Pernille Vejbjerg

Iodine intake before and after mandatory iodization in Denmark: results from the Danish Investigation of Iodine Intake and Thyroid Diseases (DanThyr) study

Iodine deficiency is still common in some European countries. In Denmark an iodine fortification programme was introduced in 1998 and a monitoring programme was established prior to iodization. This study reports the change in urinary iodine excretion caused by fortification and investigates determinants of iodine intake after fortification. Iodine excretion in casual urine samples was assessed in 4649 subjects in 1997-8 and in 3570 comparable subjects in 2004-5 in women 18-22, 25-30, 40-45 and 60-65 years of age and in men 60-65 years of age living in Aalborg (western part of Denmark) or Copenhagen (eastern part of Denmark). These areas had moderate and mild iodine deficiency, respectively, before iodine fortification. All subjects filled in a FFQ and a questionnaire regarding lifestyle factors. Iodine excretion, expressed as the estimated 24 h urinary iodine excretion and as urinary iodine concentration, increased significantly in all age and sex groups. However, the iodine intake was still below the recommended in the youngest age groups in both cities and in women 40-45 years of age living in Aalborg. Intake of milk and salt had strong significant direct associations with iodine excretion (P < 0.001). It is concluded that although the median iodine intake in the whole study population is at the recommended level, some groups still have an intake below the recommended. It is important to have a moderate milk intake to obtain a sufficient iodine intake in Denmark.

A cautious iodization programme bringing iodine intake to a low recommended level is associated with an increase in the prevalence of thyroid autoantibodies in the population

Autoantibodies against the thyroid gland with thyroid peroxidase antibody (TPO‐Ab) and thyroglobulin antibody (Tg‐Ab) as the most common can often be demonstrated in serum. The effect of public iodization programmes on antibody prevalence is uncertain.

Thyroglobulin as a marker of iodine nutrition status in the general population

OBJECTIVE The iodine status of a population is traditionally evaluated by either urinary iodine (UI) excretion or by some measure of thyroid volume and the prevalence of goitre. In this prospective study of a mandatory iodization programme, we aimed to evaluate serum thyroglobulin (Tg) as a marker of iodine status in the population. METHODS Two identical cross-sectional studies were performed before (1997-1998, n=4649) and after (2004-2005, n=3570) the initiation of the Danish iodization programme in two areas with mild and moderate iodine deficiency. Serum Tg was measured from blood samples. Thyroid volume was measured by ultrasonography. RESULTS Before iodization, the median serum Tg was considerably higher in moderate than in mild iodine deficiency. Iodization led to a lower serum Tg in all examined age groups. The marked pre-iodization difference in Tg level between the regions was eliminated. The prevalence of Tg above the suggested reference limit (40 microg/l) decreased from 11.3 to 3.7% (P<0.0001). Using bootstrapping, we demonstrated a higher efficacy of Tg than of thyroid volume to show a difference between pre- and post-iodization values. CONCLUSION We found serum Tg to be a suitable marker of iodine nutrition status in the population. The results may suggest that the Danish iodization programme has led to a sufficient iodine intake, even if the median UI excretion is still marginally low according to WHO criteria.

Lower prevalence of mild hyperthyroidism related to a higher iodine intake in the population: prospective study of a mandatory iodization programme

Objective  Marked differences in pattern of thyroid dysfunction are seen in populations with different iodine intakes. We evaluated the influence of a higher iodine intake on thyroid hormone levels and the prevalence of thyroid dysfunction in the Danish population.

Serum selenium and selenoprotein P status in adult Danes - 8-year followup.

Selenium is an essential micronutrient important to human health. The main objective of this study is to describe serum selenium and selenoprotein P status in two samples of the Danish population. In addition, the influence of various factors potentially associated with selenium status was investigated. Blood samples from a total of 817 randomly selected subjects from two cities in Denmark were analyzed. Half of the samples were collected in 1997-1998 and the other half in 2004-2005. Samples from women aged 18-22, 40-45 and 60-65 years, and men aged 60-65 years were selected for this study. All subjects had filled in a food frequency questionnaire (FFQ) and a questionnaire with information about smoking habits, alcohol consumption and exercise habits. Mean serum selenium level was 98.7+/-19.8microg/L and median selenoprotein P level was 2.72 (2.18-3.49)mg/L. Serum selenium and selenoprotein P increased with age, and selenoprotein P was higher in men than in women. Serum selenium levels decreased by 5% on average from 1997-98 to 2004-05 (P<0.001), whereas selenoprotein P level increased (P<0.001). The intake of fish correlated weakly with serum selenium level (r=0.14, P<0.001) but not with selenoprotein P level. Smoking status, alcohol intake, exercise habits, BMI and medicine use did not influence selenium status. It is concluded that selenium status in this Danish population is at an acceptable level. No major groups with regard to age, sex or lifestyle factors could be identified as being in risk for selenium deficiency.

Surveillance of Thyroid Disorders and Iodine Intake in the Danish Population before and after Mandatory Iodide Fortification of Salt: The DanThyr Program

Until recently, Denmark was considered free of iodine deficiency disorders. It had been demonstrated that urinary iodine excretion was low, with geographical variation now caused by differences in groundwater iodine content. However, goiter was not a clinical problem in children, and a national survey of more than 350000 schoolchildren did not support the necessity of an iodine fortification program. When focus turned to other parts of the population, the consequences of iodine deficiency was clear: multinodular goiter with a high occurrence of clinical and subclinical hyperthyroidism was extraordinarily common in the elderly, and pregnant women showed signs of insufficient thyroid hormone production in late pregnancy. Mild-to-moderate ID in a well-nourished population leads to a frequent occurrence of goiter and hyperthyroidism in the elderly. There may be impairment of thyroid function in pregnant women. A mandatory iodization of household salt and bread salt has led to a well-distributed increase in iodine intake in the Danish population. The Danish iodization program has led to a decrease in thyroid size and frequency of thyroid enlargement in practically all groups investigated. Iodine intake of a population should be monitored and the use of iodine-containing substances in farming and the food industry should be regulated. A program targeted to increase daily iodine intake by around 50 μg was started by the National Food Agency. The DanThyr monitoring program has shown that the populations iodine intake has increased much as planned by adding iodine (13 ppm) to table salt and bread salt. Thyroid size and the occurrence of thyroid enlargement have diminished in all age groups. There has been a small increase in the incidence of overt hyperthyroidism, which is expected to be transient.

Surveillance of Thyroid Disorders and Iodine Intake in the Danish Population before and after Mandatory Iodide Fortification of Salt

Until recently, Denmark was considered free of iodine deficiency disorders. It had been demonstrated that urinary iodine excretion was low, with geographical variation now caused by differences in groundwater iodine content. However, goiter was not a clinical problem in children, and a national survey of more than 350000 schoolchildren did not support the necessity of an iodine fortification program. When focus turned to other parts of the population, the consequences of iodine deficiency was clear: multinodular goiter with a high occurrence of clinical and subclinical hyperthyroidism was extraordinarily common in the elderly, and pregnant women showed signs of insufficient thyroid hormone production in late pregnancy. Mild-to-moderate ID in a well-nourished population leads to a frequent occurrence of goiter and hyperthyroidism in the elderly. There may be impairment of thyroid function in pregnant women. A mandatory iodization of household salt and bread salt has led to a well-distributed increase in iodine intake in the Danish population. The Danish iodization program has led to a decrease in thyroid size and frequency of thyroid enlargement in practically all groups investigated. Iodine intake of a population should be monitored and the use of iodine-containing substances in farming and the food industry should be regulated. A program targeted to increase daily iodine intake by around 50 μg was started by the National Food Agency. The DanThyr monitoring program has shown that the populations iodine intake has increased much as planned by adding iodine (13 ppm) to table salt and bread salt. Thyroid size and the occurrence of thyroid enlargement have diminished in all age groups. There has been a small increase in the incidence of overt hyperthyroidism, which is expected to be transient.