Relationship between meteorological factors and the pituitary-thyroid axis in healthy men living in the Subarctic

BACKGROUND: The changing seasons in the subarctic region causes an adaptive restructuring of the inhabitants’ organisms. The most healthy individuals can adjust to the Northern climate without developing health disorders. However, a decrease in adaptive reserves may result in various pathological conditions. Extensive studies across different populations in various climatic zones have reported significant associations between meteorological factors and the fluctuations in thyroid hormones. AIM: To assess the influence of circannual dynamics of meteorological factors on the serum levels of thyroid hormones and thyroxin-binding globulin (TBG) in men living in subarctic environmental conditions. MATERIAL AND METHODS: An prospective analytical study was conducted in the city of Arkhangelsk (64°32´24.4˝ N). Twenty clinically healthy men comprised the sample. Blood samples were collected every 3 months over a 12-months period. Subjects with any factors affecting the hypothalamic-pituitary-thyroid axis were excluded. Circannual variation in the studied characteristics were analyzed using Wilcoxon signed-rank tests with Bonferroni correction. Associations between hormonal data and climatic data were assessed using Spearman’s correlation coefficients. RESULTS: The thyroid-stimulating hormone reached its peak, while T4 and TBG were at their lowest during the period of minimal daylight hours in December. This coincided with the highest values of relative humidity and atmospheric pressure. Furthermore, T4 and TBG positively correlated with the duration of daylight and outdoor temperature at the day of samples collection, while showing an inverse correlation with atmospheric pressure and average monthly relative humidity. Т3 and T4 inversely correlated with average monthly atmospheric pressure. T3 was positively associated with the duration of daylight. CONCLUSION: The key environmental factors affecting the health people living in Northern regions include are the duration of daylight, outdoor temperature, monthly atmospheric pressure, and relative humidity. It is important to note that the impact of these climatic conditions on human health varies across the regions. Thus, our findings cannot be generalized to other areas..