Iodine status in Danish pregnant and breastfeeding women including studies of some challenges in urinary iodine status evaluation.

Denmark was previously iodine deficient with regional differences. Moderate iodine deficiency appeared in West Denmark and mild iodine deficiency in East Denmark and also Danish pregnant and breastfeeding women suffered from iodine deficiency. The Danish mandatory iodine fortification of salt was introduced in the year 2000 and has increased iodine intake in the Danish population. However, median urinary iodine concentration in the general population and in pregnant and breastfeeding women is still below the level recommended, corresponding to mild iodine deficiency. Certain characteristics may challenge the evaluation of urinary iodine status in pregnancy and during breastfeeding. This review also addresses methodological challenges related to spot urine sampling conditions and the use of iodine supplement and discusses the use of non-pregnant population groups as a proxy for iodine intake in pregnant women.

Narrow individual variations in serum T(4) and T(3) in normal subjects: a clue to the understanding of subclinical thyroid disease.

High individuality causes laboratory reference ranges to be insensitive to changes in test results that are significant for the individual. We undertook a longitudinal study of variation in thyroid function tests in 16 healthy men with monthly sampling for 12 months using standard procedures. We measured serum T(4), T(3), free T(4) index, and TSH. All individuals had different variations of thyroid function tests (P < 0.001 for all variables) around individual mean values (set points) (P < 0.001 for all variables). The width of the individual 95% confidence intervals were approximately half that of the group for all variables. Accordingly, the index of individuality was low: T(4) = 0.58; T(3) = 0.54; free T(4) index = 0.59; TSH = 0.49. One test result described the individual set point with a precision of +/- 25% for T(4), T(3), free T(4) index, and +/- 50% for TSH. The differences required to be 95% confident of significant changes in repeated testing were (average, range): T(4) = 28, 11-62 nmol/liter; T(3) = 0.55, 0.3--0.9 nmol/liter; free T4 index = 33, 15-61 nmol/liter; TSH = 0.75, 0.2-1.6 mU/liter. Our data indicate that each individual had a unique thyroid function. The individual reference ranges for test results were narrow, compared with group reference ranges used to develop laboratory reference ranges. Accordingly, a test result within laboratory reference limits is not necessarily normal for an individual. Because serum TSH responds with logarithmically amplified variation to minor changes in serum T(4) and T(3), abnormal serum TSH may indicate that serum T(4) and T(3) are not normal for an individual. A condition with abnormal serum TSH but with serum T(4) and T(3) within laboratory reference ranges is labeled subclinical thyroid disease. Our data indicate that the distinction between subclinical and overt thyroid disease (abnormal serum TSH and abnormal T(4) and/or T(3)) is somewhat arbitrary. For the same degree of thyroid function abnormality, the diagnosis depends to a considerable extent on the position of the patient's normal set point for T(4) and T(3) within the laboratory reference range.

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.

More hypothyroidism and less hyperthyroidism with sufficient iodine nutrition compared to mild iodine deficiency--a comparative population-based study of older people.

OBJECTIVE: To assess the occurrence of thyroid disorders and autoimmunity in a geriatric population with long-standing recommended iodine intake of natural origin compared to mild iodine deficiency. DESIGN AND SETTING: Cross-sectional, comparative, population-based study in two areas with different iodine intakes due to different tap water iodine contents. PARTICIPANTS: Residents of Randers (n=212) or Skagen (n=218), Denmark, aged 75-80 years. MEASURES: Blood samples were collected for measuring thyrotropin (TSH), triiodothyronine, thyroxine, thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TGAb), thyroglobulin (TG); iodine excretion estimated from iodine and creatinine measured in spot urine samples; questionnaire on history of thyroid disease, medication and vitamin use; clinical examination of the neck. RESULTS: Median urinary iodine excretion was 50 microg/24h in Randers and 177 microg/24h in Skagen (p<0.001). A history of thyroid disease was reported by 40 (9.3%) dominated by goitre (n=22) in Randers and hypothyroidism and Graves Disease (n=15) in Skagen (p<0.001). We found visible goitre in 26% of Randers dwellers and none in Skagen (p<0.001). Hyperthyroidism with TSH below the reference range was present in 26% of Randers and 6% of Skagen dwellers while 6% and 13%, respectively, were hypothyroid with TSH above the reference range (p<0.001). More Randers than Skagen participants harboured a thyroid antibody (42% vs. 32%, p=0.006). CONCLUSIONS: Recommended iodine intake associated with more hypothyroidism, less hyperthyroidism and goiters, low TGAb prevalence and lower TG level in serum than did iodine deficiency. TPOAb was similar in the iodine replete and deficient geriatric populations.

[Basic registration of risk factors in medical records. Malnutrition, overweight, physical inactivity, smoking and alcohol]. / Basale journaloplysninger om risikofaktorer. Underernaering, overvaegt, fysisk inaktivitet, rygning og alkohol.

INTRODUCTION: Lifestyle factors are important for clinical outcome. Systematic and early identification of these factors is important in order to offer relevant lifestyle intervention programmes. The objective was to evaluate whether basic registration of risk factors was understandable, applicable and sufficient in the clinical workday. MATERIALS AND METHODS: Eleven clinical specialists participated from a broad range of departments. They performed identification and registration of malnutrition, overweight, physical inactivity, smoking and harmful alcohol consumption based on medical records from own departments (in total 2420 times). The specialists then evaluated the understanding, applicability and sufficiency (363 times). Their comments were noted. RESULTS: Identification and registration was accomplished for 85% (0-100%) of the records. Except for two fields--"measurements of waist" and "other training programs"--the specialists found the basic registration understandable, applicable and sufficient. They lacked more details regarding stress-response in the information material and pointed out inconsistencies in the wording. Ten specialists found that the recommended clinical approach was possible to implement in the present routines. CONCLUSION: Basic registration of lifestyle factors for adult patients is possible and clinical relevant. It is recommended that the Danish National Board of Health uses the results in future.