Abstract

DE ROSSO, Villagrán et al. Phothoperiod and Environmental Temperature Effects on Plasmatic Levels of Thyroid Stimulating Hormone (TSH). Rev. argent. endocrinol. metab. [online]. 2013, vol.50, n.3. ISSN 1851-3034.

Studies carried out in Alto Valle del Rio Negro, Patagonia Argentina, show a prevalence of goiter slightly above the cut-off line established by the International Council for the Control of Iodine Deficiency Disorders (IC-CIDD), with an appropriate iodine nutrition grade; such prevalence could be attributed to environmental and/ or nutritional factors that interfere with thyroid metabolism. Blood TSH concentration responds to circadian variations and is influenced by seasonality and environmental temperature. The geographic characteristics, semi-desert climate or the presence of endocrine disruptors are factors that could be related to hormonal production modifications in urban or rural areas. Objectives: a) To evaluate the potential association between annual variation in TSH levels, photoperiod and environmental temperature. b) To estimate if plasma TSH values are significantly different in populations from rural and urban areas in Alto Valle del Rio Negro. We retrospectively evaluated 1393 healthy patients living in Alto Valle del Río Negro: 226 males and 1167 females, who presented for routine clinical check-up during 2010. SPSS 17.0 software was used for the analysis. Significant variations were found in Log-TSH, with a maximal peak at the beginning of the fall-winter and a minimal peak in spring-summer. There is a significant difference in the values of TSH between rural and urban areas, (values of Log-TSH in rural area: 0.46 uUI/ml (0.30-0.61) vs. urban area: 0.28 uUI/ml (0.26-0.30) with p<0.001). Seasonal variation results are indicative of the body adaptation to changes in environmental conditions. The significant difference in TSH values in rural areas vs. urban areas would indicate that rural residents are exposed to environmental factors including those derived from fruits and vegetables production. We suggest taking into account these findings for both populations studied in the region Alto Valle del Río Negro at the time of diagnostic evaluation and subsequent treatment of thyroid dysfunction.

Keywords : Thyroid; Seasonal variations; Oxidative stress.

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