Triiodothyronine, DHEAS/cortisol index and daily oscillations of hormones as markers of adaptation to occupational loads in the Arctic: results of hormonal status study in firefighters-rescuers of EMERCOM of Russia

Relevance. Considering that prolonged stress of adaptive mechanisms is associated with an increase in the risk of developing somatic pathology, it is relevant to search for laboratory markers that allow assessing the adaptive status of men working in the Arctic and exposed to the combined effects of occupational stress factors and “polar stress”.Intention. To substantiate directions of scientific search for laboratory markers of adaptation to occupational loads in the Arctic.Methodology. A laboratory examination was performed on 74 practically healthy firefighters-rescuers from 22 to 49 years old, working in the Arctic zone of the Russian Federation. Those examined were divided into groups depending on the conditions of occupational activity, as well as triiodothyronine levels, the adaptive androgen dehydroepiandrosterone sulfate (DHEAS) / cortisol index and the cortisol morning/cortisol evening ratio. The results of the hormonal status study were evaluated.Results and Discussion. Significant differences in triiodothyronine levels were revealed between the groups of local and visiting firefighters-rescuers, with no difference in age and concentrations of thyroid-stimulating hormone and free thyroxine.Firefighters-rescuers who were local residents of the Arctic and had low levels of triiodothyronine tended to a relative androgen deficiency. In firefighters-rescuers with preserved adaptive reserves, DHEAS / cortisol index increased with increasing workload in terms of the number of emergency response trips. In rescuers with HEAS / cortisol index < 2.1, there was no such correlation, and higher index values correlated with a more pronounced rhythm of the daily secretion of triiodothyronine and free thyroxine. In the group with the most pronounced daily rhythm of cortisol secretion, a physiological increase in thyroidstimulating hormone concentration was determined in the evening hours along with uniform prolactin secretion throughout the day. A group with a smoother rhythm of cortisol secretion tended to increased evening secretion of prolactin and smoothened rhythm of thyroid-stimulating hormone production.Conclusion. The data obtained are consistent with current ideas about the polysystemic adaptive response, suggest joint activation of the adrenal and pituitary-thyroid mechanisms of adaptation to occupational loads in the Arctic and indicate the necessity of further study and application of the DHEAS / cortisol index and triiodothyronine, as well as daily oscillations of thyroid hormones, thyroid-stimulating hormone and prolactin as markers of adaptation.