Single and multiple selenium-zinc-iodine deficiencies affect rat thyroid metabolism and ultrastructure.

This study was conducted to evaluate the effects of single and combined deficiencies of Se, Zn and I on thyroid function in rats. Rats were fed amino acid-based diets for 6 wk starting from weaning. The diets contained either low or adequate amounts of these minerals. In addition to the control and control pair-fed groups, seven experimental groups were formed: Se deficient (Se-); I deficient (I-); Zn deficient (Zn-); Se and I deficient (Se-I-); Zn and I deficient (Zn-I-); Se and Zn deficient (Se-Zn); and Se, I and Zn deficient (Se-I-Zn-). Serum triiodothyronine (T3) was significantly lower than in controls in Zn-, Se-Zn- and Se-I- groups. Serum total thyroxine (T4) and free T4 were significantly lower and thyroid-stimulating hormone (TSH) greater in all iodine-deficient groups, regardless of Se or Zn status. Thyroid glutathione peroxidase activity was significantly reduced in Se- and Se-Zn- groups. Nevertheless, in the groups with a concurrent I deficiency, the activity of this enzyme was significantly greater than in controls. Severe alterations of the follicle cellular architecture, including signs compatible with apoptosis, were observed in the Zn- and Se-Zn- groups. These alterations appeared to be less severe when iodine deficiency was simultaneously present. Single and multiple deficiencies of Se, Zn and I have distinct effects on thyroid metabolism and structure.

[Iodine nutrition in school children of four census areas of Chile]. / Nutrición de yodo en escolares de cuatro zonas censorias de Chile.

BACKGROUND: Although endemic goiter is an easily controlled chronic disease, it continues to be a serious global public health problem. AIM: To study iodine nutrition in school age children from different areas of Chile. SUBJECTS AND METHODS: Thyroid gland was palpated in 4181 school age children from Calama, Santiago, Temuco and Punta Arenas. Urinary iodine excretion was measured to 9% of these children and iodine concentration in salt for human consumption obtained in each of these areas was determined. RESULTS: A 9% goiter prevalence in boys and 11% prevalence in girls was detected. The prevalence of goiter Ia was 6.5% and the figure in different geographic areas was similar. Iodine concentration in salt for human consumption was adequate according to Chilean legislation (82.6, 95.7, 96.8 and 93.2 micrograms ugI/g salt in Calama, Santiago, Temuco and Punta Arenas respectively). Urinary iodine excretion in boys and girls was 1695 and 1802 micrograms l/g creatinine in Calama, 680 and 732 in Santiago, 574 and 690 in Temuco, 570 and 528 in Punta Arenas. These values are well above recommendations. CONCLUSIONS: Endemic goiter is no longer a problem in Chile. The importance of a continuous surveillance of iodine nutrition in Chile and the reduction of salt iodine concentration required by Chilean legislation is underscored.

[Bone mineralization in adolescents suffering from postnatal malnutrition]. / Mineralización ósea en adolescentes que padecieron desnutrición postnatal temprana.

The bone mineralization of 6 male and 18 female adolescents with a mean age of 12 years and 11 months, who had suffered severe, early, postnatal protein-energy undernutrition, was analyzed. These patients have been followed up at our Institute since their nutritional rehabilitation. Bone mineralization was measured by bone dual isotopic densitometry (Gd 153). These results were compared with those of normal school-age Chilean children of the same age and sex. Weight for height of adolescent who had suffered from undernutrition was similar to the controls, and both were over 100% of the standard. Adequation of height for age was significantly less in those with previous history of undernutrition. Densitometries showed that adolescents with a past history of undernutrition had lower total bone mass in whole body, spine and femoral neck; differences disappeared when expressed per 100 cm of body height. There were no differences in bone mineral density in the different area measurements. It is concluded that the possible alterations that undernutrition produces in bone mineralization probably recover after nutritional rehabilitation, adequate nutritional follow up and health support.

LH-releasing activity of hypothalamic extracts not attributable to GnRH.

LH secretion is under hypothalamic control, mostly through GnRH. Hypothalamic extracts stimulate LH release in vitro, an action usually attributed to the presence of GnRH. However, the presence of other LH-releasing factors cannot be ruled out since there are other neuromediators endowed with the capacity to influence LH release. We analyzed the presence of an LH-releasing activity in bovine median eminence extracts (ME extracts) different from GnRH using cultured rat pituitary cells. Both, GnRH and ME extracts caused a dose-dependent stimulation of LH release. The maximum response obtained with ME extracts (up to 10-fold the respective baseline) was significantly greater than the maximum response obtained with GnRH (up to 5-fold the respective baseline). Monoclonal or polyclonal GnRH antibodies in the solid phase completely eliminated the LH-releasing activity of 10(-7) M GnRH; in contrast, they only partially removed the activity present in ME extracts. The GnRH receptor blocker, Nal-Glu, 10(-7) M, which completely blocked the effect of GnRH could not totally suppress the LH-releasing activity of ME extracts. These findings indicate that ME extracts contain, in addition to GnRH, an LH-releasing activity not attributable to GnRH because it differs in its immunoreactivity and in its ability to stimulate LH release when GnRH receptors are blocked.