Iodine. Do We Need an Enrichment Program in Denmark?

Rasmussen, Lone Banke; Andersson, Grethe; Haraldsdóttir, Jóhanna; Kristiansen, Eva; Mølsted, Kirsten; Laurberg, Peter; Overvad, Kim; Perrild, Hans; Ovesen, Lars

doi:10.3109/09637489609006950

Cited by 32 publications

(26 citation statements)

References 7 publications

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“…This is in accord with the prevalences of hyperthyroidism and hypothyroidism previously described (18). Being aware of the risk of increasing the prevalence of hypothyroidism to the higher level found in iodinereplete areas, there seems to be evidence for a possible beneficial effect of increasing the iodine intake of this population, and the authorities have just recently initiated an iodine supplement programme (28).…”

Section: Discussionsupporting

confidence: 58%

Thyroid structure and size and two-year follow-up of solitary cold thyroid nodules in an unselected population with borderline iodine deficiency

Knudsen

Perrild²,

Christiansen

et al. 2000

European Journal of Endocrinology

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Objective: Multinodular goitre has been found with a high prevalence in iodine-deficient areas, but less frequently in iodine-replete areas; the iodine intake sufficient to prevent goitre has not been established, however. Methods: We report data from an ultrasonic investigation of the thyroid glands of 2656 randomly selected subjects aged 41 to 71 years in an area with borderline iodine deficiency. Results: Median iodine concentration in spot urine samples was 70 mg/l. Multinodular thyroid structure was found in 23% of the population, increasing in women from 20 to 46% with increasing age, and in men from 7 to 23%. Solitary, scintigraphically cold, thyroid nodules >10 mm were found in 2.4% of the population with the same prevalence in the different age and sex groups. Two years of follow-up of these cold nodules revealed no signs of malignancies. Median thyroid volume was 11.0 ml. Thyroid enlargement (>18 ml for women and >25 ml for men) was found among 13.1% of the women and 6.2% of the men, and the prevalence increased with age. The presence of thyroid nodules was related to positive anti-thyroperoxidase antibody (TPO Ab) titres, whereas thyroid enlargement was associated with iodine excretion <50 mg/day. Conclusions: Thyroid enlargement was associated with low iodine excretion and median thyroid volume was slightly increased compared with iodine-replete areas. Multinodular thyroid structure was found with a high prevalence and was associated with TPO Ab >200 kU/l. Cold thyroid nodules were moderately prevalent, with no cases of detected malignancies during 2 years of follow-up.

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Section: Discussionsupporting

confidence: 58%

Thyroid structure and size and two-year follow-up of solitary cold thyroid nodules in an unselected population with borderline iodine deficiency

Knudsen

Perrild²,

Christiansen

et al. 2000

European Journal of Endocrinology

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“…The difference in average body weight between the group with slightly elevated TSH (median 4.5 mU/l) and slightly low TSH (median 0.28 mU/l) (all had normal free T 4 and free T 3 ) was 5.5 kg, and the group with elevated TSH was on average 4.0 kg heavier than the group with a TSH of 1-1.99 mU/l. Serum-free T 4 showed a negative association with BMI, which demonstrates that the elevated TSH is caused by thyroid failure and not by a central effect such as leptin stimulation of hypothalamic thyrotropin-releasing hormone secretion. The findings, which have been confirmed in a Norwegian population study (33) illustrate that even small differences in thyroid function in a population may have clearly detectable effects on other variables in the population.…”

Section: Thyroid Function and Overweight In The Populationmentioning

confidence: 96%

“…In Denmark, the low iodine intake was associated with signs of insufficient thyroid hormone production in pregnant women, who showed an increase in serum thyroid-stimulating hormone (TSH) in late pregnancy (3), and a very frequent occurrence of goiter and hyperthyroidism in elderly people caused by autonomous thyroid nodules (4). To rectify this deficiency of iodine, the Danish Food and Veterinary Administration introduced a voluntary program of universal salt iodization.…”

mentioning

confidence: 99%

The Danish investigation on iodine intake and thyroid disease, DanThyr: status and perspectives

et al. 2006

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Objective: Denmark was an area of iodine deficiency, and mandatory iodine fortification of table salt and salt in bread (13 p.p.m. iodine) was initiated in 2000/2001. The Danish investigation on iodine intake and thyroid disease (DanThyr) is the monitoring of the iodine fortification program. Design and methods: DanThyr consists of three main parts: a study of population cohorts initialized before (nZ4649) and after (nZ3570) iodization of salt, a prospective identification of incident cases of overt hyper-and hypothyroidism in a population of around 550 000 people since 1997, and compilation of data from the national registers on the use of thyroid medication, thyroid surgery, and radioiodine therapy. Studies were carried-out in parallel in subcohorts living in areas with differences in iodine content of ground water. Results: The study showed profound effects of even small differences in iodine intake level on the prevalence of goiter, nodules, and thyroid dysfunction. Mild and moderate iodine deficiency was associated with a decrease in serum TSH with age. Other environmental factors were also important for goiter development (increase in risk, smoking and pregnancy; decrease in risk, oral contraception and alcohol consumption), and the individual risk depended on the genetic background. Environmental factors had only a minor influence on the prevalence of thyroid autoantibodies in the population. There were more cases of overt hypothyroidism in mild than in moderate iodine deficiency caused by a 53% higher incidence of spontaneous (presumably autoimmune) hypothyroidism. On the other hand, there were 49% more cases of overt hyperthyroidism in the area with moderate iodine deficiency. The cautious iodine fortification program, aiming at an average increase in iodine intake of 50 mg/day has been associated with a 50% increase in incidence of hyperthyroidism in the area with the most severe iodine deficiency. The incidence is expected to decrease in the future, but there may be more cases of Graves' hyperthyroidism in young people. Conclusion: A number of environmental factors influence the epidemiology of thyroid disorders, and even relatively small abnormalities and differences in the level of iodine intake of a population have profound effects on the occurrence of thyroid abnormalities. Monitoring and adjustment of iodine intake in the population is an important part of preventive medicine.European Journal of Endocrinology 155 219-228

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“…This study was part of The Danish Investigation of Iodine Intake and Thyroid Diseases (DanThyr), which monitors the Danish iodine fortification programme (16,17). The DanThyr programme includes a number of studies among which is a prospective study of the incidence of overt thyroid dysfunction in an open population cohort before the iodine fortification of salt.…”

Section: Methodsmentioning

confidence: 99%

Epidemiology of subtypes of hypothyroidism in Denmark

et al. 2006

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Objective: Studies of hypothyroidism are often based on referred patients, and limited information is available on the incidence rates of subtypes of hypothyroidism in the general population. We therefore studied incidences of subtypes of primary, overt hypothyroidism in a Danish population cohort and compared incidences in two subcohorts with different levels of iodine intake. Design: A prospective population-based study, monitoring a well-defined cohort representative of the Danish population. Methods: The Danish Investigation of Iodine Intake and Thyroid Diseases registry of hyper-and hypothyroidism was established as part of the monitoring of the iodine fortification of salt in Denmark. A computer-based system linked to laboratory databases identified all patients diagnosed with new, biochemically overt hypothyroidism in populations living in Aalborg (moderate iodine deficiency, n ¼ 311 102) and Copenhagen (mild iodine deficiency, n ¼ 227 632). We subsequently evaluated all identified patients to verify incident thyroid disease, and subclassified hypothyroidism into nosological types. Results: During a 4-year period (2 027 208 person-years) 685 new cases of overt hypothyroidism were diagnosed in the cohort; the incidence rate was 32.8 per 100 000 person-years (standardised to the Danish population). Nosological types of hypothyroidism were: spontaneous (presumably autoimmune) 84.4%, post-partum 4.7%, amiodarone-associated 4.0%, subacute thyroiditis 1.8%, previous radiation or surgery 1.8%, congenital 1.6% and lithium-associated 1.6%. Crude incidence rates were 29.0 around Aalborg and 40.6 in an area of Copenhagen. The higher incidence rate of hypothyroidism in the area with higher iodine intake was caused solely by more cases of spontaneous (presumably autoimmune) hypothyroidism, whereas the incidence of non-spontaneous hypothyroidism (all types combined) was significantly lower in the area with higher iodine intake. Conclusion: In a population-based study we observed a higher incidence of hypothyroidism with higher iodine intake. This was due solely to the entity of spontaneous hypothyroidism. The occurrence of overt hypothyroidism was relatively low in Denmark.European Journal of Endocrinology 154 21-28

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Iodine. Do We Need an Enrichment Program in Denmark?

Cited by 32 publications

References 7 publications

Thyroid structure and size and two-year follow-up of solitary cold thyroid nodules in an unselected population with borderline iodine deficiency

Thyroid structure and size and two-year follow-up of solitary cold thyroid nodules in an unselected population with borderline iodine deficiency

The Danish investigation on iodine intake and thyroid disease, DanThyr: status and perspectives

Epidemiology of subtypes of hypothyroidism in Denmark

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