Original Article
European Journal of Clinical Nutrition (2006) 60, 210–213. doi:10.1038/sj.ejcn.1602290; published online 26 October 2005
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
Guarantor: M Milakovic.
Contributors: MM collected data from the uptake measurements and compared the data with previous studies, GB was responsible for the nuclear medicine investigations and radiation aspects, RE was responsible for the establishment of the Mölnlycke population studies and mainly responsible for the contact with participants and, EN was responsible for endocrine and statistical aspects of the study. All authors contributed to the analysis and interpretation of data, and the preparation of the manuscript.
M Milakovic1, G Berg2, R Eggertsen1 and E Nyström3
- 1Mölnlycke Primary Health Care and Research Centre, Department of Primary Health Care, Sahlgrenska Academy at Göteborg University, Göteborg, Sweden
- 2Sahlgrenska University Hospital, Department of Oncology, Sahlgrenska Academy at Göteborg university, Göteborg, Sweden
- 3Sahlgrenska University Hospital, Department of Medicine, Sahlgrenska Academy at Göteborg University, Göteborg, Sweden
Correspondence: Dr G Berg, Department of Oncology, Sahlgrenska University Hospital, S-413 45 Göteborg, Sweden. E-mail: gertrud.berg@oncology.gu.se
Received 24 November 2004; Revised 11 July 2005; Accepted 2 August 2005; Published online 26 October 2005.
Abstract
Background:
In Sweden, iodine has been added to table salt (10 mg/kg) since 1936; this amount was increased in 1966 to 50 mg/kg.
Objective:
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 (24h IU) and thyroid nodularity (thyroid scintigraphy). To compare the euthyroid 24h IU with uptake of thyrotoxic individuals, and with observations from 1955.
Methods:
The 24h IU was used in euthyroid individuals after oral administration of 0.1 MBq/2.7 
Ci radioiodine and imaging of the thyroid gland was carried out using 99mTc-pertechnetate.
Results:
In 1999–2000, the mean 24h 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 24h IU was 61% (range 29–89%). In 1955, the 24h 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%).
Conclusions:
The population sample studied had to be small for ethical reasons. We conclude that the reference interval for 24h 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.
Keywords:
iodine supplementation, radioiodine uptake, scintigraphy
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