Biomedical subjects

Nils Knudsen

Publications and source records attributed to Nils Knudsen.

22 records · Page 2Linked to original sources

PubMed2002

Thiocyanate in food and iodine in milk: from domestic animal feeding to improved understanding of cretinism.

Transport of iodine in the mammary gland into breast milk plays a central role in various fields of prevention of thyroid diseases. First, a sufficient content of iodine in the mother's milk is necessary for normal brain development in the breastfed child. This is attained by expression during lactation in the mammary gland of the sodium iodide symporter (NIS), also responsible for iodine transport in the thyroid. Milk iodine content varies with the iodine intake of the mother, and urinary iodine excretion in groups of mothers seems to be a valuable indicator of the iodine status of their breastfed children. Second, iodine in dairy products provides a considerable part of iodine intake in many populations. Thiocyanate from rapeseed feeding of cows decreases milk iodine content, probably by competitive inhibition of NIS in the mammary gland. Alterations in feeding of dairy cows may alter the iodine content of consumer milk, and this may influence the risk of thyroid diseases in the population. Thiocyanate inhibition of iodine transport into milk may also be operative in humans with a high thiocyanate intake. This could further impair iodine status in breastfed children in low-iodine intake areas of the world. It can be speculated that a low-iodine content of mother's milk because of inhibition of NIS in the mammary gland may be one factor of importance for development of myxedematous cretinism.

Animal Feed↗

PubMed2002

Relations between various measures of iodine intake and thyroid volume, thyroid nodularity, and serum thyroglobulin.

BACKGROUND: Iodine intake can be measured in various ways, and each method may have advantages and disadvantages. OBJECTIVE: We sought to investigate the potential associations of various measures of iodine intake with thyroid volume, prevalence of thyroid nodules, and serum thyroglobulin. We also sought to identify, if possible, groups at risk of thyroid disease because of their food choices. DESIGN: This cohort study included 4649 randomly selected subjects with mild-to-moderate iodine deficiency; the subjects lived in 2 cities in Denmark. Iodine intake was estimated by using a food-frequency questionnaire and by measuring iodine excretion in spot urine samples. Thyroid volume and nodularity were measured with ultrasonography. RESULTS: In multiple linear regression models, significant inverse relations were found between thyroid volume and estimated 24-h iodine excretion, iodine intake from diet plus supplements, iodine intake from diet/kg body wt, and milk intake (P = 0.001 for all), but not urinary iodine excretion measured as a concentration (P = 0.40). All measures of iodine intake were significantly related to serum thyroglobulin concentration (P <or= 0.002), but only some measures of iodine intake were significantly related to the prevalence of thyroid nodules. CONCLUSIONS: Even in a geographic area where mild iodine deficiency is common, a significant relation between iodine intake and thyroid volume was found. All measures of iodine intake, except iodine excretion measured as a urinary concentration, predicted thyroid volume. Serum thyroglobulin concentration appears to be a good marker of iodine status. Subgroups with low intakes of milk and milk products had an increased risk of thyroid disease.

Adult↗

PubMed2002

Large differences in incidences of overt hyper- and hypothyroidism associated with a small difference in iodine intake: a prospective comparative register-based population survey.

Around 3-4 billion people in the world are covered by iodine supplementation programs to prevent developmental brain damage and other iodine deficiency (ID) disorders. Mild ID is associated with more hyperthyroidism and less hypothyroidism in the population than a high iodine intake. Knowledge of the iodine intake levels where the shifts in incidences occur is important for planning of iodine supplementation programs. A computer-based register linked to thyroid diagnostic laboratories was used to continuously identify all new cases of overt hyper- and hypothyroidism in two population cohorts with moderate and mild ID, respectively (Aalborg, n = 310,124; urinary iodine, 45 micro g/liter; and Copenhagen, n = 225,707; urinary iodine, 61 micro g/liter). The investigation was initiated before iodization of salt in Denmark and was part of the monitoring program. In 1997-1998, the incidence rate of overt hyperthyroidism was high in the area with the lowest iodine intake (92.9/100,000 per year) compared with the area with only mild ID (65.4/100,000 per year). Standardized rate ratio was 1.49, and 95% confidence interval was 1.22-1.81. The opposite relationship was present for overt hypothyroidism (moderate ID, 26.5/100,000 per year; mild ID, 40.1/100,000 per year; standardized rate ratio, 0.73; 95% confidence interval, 0.55-0.97). The different incidence rates were confirmed during each of the two following years. The results of this prospective investigation of the incidence of overt hyper- and hypothyroidism suggest that iodine supplementation of a population may increase the incidence of overt hypothyroidism, even if the population is moderately iodine-deficient. In such a population, the increase in risk of hypothyroidism should be weighed against the risk of ID disorders such as hyperthyroidism due to multinodular toxic goiter. The optimal level of iodine intake to prevent thyroid disease may be a relatively narrow range around the recommended daily iodine intake of 150 micro g.

Adolescent↗

PubMed2002

Parity is associated with increased thyroid volume solely among smokers in an area with moderate to mild iodine deficiency.

OBJECTIVE: Pregnancy has been suggested as part of the explanation of the gender difference in the prevalence of goitre, but opposing results have been reported on the association between pregnancy and goitre. We investigated the association between parity and thyroid volume and a possible impact of iodine deficiency and tobacco smoking on this association. DESIGN: A comparative, cross-sectional study of 3712 women randomly sampled from the general population in two geographical areas with moderate and mild iodine deficiency. METHODS: The participants answered questionnaires with an obstetric anamnesis, and ultrasonography of the thyroid was performed. Data were analysed in linear models and logistic regression analysis to adjust for age, iodine status, use of oral contraceptives and smoking habits. Women with present or recent pregnancies were excluded from the analyses. RESULTS: A higher thyroid volume was found among parous than among nulliparous women (P=0.007). The association between parity and thyroid volume was strongest in the youngest age groups, in the region with the most severe iodine deficiency, and among smokers. No association was found between parity and the prevalence of solitary or multiple thyroid nodules. Number of births, age at menarche or menopause, the number of fertile years, and age at first childbirth were not associated with thyroid volume. CONCLUSION: Pregnancy increases thyroid volume, particularly when combined with tobacco smoking and iodine deficiency. The effect is probably reversible seen over a spectrum of several years.

Adolescent↗