptake. Using as the criterion for TSH suppression a completely absent TRH response and as the criterion for 131I suppression a 24-h 131I uptake of ≦5% of the administered dose, the proportion of patients showing a suppression by the TRH and the 131I tests respectively, were: with 50 μg/day, 28.5% for TRH and 0% for 131I uptake; with 100 μg/day, 70% for TRH and 7.5% for 131I uptake; with 150 μg/day, 87.5% for TRH and 22.5% for 131I uptake; and with 200 μg/day, 100% for TRH and 54.2% for 131I uptake. All diff...