Gertrud Berg

Leukaemia incidence after iodine-131 exposure

Leukaemia is one of the most prominent late effects of exposure to ionising radiation. We have studied the incidence of leukaemia among 46,988 Swedish patients exposed to iodine-131 (131I) for diagnostic reasons or to treat hyperthyroidism or thyroid cancer. The observed number of leukaemias was compared with that expected based on incidence data from the general population. The mean absorbed dose to the bone marrow was estimated as 14 mGy (range 0.01-2.226). 195 leukaemias occurred more than 2 years after exposure, and the standardised incidence ratio (SIR) was 1.09 (95% confidence interval 0.94-1.25). Similar, but again not significantly, increased risks were seen for chronic lymphocytic leukaemia (CLL) (SIR = 1.08), a malignant condition not found to be increased after irradiation, and for non-CLL (SIR = 1.09). The risk of leukaemia did not vary by sex, age, time, or radiation dose from 131I. One reason for the absence of a radiation effect, other than chance, includes the possible lowering of risk when exposure is protracted over time as occurs with 131I. Excess leukaemia risks of more than 25% could thus be excluded with high assurance in this population of mainly adults. These results should be reassuring to patients exposed to 131I in medical practice and to most individuals exposed to the fall-out from the Chernobyl accident.

Radioiodine ablation and therapy in differentiated thyroid cancer under stimulation with recombinant human thyroid-stimulating hormone

We investigated whether recombinant human TSH (rhTSH) safely and effectively induces uptake of high-dose 131-iodine (131I) to ablate thyroid remnant or treat disease, in patients with well-differentiated thyroid carcinoma. Eleven consecutive patients unable to tolerate thyroid hormone withdrawal received one im injection of 0.9 mg rhTSH on 2 consecutive days before receiving 4000 MBq (~108 mCi) radioiodine orally. Eight patients received one, and 3 patients 2 courses. Our series comprised 7 women and 4 men (mean age, 78 yr, range: 56–87 yr). Ten patients had undergone total or near-total thyroid-ectomy up to 19 yr earlier. rhTSH-stimulated single course radioiodine with the intention to ablate thyroid remnant was performed in 3 patients, with following estimation of radioiodine uptake and TG measurements. Of another 8 patients given this treatment palliatively, 5 had radiological, clinical and/or laboratory response, including: 80% decreased pathological uptake between treatment courses; pronounced decrease in bone pain; diminished symptoms; improved physical condition and quality of life; lower serum TG concentration; and/or normalization of TG recovery test. Two patients with small lung metastases on computed tomography had no detectable radioiodine uptake or other response; they also lacked uptake after withdrawal-stimulated radioiodine treatment. Despite being elderly and frail, patients generally tolerated treatment well; rhTSH caused nausea in one patient and transiently increased pain in bone and soft tissue lesions in another. We conclude that rhTSH-stimulated high-dose radioiodine for remnant ablation or tumor treatment is safe, feasible and seemingly effective, enhancing quality of life and offering reasonable palliation in patients with advanced disease.

Clinical outcome of radioiodine treatment of hyperthyroidism: a follow‐up study

Objectives. To study the clinical outcome of treatment of hyperthyroid patients with radioiodine.

Determination of intrathyroidal iodine by X-ray fluorescence analysis in 60- to 65-year olds living in an iodine-sufficient area.

Objectives.  X‐ray fluorescence (XRF) is a non‐invasive method for determining the iodine content of the thyroid gland in vivo. In spite of the obvious clinical value of such a method in situations of iodine deficiency or iodine overload, the method has not so far been widely used. The objective was to investigate the applicability of the XRF method in a larger number of subjects.

Incidence rate and clinical features of hyperthyroidism in a long‐term iodine sufficient area of Sweden (Gothenburg) 2003–2005

To study hyperthyroidism in long‐term iodine sufficiency (IS), as iodine supply affects its occurrence.

Urinary iodine and thyroid volume in a Swedish population

Objective.  To evaluate the present efficacy of an iodine supplementation programme working in Sweden since 1936 by studying the iodine excretion in urine and determining the thyroid volume in a population in a semi‐rural community.

Adequate iodine nutrition in Sweden: a cross-sectional national study of urinary iodine concentration in school-age children

Background/Objectives:Sweden has a long-standing salt iodization program; however, its effects on iodine intake have never been monitored on a national level. The objective of this study was to evaluate iodine nutrition in the Swedish population by measuring the urinary iodine concentration (UIC) in a national sample of Swedish school-age (6–12 years of age) children.Subjects/Methods:A stratified probability proportionate to size cluster sampling method was used to obtain a representative national sample of school-age children from 30 clusters. Spot urine samples were collected for UIC analysis using a modified Sandell–Kolthoff method.Results:The median UIC of the children (n=857) was 125 μg/l (range 11–757 μg/l). The proportion of children with a UIC <100 μg/l was 30.0% and the proportion of children with a UIC <50 and >300 μg/l was 5.5 and 3.0%, respectively.Conclusions:The iodine nutritional status of the Swedish population is adequate. Iodized table salt remains the main dietary source of iodine in Swedish diet. Recommendations to reduce total salt intake in the population urge increased use of iodized salt in the production of processed foods. Pregnant and lactating women with high iodine requirements may still be at risk for low iodine intake. This study will serve as the basis for future monitoring of iodine nutritional status in Sweden.

Thyroid volume in Swedish school children: a national, stratified, population-based survey

Background/Objectives:Sweden has had a salt iodination program since 1936. This first national surveillance study on iodine nutrition infers an adequate level of urinary iodine concentration (UIC 125 μg/l) and the aim is now to evaluate thyroid volume (Tvol) in the same national sample.Subjects/Methods:A stratified probability proportionate to size cluster sampling was used to obtain a representative national sample of Swedish children aged 6–12 years. Median Tvol obtained ultrasonographically and the prevalence of enlarged thyroid glands were compared with an international reference standard. Regional differences were evaluated through comparisons of Tvol between coastal and inland areas, urban and rural regions, and former goitre and non-goitre regions.Results:Tvol was correlated with age, body surface area (BSA), weight, height and body mass index for both sexes (P<0.0001) but not with UIC. The most important predictors for Tvol were age (girls: P<0.0001, boys: P=0.001) and BSA (girls: P<0.0001, boys: P<0.01). Median Tvol was higher in Sweden than in the reference study (P<0.0001). The prevalence of goitre was higher in Sweden (correlated to age 22.3%, BSA 15.7%, weight 17.6%, height 12.9%) than in the international reference (correlated to age 2.5%, BSA 2.5%, weight 2.5%, height 2.5%) (P<0.0001). Thyroids were larger in boys from urban and former non-goitre areas.Conclusions:Tvols were higher in Swedish school children than in the international reference study although iodine intake is considered optimal in Sweden. These findings underline the importance of regular monitoring of iodine intake, especially with regard to the decreased intake of table salt that is likely to follow initiation of health campaigns.

Consequences of inadvertent radioiodine treatment of Graves' disease and thyroid cancer in undiagnosed pregnancy. Can we rely on routine pregnancy testing?

Introduction. Radioiodine and most cytostatic treatments are contraindicated in pregnancy. Still, inadvertent therapy does occur. Radioiodine was given to two pregnant women with Graves’ disease and thyroid cancer respectively, both in their 20th gestational week. Routine pregnancy tests based on urinary β-hCG had failed to indicate pregnancy in both cases. Methods. Estimation of doses to the foetuses and foetal thyroids. Scrutiny of pregnancy testing. Results and Conclusions. Doses to foetal thyroids were ablative (250–600 Gy). Total foetal dose in the Graves’ patient was 100 mGy and compatible with survival, whereas a foetal dose of approximately 700 mGy together with induced hypothyroidism was fatal for the foetus of the cancer patient. Routine pregnancy tests may fail early and late in pregnancy. The possibility of pregnancy should be considered in all fertile women before therapy with radionuclides or cytostatic regimens, and a clinical investigation undertaken on wide indications with determination of serum β-hCG, preferably together with an ultrasound examination.

Screening for thyroid disease of 15-17-year-old schoolchildren in an area with normal iodine intake.

Abstract. Milakovic M, Berg G, Eggersten R, Lindstedt G, Nyström E (Sahlgrenska University Hospital, Göteborg, Sweden). Screening for thyroid disease of 15–17‐year‐old schoolchildren in an area with normal iodine intake. J Intern Med 2001; 250: 208–212.