Victories and challenges in optimizing iodine intake.
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Dietary Supplements↗
Biomedical subjects
Peter Laurberg
Publications and source records attributed to Peter Laurberg.
Iodine nutrition in breast-fed infants is impaired by maternal smoking.
Lack of iodine for thyroid hormone formation during the fetal stage and/or the first years of life may lead to developmental brain damage. During the period of breastfeeding, thyroid function of the infant depends on iodine in maternal milk. We studied healthy, pregnant women admitted for delivery and their newborn infants. Cotinine in urine and serum was used to classify mothers as smokers (n = 50) or nonsmokers (n = 90). Smoking and nonsmoking mothers had identical urinary iodine on d 5 after delivery, but smoking was associated with reduced iodine content in breast milk (smokers 26.0 micro g/liter vs. nonsmokers 53.8 micro g/liter; geometric mean, P < 0.001) and in the infants' urine (smokers 33.3 micro g/liter, vs. nonsmokers 50.4 micro g/liter, P = 0.005). Results were consistent in multivariate linear models and by logistic regression analysis. The odds ratio for smoking vs. nonsmoking mothers to have lower breast milk than urinary iodine content was 8.4 (95% confidence interval, 3.5-20.1). In smokers, iodine transfer into breast milk correlated negatively to urinary cotinine concentration. Smoking mothers had significantly higher serum levels of thiocyanate, which may competitively inhibit the sodium-iodide symporter responsible for iodide transport in the lactating mammary gland. Smoking during the period of breastfeeding increases the risk of iodine deficiency-induced brain damage in the child. Women who breastfeed should not smoke, but if they do, an extra iodine supplement should be considered.
Birth Weight↗
Patients on appropriate T(4) replacement are as content as they would be on any thyroid hormone.
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Hormone Replacement Therapy↗
Gender diversity in developing overweight over 35 years of Westernization in an Inuit hunter cohort and ethno-specific body mass index for evaluation of body-weight abnormalities.
OBJECTIVE: To establish an Inuit body mass index (BMI) norm from a healthy, not malnourished, pure Inuit population and to investigate the development of overweight in the Inuit in Greenland. DESIGN: Longitudinal study with 35 years follow-up on overweight among Inuit in Greenland. METHODS: The heights and weights of 97% of all inhabitants in Eastgreenland in 1963 (n=1852) were recovered recently and BMI calculated. We obtained similar data in 96% of the 50-69-year-old population in Eastgreenland in 1998 and in a random sample of 25% of individuals aged 50-69 years in the capital Nuuk (n=535). RESULTS: Overweight or obesity, as defined by the World Health Organization (WHO), was found in 30% of all men and 22% of all women in Eastgreenland in 1963, and in 31% of young Inuit hunters in 1963. Such high rates were incompatible with a hunter's way of living. Inuit-specific BMI norms from data on healthy Inuit aged 20-29 years in 1963 were computed: men, 20.2-27.9; women, 17.9-27.7. These differed from the WHO classification (P<0.001). Using the Inuit-specific BMI norm for the classification of 50-69-year-old Inuit in 1963 and 1998, the fraction of overweight men increased by over six times (4.0 to 25.6%; P<0.001), and overweight increased with Westernization (P=0.001). The fraction of overweight women by the Inuit BMI norm doubled from 1963 to 1998 (14.0 to 30.7%; P<0.001) while median BMI remained unaltered (P=0.22) because the fraction of slim women more than doubled (3.5 to 9.0%; P<0.001). CONCLUSION: A steep increase in the fraction of overweight Inuit men and women calls for intervention. Westernization predicted increased BMI. In women the increased number of obese people was accompanied by an increased fraction of slim people. This illustrates that transition can be modified and indicates that monitoring of populations in transition should observe gender differences. Finally, the historical data argue against the global applicability of the WHO delineation of normal BMI.
Adult↗
Body proportions in healthy adult Inuit in East Greenland in 1963.
OBJECTIVES: It is important to know the starting point when describing changes in Inuit in transition. STUDY DESIGN: The original charts of 1,852 individuals from the epidemiological investigation in East Greenland around 1963 performed by Littauer and colleagues were recovered recently. They included height, weight and a physical investigation. METHODS AND RESULTS: The focus of this paper was adult Inuit body proportions in 1963 by ten-year age groups excluding participants with disabilities affecting body build. Relatively stable values were seen in both genders with age. Median values in men/women aged 20 years and above were: height 164/153.5 cm, weight 64/54 kg and BMI 23.7/23.1. Men aged 50 years and above had a little lower height and weight than young men. Women aged 40-49 years had a higher weight and BMI, but this evened out in the older age groups. Median BMI was relatively high compared to WHO definition. CONCLUSIONS: The data from 1963 gives a starting point for evaluating changes in Inuit body build and the prevalence of overweight. Furthermore, they indicate a need for Inuit-specific normal BMI delineation.
Adult↗
Feasibility of Dual-Energy X-ray Absorptiometry in Arctic field studies.
BACKGROUND: Bone strength decreases with age. Bone mineral density (BMD) is a measure of bone strength. Data on BMD in present-day Inuit are limited, and data on circumpolar populations using Dual Energy X-ray Absorptiometry (DEXA scanning) are lacking. OBJECTIVES: Our aims were to validate DEXA scanning for use in field studies in the Arctic region and to obtain data on BMD in Greenland Inuit. METHODS: We measured BMD in 52 healthy Inuit living in Ilulissat and Saqqaq in North Greenland using a portable peripheral DEXA scanner. The measurement sites were forearms and calcaneal bones. Two measurements were performed at both radii and both calcanei. Triplicate measurements were performed in eleven Inuit. RESULTS: The portable scanner fitted into a standard bag suitable for transportation in the arctic winter. Imprecision was well within 2% for all calibrations. CV% were 0.16% to 1.79% in the forearms and 0.38% to 1.53% in the heels. The overall CV% was 1.09% in forearm and 1.01% in heel. Mean BMD in men was 0.569 g/cm2 in forearms and 0.542 in heel. In women it was 0.479 in forearms and 0.468 in heel. CONCLUSION: DEXA scanning is a feasible, reliable and comfortable method in rural Greenland. BMD values are now available for Greenland Inuit.
Absorptiometry, Photon↗
Humic substances in drinking water and the epidemiology of thyroid disease.
Thyroid diseases are common in all populations but the type and frequency depends on environmental factors. In Denmark geographical differences in iodine intake are caused by different iodine contents of drinking water, which varies from < 1 to 139 microg iodine per litre. Comparative epidemiologic studies have demonstrated considerable differences in type and occurrence of thyroid disease with more goitre and hyperthyroidism in Aalborg with water iodine content around 5 microg/L, and more hypothyroidism in Copenhagen with water iodine around 20 microg/L. In Denmark, iodine in ground water is bound in humic substances, which have probably leached from marine sediments in the aquifers. Interestingly, humic substances in water from other parts of the world have goitrogenic properties, especially humic substances from coal and shale. Humic substances are heterogeneous mixtures of naturally occurring molecules, produced by decomposition of plant and animal tissues. The effect of humic substances in drinking water on the epidemiology of thyroid disease probably depends on the source of aquifer sediments.
Chelating Agents↗
Thyroid peroxidase and thyroglobulin autoantibodies in a large survey of populations with mild and moderate iodine deficiency.
BACKGROUND AND AIMS: Autoimmune thyroiditis is one of the most common autoimmune disorders. Autoantibodies against the thyroid gland, with thyroid peroxidase antibody (TPO-Ab) and thyroglobulin antibody (Tg-Ab) as the most common autoantibodies, can often be demonstrated in serum in population surveys. In the present study we evaluated if TPO-Ab and Tg-Ab tend to develop in parallel or whether one or the other may be more prevalent in subsets of the population. METHODS: In a cross-sectional comparative study, performed in two areas of Denmark with mild and moderate iodine deficiency, 4649 randomly selected subjects in age groups between 18 and 65 years were examined. Blood tests were analysed for TPO-Ab and Tg-Ab using assays based on the radioimmunoassay (RIA) technique. The participants answered questionnaires, were clinically examined and had urine samples collected. RESULTS: The overall prevalence rate of thyroid autoantibodies (TPO-Ab and/or Tg-Ab) was 18.8%. The prevalence rates of TPO-Ab and Tg-Ab were similar (13.1 vs. 13.0%). Both antibodies were more frequent in females than in males, and in females the prevalence rates increased with age. In the age group 60-65 years thyroid antibodies were more frequently measured in sera from moderate than from mild iodine-deficient area (P = 0.02), whereas no differences were seen in younger subjects. In 38.8% of participants with thyroid autoantibodies in serum, both antibodies were present. In sera with both TPO-Ab and Tg-Ab present the concentrations of the antibodies were generally higher than in sera with only one type of antibody present. CONCLUSION: The prevalence rates of TPO-Ab and Tg-Ab were similar in this large population survey. The results suggest that TPO-Ab and Tg-Ab predominantly develop due to a general alteration in the immune system, whereas specific antigenic mechanisms are probably of less importance. However, further studies are needed to clarify the mechanisms involved in the development of thyroid autoantibodies.
Adolescent↗
Interferon-alpha and autoimmune thyroid disease.
Interferon-alpha (IFN alpha) is the main therapeutic agent in patients infected with the hepatitis C virus (HCV). It is rather safe, but is known to induce the production of autoantibodies and can lead to the occurrence of autoimmune disease. This minireview focuses on the induction of autoimmune thyroid disease (AITD) in HCV-infected patients treated with IFN alpha. Females carry a higher risk to develop AITD upon IFN alpha treatment, with a relative risk of 4.4 (95% confidence interval 3.2-5.9). The presence of thyroid peroxidase antibodies before therapy has a relative risk for AITD of 3.9 (95% confidence interval 1.9-8.1). IFN alpha-associated AITD can consist of autoimmune primary hypothyroidism, Graves' hyperthyroidism, and destructive thyroiditis, with hypothyroidism being the most common side effect. The clear association between AITD and IFN alpha use suggests that high endogenous IFN alpha levels may also be associated with naturally occurring AITD. High endogenous IFN alpha levels are seen in patients infected with certain viruses. It is concluded that IFN alpha is one of the environmental factors capable of triggering the onset of AITD in genetically susceptible individuals.
Autoantibodies↗
Biologic variation is important for interpretation of thyroid function tests.
Large variations exist in thyrotropin (TSH) and thyroid hormones in serum. The components of variation include preanalytical, analytical, and biologic variation. This is divided into between- and within-individual variation. The latter consists of circadian and seasonal differences although there are indicators of a genetically determined starting point. The ratio of within- to between-individual variation describes the reliability of population-based reference ranges. This ratio is low for serum TSH, thyroxine (T(4)) and triiodothyronine (T(3)) indicating that laboratory reference ranges are relatively insensitive to aberrations from normality in the individual. Solutions are considered but reducing the analytical variation below the calculated analytical goals of 7%, 5% and 12% for serum T(3), T(4), and TSH does not improve diagnostic performance. Neither does determination of the individual set-point and reference range. In practice this means that population-based reference ranges are necessary but that it is important to recognize their limitations for use in individuals. Serum TSH responds with amplification to minor alterations in T(4) and T(3). A consistently abnormal TSH probably indicates that T(4) and T(3) are not normal for the individual even when inside the laboratory reference range. This underlines the importance of TSH in diagnosis and monitoring of thyroid dysfunctions. Also, it implies that subclinical thyroid disease may be defined in purely biochemical terms. Under critical circumstances such as pregnancy where normal thyroid function is of importance for fetal brain development, subclinical thyroid disease should be treated. Even TSH within the reference range may be associated with slightly abnormal thyroid function of the individual. The clinical importance of such small abnormalities in thyroid function in small children and pregnant women for brain development remains to be elucidated.
Circadian Rhythm↗
Iodine intake and prevention of thyroid disorders: surveillance is needed.
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Australia↗
Association of tobacco smoking with goiter in a low-iodine-intake area.
BACKGROUND: Goiter development depends on genetic and environmental factors. The major environmental factor is iodine intake, whereas diverging results have been published concerning the association between smoking and goiter. METHODS: A comparable, cross-sectional study was performed of patients from 2 areas in Denmark with mild and moderate iodine deficiency. A random sample of women and men in selected age groups from the general community was investigated; 4649 subjects participated. Smoking habits were investigated with questionnaires and interviews. Ultrasonography and clinical examination of the thyroid were performed, serum thyroglobulin was measured, and iodine concentration in spot urine samples was analyzed. Data were analyzed in linear models and logistic regression analyses. RESULTS: Serum thyroglobulin level and thyroid volume at ultrasonography were positively associated with smoking habits (P<.001); the association was stronger in the area with the lowest iodine intake (interaction: P<.001 for thyroglobulin, P =.04 for thyroid volume). A positive association with smoking was also found for thyroid enlargement (odds ratio, 2.9; 95% confidence interval, 2.2-3.7) and palpable goiter (odds ratio, 3.1; 95% confidence interval, 1.6-5.8). Ex-smokers had a goiter prevalence close to that of never smokers. The fraction of goiter cases attributable to smoking was 49% (95% confidence interval, 29%-65%). CONCLUSIONS: Thyroid volume and goiter prevalence were closely associated with smoking habits, with the strongest association being found in the area with the most pronounced iodine deficiency. This may have implications for future goiter prevalences in Third World countries, with their increasing use of tobacco. Half of goiter cases in this population could be ascribed to smoking.
Adolescent↗
Surveyance of disease frequency in a population by linkage to diagnostic laboratory databases. A system for monitoring the incidences of hyper- and hypothyroidism as part of the Danish iodine supplementation program.
UNLABELLED: In Denmark an increase in iodine intake through salt iodization has been introduced in 1998. In parallel a program for surveyance of thyroid diseases in the population was developed as recommended by UNICEF and WHO. OBJECTIVE: To develop and evaluate a computer based system to identify and register new cases of hyper- and hypothyroidism in a well defined cohort, by linkage to diagnostic laboratory databases. DESIGN AND RESULTS: (1) Two sub cohorts for monitoring were defined (n=535,859), and evaluated to minimize loss of new cases. Collaboration was established with laboratories covering thyroid hormone analyses in the cohort; (2) a diagnostic algorithm was defined and evaluated against clinical practice; (3) evaluation of the laboratory methods employed by the four participating laboratories, to ensure they would reach the same diagnosis in a patient; (4) a register database was developed which used data imported from the laboratory databases to automatically identify previously unknown cases of hyper- and hypothyroidism and record diagnostic activity in the area. All parts of the registration were carefully evaluated. CONCLUSION: We describe for the first time a computer based system for prospective measuring the incidence rate of hyper- and hypothyroidism. The system is particularly useful for monitoring of iodine supplementation programmes.
Databases, Factual↗
Fracture risk is increased in patients with GH deficiency or untreated prolactinomas--a case-control study.
OBJECTIVE: The pituitary secretes many hormones of significance to bone turnover and thus skeletal integrity. The aim of this study was to examine fracture risk in patients with pituitary disorders with special reference to GH deficiency and hyperprolactinaemia. DESIGN: Case-control study. MEASUREMENTS: Fracture occurrence. PATIENTS: A self-administered questionnaire was issued to 537 consecutive patients with pituitary disorders excluding Cushing's disease. A total of 426 (79%) returned the questionnaire and 422 of these could be analysed. Each respondent was compared to three age- and gender-matched control respondents to the same questionnaire drawn randomly from the background population. RESULTS: The patients had a mean age of 51.4 +/- 14.8 years. One hundred and eight patients had acromegaly, 86 had prolactinomas, 136 had non-functioning pituitary adenomas (NFPA), 23 had craniopharyngiomas, and 73 had other types of pituitary disorders. For the total group the fracture risk was not elevated either before or after confirmed diagnosis compared to controls. However, among the patients with prolactinomas, the fracture risk was significantly increased before (relative risk, RR = 1.6, 95% CI: 1.1--2.3) but not after diagnosis. In patients with NFPA, fracture risk was borderline significantly elevated following diagnosis (RR = 1.6, 95% CI: 1.0--2.6). Patients with subnormal stimulated peak GH values suggestive of GH deficiency had a significantly higher risk of fractures after diagnosis than patients who had normal stimulated peak GH values (odds ratio, OR = 4.90, 95% CI: 1.10--21.88). CONCLUSIONS: Untreated prolactinomas were associated with a significant increase in fracture risk. Growth hormone deficiency was also associated with a higher fracture risk.
Adenoma↗
Low goitre prevalence among users of oral contraceptives in a population sample of 3712 women.
OBJECTIVE: Goitre occurs primarily in women. As oestrogens may be an aetiologic factor, the use of oral contraceptives (OC) could be associated with an increased risk of goitre. This is supported by experimental data, but a recent population study suggested decreased thyroid volumes among users of OC. DESIGN: Cross-sectional, observational study. PARTICIPANTS: A random population sample of 3712 women from two Danish cities. MEASUREMENTS: Ultrasound and clinical examination of the thyroid, measurement of serum TSH, T3, T4 and thyroglobulin, and personal interviews with registration of use of OC or post-menopausal oestrogen therapy. Data were analysed in linear models and logistic regression adjusting for age and iodine status. RESULTS: Thyroid volume was lower among users than non-users of OC, 11.1 ml vs. 12.1 ml (P < 0.001). Use of OC was correspondingly associated with a reduced prevalence of thyroid enlargement on ultrasound (odds ratio 0.53, 95% confidence interval 0.37-0.74) and of palpable and visible goitre (OR 0.24, 95% CI 0.07-0.81). Serum TSH was 1.24 mU/l in non-users of OC and 1.35 mU/l in users (P = 0.002). The percentage of goitre cases prevented by OC compared to a hypothetical population without use of OC was 29%. Post-menopausal oestrogen therapy showed similar, but statistically non-significant, associations. CONCLUSION: Use of oral contraceptives was associated with a lower thyroid volume and reduced risk of goitre, and clinically evident goitre was four times more frequent among non-users than among users of oral contraceptives.
Adolescent↗
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.
Adolescent↗
Use of dietary supplements in Denmark is associated with health and former smoking.
OBJECTIVES: To describe the use of dietary supplements in a group of Danish adults and to investigate the differences between users and non-users with respect to age, gender, health and lifestyle factors. DESIGN: Cross-sectional study in two Danish cities. SETTING: The Danish Investigation on Iodine Intake and Thyroid Diseases, 1997-1998. SUBJECTS: Participants were 3707 women (selected age groups between 18 and 65 years) and 942 men (60-65 years). Participation rate was 50%. Supplement data were collected in a personal interview. Data on education, smoking, alcohol intake, physical activity, use of medication and self-perceived health were derived from a self-administered questionnaire. Multiple logistic regression was used for the statistical analysis. RESULTS: Participants were asked about all kinds of supplements, ranging from products containing vitamins and minerals, to fish oils and products of herbal origin. On average 59% reported use of some kind of dietary supplement. Most common were combined multivitamin/mineral products (48%) followed by single vitamin C products (10%). Twelve per cent used three or more different supplements. Supplement use was strongly associated with age and gender, being highest among elderly women (78%). Ex-smokers were more likely to use supplements than subjects who had never smoked (odds ratio (OR) 1.36, 95% confidence interval (CI) 1.09-1.76). Supplement use was more likely among subjects who had many days of illness 95% CI 1.12-1.66) and among users of medication 95% CI 1.04-1.42). Subjects who perceived their health as poor were more likely to use supplements other than just a multivitamin/mineral tablet 95% CI 1.31-3.77). CONCLUSIONS: Use of dietary supplements was related to age, gender and smoking, but also to poor self-perceived health status and absence from work. This indicates that a group of people use supplements as a form of self-medication.
Adolescent↗
Smoking as a risk factor for Graves' disease, toxic nodular goiter, and autoimmune hypothyroidism.
To study the association between smoking and thyroid disease (Graves' disease [E05.0], nodular toxic goiter [E05.2], and autoimmune hypothyroidism [E03.9]) in a low-iodine intake area a case-control study was undertaken. A self-administered questionnaire was issued to 864 consecutive patients with hyperthyroidism and 628 patients with autoimmune hypothyroidism treated at five university or regional endocrinologic clinics in Denmark between January 1, 1990 and December 31, 1998. Each respondent was compared to an age- (+/- 5 years) and gender-matched normal control person randomly drawn from the background population. A total of 621 patients with hyperthyroidism (72%) and 411 patients with autoimmune hypothyroidism (66%) responded. Of these, 617 (542 females) and 408 (364 females) could be analyzed, respectively. There was an increased risk of both Graves' disease (odds ratio [OR] = 2.5, 95% confidence interval [CI]: 1.8-3.5), toxic nodular goiter (OR = 1.7, 95% CI: 1.1-2.5), and autoimmune hypothyroidism (OR = 1.5, 95% CI: 1.1-2.1) with ever smoking compared to never smoking in women, but not in men. With the high proportion of ever-smokers among women (56%), the attributable risk of smoking in women was 45% in Graves' disease, 28% in toxic nodular goiter, and 23% in autoimmune hypothyroidism. Ever use of oral contraceptives was associated with a slightly lower risk of Graves' disease in women, but not of toxic nodular goiter or autoimmune hypothyroidism. In conclusion, smoking is a powerful risk factor for thyroid disease, especially in populations with a high smoking frequency. Oral contraceptive use is associated with a slightly lower frequency of Graves' disease.
Adult↗