[Status of alimentary iodine supply in the Potsdam area]. / Stand der alimentären Jodversorgung im Raum Potsdam.

In the period from November 1995 to April 1996 we have collected 120 samples of 24-h-urine from volunteers of the "Brandenburger Ernährungs- und Krebsstudie". 108 persons--without iodine supplementation--showed an average iodine excretion about 99 micrograms I/g creatinine, and the median value showed 94.2. Only 45.4% of the samples indicated a sufficient iodine supply. In 43.5% an iodine deficiency grade I was registered, and in 11.1% grade II. An iodine deficiency grade III did not occur. Due to the increased use of iodized salt in meat- and cereal products, to intensive public education etc. it seems, that the individual iodine intake is better than some years ago. But the iodine deficiency prophylaxis should be further more continued.

Nitrate-induced hypothyroidism is associated with a reduced concentration of growth hormone-releasing factor in hypothalamic tissue of rats.

Dietary nitrate significantly inhibits the growth of male and female rats. To test the possibility that the growth hormone-releasing factor (GRF) content in hypothalamic tissue is deranged under these conditions, male and female rats were fed a diet containing 3% KNO3 for 6 weeks, compared to a normal diet (4 X 5 animals). The food intake of rats fed nitrate was reduced significantly (23 and 28% resp.). Weight gain was also decreased by 35 and 41% in male and female rats. The mean Sm-C/IGF-I concentration was 1.61 and 1.03 rU/ml in male and female control rats, whereas the concentrations in nitrate-exposed rats were 0.92 and 0.64, respectively (P less than 0.01). The GRF content of hypothalamic tissue also decreased significantly from 407 and 533 ng/g protein in controls to 174 and 229 in treated male and female rats. Nitrate exposure is characterized by hypothyroidism, food intake depression, low Sm-C/IGF-I concentrations in plasma and a decreased hypothalamic GRF content. Independent of the peripheral changes, the content of Sm-C/IGF-I in the brain remains constant. The results of the study demonstrate that thyroid hormone deficiency leads to an inhibition of GH axis already at the hypothalamic level.

Nephrocalcinosis, hypercalciuria and elevated serum levels of 1,25-dihydroxyvitamin D in children. Possible link to vitamin D toxicity.

Ten children age 1 1/2 to 14 years, had bilateral nephrocalcinosis and hypercalciuria, but normal serum calcium (Ca) and phosphate (P) concentrations. Patients with hypercalciuria were divided into absorptive (n = 4) and renal (n = 6) subgroups, and in the latter four patients had a primary Ca-leak and two had a P-leak. All the children had received intermittent high dose vitamin D prophylaxis during infancy. At the time of investigation all had normal serum levels of 25-hydroxyvitamin D, yet all but one had elevated values of 1,25-(OH)2D. Although the hypercalciuria was indistinguishable from the various known forms of idiopathic hypercalciuria, the previous clinical course and the pattern of bone mineral homeostasis suggest that both clinical features, namely nephrocalcinosis and hypercalciuria were related to vitamin D toxicity through various pathogenetic pathways.

[Vitamin D-induced tissue calcinosis and arteriosclerosis changes. I: A contribution to the 60 year history of vitamin D research with special reference to childhood]. / Vitamin-D-bedingte Gewebscalcinosen und arteriosklerotische Veränderungen. Teil I: Ein Beitrag zur 60jährigen Geschichte der Vitamin-D-Forschung unter besonderer Berücksichtigung des Kindesalters.

Already in 1927, a short time after the detection of the vitamin D, the danger of a hypervitaminosis was put into the field of view. Overdoses of vitamin D may effect calciferous infiltrations in the soft tissue and arteriosclerotic changes. These findings are important especially under consideration of the up-to-now large-dosed vitamin-D-application in the field of the rachitis-prophylaxis. The appearance of nephrocalcinoses could have been demonstrated in predisposed infants and children suffering from disorders in calcium metabolism. In order to optimize the rachitis-prophylaxis in the GDR we comment on the problems and dangers by vitamin-D-overdosages on the basis of animal-experimental and clinical examinations.

Intermittent high-dose vitamin D prophylaxis during infancy: effect on vitamin D metabolites, calcium, and phosphorus.

In infants receiving intermittent high dose vitamin D prophylaxis (600,000 IU ergocalciferol per dose orally) every 3-5 mo, the serum concentrations of vitamin D metabolites, calcium (Ca), and phosphorus (P) were determined before and 2 wk after each dose. The 25-hydroxyvitamin D (OHD) concentrations increased to well above normal but the values returned to the normal range before each subsequent dose. The 24,25- and 25,26-dihydroxyvitamin D ([OH]2D) levels followed a pattern similar to that of 25-OHD, and both were closely related to the latter (r = 0.85, p less than 0.005, and r = 0.84, p less than 0.005, respectively). The 1,25-(OH)2D concentrations did not vary in a consistent pattern and remained largely within the normal range. All infants had normal Ca levels before the first dose but 14 infants (34%) later had one or both Ca values above the upper normal limit of 2.80 mmol/L (2.81-3.32 mmol/L), indicating that the vitamin D doses were excessive despite the lack of accumulative increases in serum vitamin D concentrations.

Effect of chronic dietary nitrate and different iodine supply on porcine thyroid function, somatomedin-C-level and growth.

Due to the lately increased oral nitrate intake of humans and animals the influence of 3% KNO3 in the diet on growth and the thyroid hormone and somatomedin-C-concentration in the serum was to be tested in an experiment with growing pigs in case of different iodine supply. The investigations were undertaken in 3 groups with 9 piglets each. The animals were 6 weeks old: 1. nitrate-exposed, 2. pair-fed to group 1 (without nitrate), 3. ad libitum without nitrate. The mean daily weight gains amounted to 242, 274 and 393 g respectively, after a five-week test period. Compared to the ad libitum control group, the T4-, T3-, rT3- and Sm-C-level of nitrate-exposed animals was significantly lower after 5 weeks. There were no statistically relevant differences between nitrate-exposed and pair-fed animals with regard to the T3- and Sm-C-level. After the 5-week test period with an iodine supply covering the requirement the rations of all 3 groups were supplemented with further 0.8 mg iodine/kg. The T4-, T3- and rT3-levels of the animals of group 1 normalized within one week. The Sm-C-levels of the nitrate-exposed and pair-fed group were still decreased. The investigations show that an increased nitrate intake via food and drinking water influences the thyroid hormone metabolism. It should be taken into consideration in the etiology of endemic struma. Furthermore, excessive nitrate intakes influence the Sm-C-concentration and thus growth due to food intake depression.

Influence of phytogenic substances with thyreostatic effects in combination with iodine on the thyroid hormones and somatomedin level in pigs.

Growing pigs were given 8% rape seed meal (RSM), which was offered without or with different iodine-supplements and further trace elements. RSM without I-supplementation reduced food intake and weight gains by more than 50%, thyroid weight increased by the factor 6, T4 declined below the detectable limit, T3 by two thirds and somatomedin activity by 50% compared to the control group (soy bean meal). In spite of supplementation with iodine and further trace elements the T3-level reached the level of the control group in no variant due to nutrient deficiency (reduced food intake) and the conversion-impeding effect of goitrogenic substances. The same is true for Sm-activity and weight gains, whereas the T4-level increased even above the level of control animals due to I-supplementation. There are significant correlations (correlation coefficients 0.77 and 0.64 resp.; p less than 0.001) between food intake and T3-concentration resp. and Sm-activity. This study demonstrate that the reduced growth in case of the intake of phytogenic substances with thyreostatic effects is directed by the diminished food consumption and the peripheral hypothyroid situation via decreased Sm-synthesis. The high content of thyreostatic substances in tissues of rape seed fed animals is a potential danger for the human consumer.