Inge Bülow

Goitre prevalence and thyroid abnormalities at ultrasonography : a comparative epidemiological study in two regions with slightly different iodine status

The association between severe iodine deficiency and endemic goitre is well established, but little information is available on the relation between milder degrees of iodine deficiency and goitre prevalence.

Dietary iodine intake and urinary iodine excretion in a Danish population: effect of geography, supplements and food choice

I deficiency diseases remain a health problem even in some developed countries. Therefore, measurement of I intake and knowledge about food choice related to I intake is important. We examined I intake in 4649 randomly selected participants from two cities in Denmark (Copenhagen and Aalborg) with an expected difference in I intake. I intake was assessed both by a food frequency questionnaire and by measuring I in casual urine samples. I excretion was expressed as a concentration and as estimated 24-h l excretion. Further, subgroups with low I intake were recognized. I intake was lower in Aalborg than in Copenhagen for all expressions, and lower than recommended in both cities if I intake from supplements was not included. Milk was the most important I source, accounting for about 44% of the I intake, and milk (P<0.001) and fish (P=0.009) intake was related to I excretion in a multiple linear regression model. Thus, risk groups for low I intake were individuals with a low milk intake, those with a low intake of fish and milk, those not taking I supplements and those living in Aalborg where the I content in drinking water is lower. Even individuals who followed the advice regarding intake of 200-300 g fish/week and 0.5 litres milk/d had an intake below the recommended level if living in Aalborg.

Risk Factors for Goiter and Thyroid Nodules

The occurrence of thyroid diseases is determined by interplay between genetic and environmental factors. The major environmental factor that determines goiter prevalence is iodine status, but other environmental factors influencing entire populations have been identified such as goitrogens in food and drinking water. Less focus has been on individual environmental factors and the interplay between factors. The goiter prevalence is higher in certain groups in the population. The variation in goiter prevalence between the genders is well known with a higher occurrence among women. The association with age is probably dependent on iodine status, because it seems that the zenith of goiter prevalence appears earlier in life the more severe iodine deficiency the population is exposed to. The association with individual risk factors has been investigated in some studies, especially the association with tobacco smoking. In iodine-deficient areas, a strong association between tobacco smoking and goiter prevalence is found, whereas the association is less pronounced in iodine-replete areas. This was predictable from experimental studies showing thiocyanate to be the mediator of the goitrogenic effect of tobacco smoke acting as a competitive inhibitor of iodine uptake. The association with alcohol intake has only been investigated in few studies, but a low occurrence of goiter among alcohol consumers has been found. The mechanism of this association is not known. Increased goiter prevalence during pregnancy has been reported, and recently a long-term goitrogenic effect of pregnancies has also been shown. As demonstrated for tobacco smoking, this association is dependent on iodine status, because the association has only been found in areas with a suboptimal iodine intake. This indicates pregnancy-induced goiter to be the result of exacerbation of existing iodine deficiency. Recently, the use of oral contraceptives has been shown to be associated with a markedly reduced prevalence of goiter, although experimental studies have previously shown proliferative effects of estrogens on thyrocytes. Some implications for prevention of thyroid disease could be suggested. Discussion of smoking habits should be included in a consultation for goiter with a motivation to quit smoking. Iodine deficiency has particularly strong goitrogenic effects during pregnancy and for the sake of the mother as well as the fetus, sufficient iodine supply should be ensured to all pregnant women. The difference in age maximum in goiter prevalence suggests that monitoring of iodine deficiency disorders should ideally include a spectrum of age groups.

Alcohol consumption is associated with reduced prevalence of goitre and solitary thyroid nodules

OBJECTIVE Goitre prevalence is dependent on iodine intake and smoking habits, but further risk factors have only been examined briefly. We examined the association between alcohol consumption and the prevalence of thyroid enlargement and nodularity.

Evaluation of a semi-quantitative food frequency questionnaire to estimate iodine intake

Objective: To evaluate a food frequency questionnaire (FFQ) used to assess the dietary intake of iodine.Design: The iodine intake determined by the FFQ was compared with 4-day dietary records and with iodine excretion in 24 h urine samples in a subgroup of participants in a cross-sectional study of iodine intake and thyroid diseases in Denmark. Furthermore, the intake of fish determined from the FFQ was compared with the intake of fish from a simple record kept for 3 months.Subjects: Women aged 25–30 y and 60–65 y.Results: Median iodine intake was similar when determined from the FFQ and from dietary records and the correlation between these measures was 0.52 (P<0.001). Iodine intake was higher than iodine excretion (P<0.001). The cross-check questions in the FFQ (for example the question ‘How often did you get any kind of fish?’) underestimated the intake. In contrast, the intake of a specific fish tended to be overestimated by the FFQ when compared with the 3 month record of fish intake.Conclusion: The FFQ can be used to classify subjects into low and high iodine intake groups, but the level of iodine tends to be overestimated.Sponsorship: The Danish Medical Foundation and the 1991 Pharmacy Foundation.European Journal of Clinical Nutrition (2001) 55, 287–292

Low socio-economic status and familial occurrence of goitre are associated with a high prevalence of goitre

The occurrence of goitre is dependent on genetic and environmental factors, but the associations with socio-economic and life-style factors have only been examined briefly. A cohort of 4649 participants from the general population was examined with questionnaires, thyroid ultrasonography, clinical examination and blood tests. Data were analysed in linear models and logistic regression analysis. Thyroid volume and serum thyroglobulin were closely associated with educational level with higher values in the group with the lowest levels of education (p < 0.001). The same pattern applied to thyroid multinodularity at ultrasonography (p = 0.002) and palpable goitre (p = 0.01). Physical activity in leisure time was negatively associated with thyroid enlargement (p = 0.02) and serum thyroglobulin (p < 0.001). These associations diminished markedly if adjustment was made for smoking habits, alcohol consumption and iodine intake. Familial occurrence of goitre was associated with goitre prevalence (Odds Ratio 2.5, 95% CI: 1.6–3.9), but did not confound the socio-economic associations. In conclusion, social imbalances in the occurrence of goitre were identified. These imbalances could in part be explained by differences in smoking habits and iodine intake.