Thyroid abnormalities are common in all populations, but it is difficult to compare results of epidemiological studies, because different methods have been used for evaluation. We studied the importance of the population iodine intake level for the prevalence rate of various thyroid abnormalities in elderly subjects. Random samples of elderly subjects (68 yr) were selected from the central person registers in Jutland, Denmark, with low (n = 423) and, in Iceland, with longstanding relatively high (n = 100) iodine intake. Females from Jutland had a high prevalence of goiter or previous goiter surgery (12.2%), compared with males from Jutland (3.2%) and females (1.9%) and males (2.2%) from Iceland. Abnormal thyroid function was very common in both areas, with serum TSH outside the reference range in 13.5% of subjects from Jutland and 19% of those from Iceland. In Jutland, it was mainly thyroid hyperfunction (9.7% had low, 3.8% had high serum TSH), whereas in Iceland, it was impaired thyroid function (1% had low, 18% had high serum TSH). All subjects with serum TSH more than 10 mU/L had autoantibodies in serum, but antibodies were, in general, more common in Jutland than in Iceland. Thus, thyroid abnormalities in populations with low iodine intake and those with high iodine intake develop in opposite directions: goiter and thyroid hyperfunction when iodine intake is relatively low, and impaired thyroid function when iodine intake is relatively high. Probably, mild iodine deficiency partly protects against autoimmune thyroid disease. Thyroid autoantibodies may be markers of an autoimmune process in the thyroid or secondary to the development of goiter.

The biodiversity of culturable acidophilic microbes in three acidic (pH 2.7-3.7), metal-rich waters at an abandoned subarctic copper mine in central Norway was assessed. Acidophilic bacteria were isolated by plating on selective solid media, and dominant isolates were identified from their physiological characteristics and 16S rRNA gene sequences. The dominant iron-oxidizing acidophile in all three waters was an Acidithiobacillus ferrooxidans-like eubacterium, which shared 98% 16S rDNA identity with the type strain. A strain of Leptospirillum ferrooxidans was obtained from one of the waters after enrichment in pyrite medium, but this iron oxidizer was below detectable levels in the acidic waters themselves. In two sites, there were up to six distinct heterotrophic acidophiles, present at 10(3) ml(-1). These included Acidiphilium-like isolates (one closely related to Acidiphilium rubrum, a second to Acidiphilium cryptum and a third apparently novel isolate), an Acidocella-like isolate (96% 16S rDNA identity to Acidocella facilis) and a bacterium that shared 94.5% 16S rDNA identity to Acidisphaera rubrifaciens. The other numerically significant heterotrophic isolate was not apparently related to any known acidophile, with the closest match (96% 16S rDNA sequence identity) to an acetogen, Frateuria aurantia. The results indicated that the biodiversity of acidophilic bacteria, especially heterotrophs, in acidic mine waters may be much greater than previously recognized.

Abstract. One hundred and twenty-four patients with newly diagnosed hyperthyroidism received a combined thionamid-thyroxine medical therapy for approximately 2 years. According to the estimated goitre size before therapy and the type of goitre the patients were divided into 4 groups: Graves' disease no goitre (n = 19). Graves' disease small goitre (n = 57), Graves' disease medium or large goitre (n = 23), multinodular goitre (n = 25). The median follow-up period after cessation of medication was 64 (range 11–141) months. The remission rates in the different groups during follow-up were calculated using life table analysis. Graves' patients with no goitre or a small goitre had a significantly better outcome (remission % after 5 years 82.5 ± 15.4 (se) and 71.5 ± 7.8, respectively) than Graves' patients with a medium size or large goitre (remission % after 5 years 37.0 ± 11.1) (P <0.025). Most patients with multinodular goitre had a relapse within the first year after stop of medication (remission % after 5 years 15.5 ± 10.1). Hence patients with Graves' disease having a small thyroid gland should be treated medically while surgery or radioiodine may be a more reasonable choice in Graves' patients with medium size or large goitres. Medically treated patients with toxic multinodular goitres have a very small chance of prolonged remission if medication is stopped.

Knowledge of the effect of differences in iodine intake levels on public health in areas with no endemic goiter is limited. Groups at risk when iodine intake is relatively low are pregnant and lactating women and their newborns. A prospective randomized study was performed to evaluate the effect of iodine supplementation in an area where the median daily iodine excretion in urine is around 50 micrograms. Fifty-four normal pregnant women were randomized to be controls or to receive 200 micrograms iodine/day from weeks 17-18 of pregnancy until 12 months after delivery. In the control group, serum TSH, serum thyroglobulin (Tg), and thyroid size showed significant increases during pregnancy. These variations were ameliorated by iodine supplementation. Iodine did not induce significant variations in serum T4, T3, or free T4. Cord blood Tg was much lower when the mother had received iodine, whereas TSH, T4, T3, and free T4 levels were unaltered. The results suggest that a relatively low iodine intake during pregnancy leads to thyroidal stress, with increases in Tg release and thyroid size. However, the thyroid gland is able to adapt and keep thyroid hormones in the mother and the child normal, at least under normal circumstances, as evaluated in the present study. It is not known whether this stress is sufficient to be of importance for late development of autonomous thyroid growth and function.

Several studies have demonstrated that the iodine intake is relatively low in Denmark. However, the results are difficult to interpret because no information has been given on the frequency of individual iodine supplementation. We performed a cross-sectional study of elderly subjects living in the commune of Randers, Denmark. Urinary iodine excretion was measured in the 423 participants (185 males, 238 females) and a careful history was taken on any possible intake of supplementary iodine. The median urinary iodine excretion was 48.3 micrograms/g creatinine for the whole population (40.8 micrograms/g creatinine in males, 53.2 micrograms/g creatinine in females). In the part of the population that did not take iodine supplementation (46.7%) the median value was 36.1 micrograms/g creatinine (males 33.8; females 38.8). Regular iodine supplementation taken as an iodine-containing vitamin/mineral tablet was found in 30.8% of the population. This increased the urinary iodine excretion to a median level of 80.5 micrograms/g creatinine (males 62.0; females 88.0). The study shows that the basic iodine intake level is overestimated if individual iodine supplementation is not taken into account. Such supplementation may lead to median iodine excretion values that seem reasonable, even if the iodine intake of the part of the population not taking iodine (in this study, nearly half of the population) is low.