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Previously, differences in the thyroid profile of Arctic residents were shown depending on the vitamin A blood level. However, dietary habits and metabolism peculiarities in the aboriginal and Caucasian representatives of the North population may be the cause of different retinol supply and therefore be one of the reasons for changes in their thyroid activity. The purpose of the research was to assess vitamin A and thyroid blood levels in the aboriginal and local Caucasian population representatives of the Russian Arctic territories. Material and methods . In the single-center observational cross-sectional study, apparently healthy residents of villages in the Arkhangelsk region were examined (n=281): 145 representatives of the local Caucasian population and 136 representatives of the aboriginal population, with the proportion of tundra nomadic aborigines at 34%, village aborigines at 66%. Vitamin A blood serum level was determined by the fluorometric method, and the thyroid content [thyroid stimulating hormone (TSH), thyroxine (T4), triiodothyronine (T3), free T4, free T3] was determined by enzyme immunoassay. The integral thyroid index (ITI) as well as the index of peripheral conversion of iodothyronine (IPC) total and free fractions were calculated. Results . The level of retinol in the indigenous population of the Arctic was lower than that in the local Caucasian population (1.84 [1.26; 2.56] versus 2.10 [1.70; 2.42] μmol/L, p=0.014). However, its deficiency was found only in village aborigines (20.5% of women and 11.8% of men). At the same time, they have the maximum tension of the pituitarythyroid system: lower level of free T3 and free fractions' IPC than in the nomadic and Caucasian population, and TSH levels were higher than in the Caucasian population. Increased vitamin A levels prevailed among the nomadic population: in 60.7% of men and 11% of women retinol level exceeded the norm. At the same time, they have increased metabolic activity of thyroid hormones: higher levels of free T3 and free fractions' IPC compared with sedentary aboriginal population. No pronounced features of the thyroid profile were found in local Caucasians at normal blood concentrations of vitamin A. Conclusion . The lowest retinol levels are observed in settled aborigines (especially young women) living in villages and experiencing the greatest transformation of traditional lifestyle and nutrition, which is combined with higher TSH blood levels and decreased thyroid hormone metabolism. The highest retinol levels were found in nomadic aborigines (especially young men), which increase the reserves of antioxidant defense and support high metabolism of thyroid hormones. However, the high percentage of people with excessive vitamin A blood level in this group raises concerns due to the possible negative consequences. Therefore, it is necessary to monitor fat soluble vitamin levels among Arctic aboriginal populations. Social support measures should be taken for settled residents of villages, enabling them to consume more traditional foods rich in vitamin A. The causes of excessive blood retinol in nomadic aborigines require further study and control., Competing Interests: The authors declare no conflicts of interest., (Copyright© GEOTAR-Media Publishing Group.)

At the present time the prevalence of thyroid diseases keeps growing, so knowledge of the factors affecting thyroid activity is very important. Vitamin A (retinol) is a fat-soluble vitamin with a hormone-like effect that can influence both the expression of thyroidstimulating hormone in the pituitary gland and the synthesis of thyroid hormones. The aim of the research was to study vitamin A serum level and its relationship with the thyroid profile in residents of the Arctic zone of the Russian Federation, depending on gender. Material and methods . In the course of a single-center observational cross-sectional study, 304 apparently healthy residents of villages in the Arkhangelsk region (103 men and 201 women) were examined. The serum concentration of vitamin A was determined by the fluorometric method, and the content of thyroid parameters was determined by the enzyme immunoassay. The integral thyroid index (ITI) and the index of peripheral conversion of iodothyronines (IPC) were calculated. The subjects were divided into 4 groups depending on the quartile of vitamin A. The relative risk of developing subclinical hypothyroidism was calculated with a reduced concentration of vitamin A. Results . The content of vitamin A was 1.97 (1.18; 2.97) μmol/l. Retinol levels in the female population were significantly lower than in the male population (1.85 vs 2.27 μmol/l, p<0.0001). Women in group 1 compared with group 4 showed significantly higher levels of thyrotropin (2.33 vs 1.40 μIU/ml, p=0.0002) and thyroxin (109.8 vs 99.4 nmol/l, p=0.010), while the ITI values, on the contrary, were the lowest (8.12 and 13.85 c.u., p=0.0002). The relative risk calculation showed that vitamin A levels below 1.39 μmol/L increase the risk of subclinical hypothyroidism in women by 2.01 times [95% confidence interval 1.07-3.78]. Men in group 4 compared with group 1 showed a lower content of thyroxin (83.0 vs 109.2 nmol/l, p=0.009) against the background of higher IPC values (0.019 vs 0.016 c.u., p=0.046). Conclusion . In the inhabitants of the Arctic, the content of vitamin A is within the reference values, however, in 24.3% of men, its level is above the norm. In women, the concentration of retinol is significantly lower, and its level of less than 1.39 μmol/l increases the risk of developing subclinical hypothyroidism by 2.0 times. Increased values of vitamin A in the inhabitants of the North cause lower levels of thyroxine and an increase in the peripheral conversion of iodothyronines, which is more pronounced in men., Competing Interests: The authors declare no conflicts of interest., (Copyright© GEOTAR-Media Publishing Group.)

In recent years, there has been a decrease in reproductive potential, especially among residents of the Arctic territories, having the greatest stress from various body systems, including the state of the hormonal regulation of the male reproductive system. The study of the dopamine levels and the content of sex hormones in the male population of various Arctic regions is relevant due to the increased stress on the part of the dopaminergic system and the hypothalamic-pituitary-gonadal axis in residents of the Northern regions, as well as the lack of information about their interaction among the apparently healthy population. The aim of the investigation is to study the possible effect of various plasma concentrations of the dopamine on the content of sex hormones and sex-steroid-binding β-globulin (SHBG) in apparently healthy men in the Arctic zone of the Russian Federation, taking into account the territory of residence. There were examined 181 men aged 22-60 years, living in the territories of the European and Asian North. The levels of sex hormones, SHBG, and dopamine were determined by the enzyme-linked immunosorbent assay. The inhabitants of the Asian North in comparison with the men of the European North have higher levels of dopamine, luteinizing hormone, progesterone, prolactin, estradiol and SHBG with decreased serum levels of free fractions of testosterone. Reference levels of dopamine in men from the European North are combined with the stimulatory effect of dopamine on LH levels, which may indicate an increase steroidogenesis. The high levels of dopamine in men from the Asian North are combined with increased level of estradiol, which may be related to the effect of dopamine on testosterone aromatization. The separate region with its ecological differences is characterized by the presence of features of compensatory-adaptive reactions of an organism in male representatives on the part of the dopaminergic system and the hypothalamic-pituitary-gonadal axis. The identified features can help in carrying out preventive measures aimed at preserving the male reproductive potential of the inhabitants of the Arctic territories., Competing Interests: The authors declare no conflict of interest.

Positive changes in the society led to an improvement in quality and lifetime; as a result the menopause in women lengthens much longer, in light of this the relevance of studying hormonal changes increases, especially among the representatives of different groups living in the Arctic territories. The study was carried out on 138 women who included nomadic and settled aboriginal and local Caucasoid postmenopausal populations, permanently residing in the Arctic territories of Russia. The greatest difference in the studied blood indicators was shown between the local Caucasoid and aboriginal population. A greater imbalance in the content of dopamine in Aborigines compared with the European population was combined with a higher levels of prolactin, sex hormone binding globulin, antisperm antibodies and with lower concentrations of lutropine, progesterone, total and free testosterone. In the settled aboriginal population compared with nomadic one there were shown the larger proportion of people with low levels of dopamine, lutropine, follitropin and high levels of prolactin, sex hormone binding globulin in the presence of increased number of feedbacks in the hypothalamic-pituitary-gonadal system, which suggested more pronounced reduction of its activity. The evident imbalance of the dopamine content in the aboriginal population was combined with the absence of connections between dopamine level and the parameters of the hypothalamic-pituitary-gonadal system. Positive correlation between the contents of dopamine and lutropin in the European population suggested the stimulating effect of dopamine on the hypothalamic-pituitary-gonadal system. Affected by imbalanced dopamine content the decreased activity of gonadotropic pituitary gland function as well as the peripheral part of the hypothalamic-pituitary-gonadal system was registered in the aboriginal Arctic population in comparison with the local European one, which was more pronounced in the settled aboriginals., Competing Interests: The authors declare no conflict of interest.

Using the methods of radioimmunoassay and enzyme immunoassay there were studied the levels of hormones of the pituitary-thyroid and pituitary-gonadal systems in the postmenopausal women of the European North of the Russian Federation in the second period of mature age, elderly and senile ages. The lower concentrations of total and free fractions of triiodothyronine and total thyroxin, testosterone, dehydroepiandrosterone sulfate, and estradiol were noted in the blood of investigated women in the senile age. Excess levels of thyroid-stimulating hormone were shown in 12,1% of people in the II period of mature age and 17,4% of people in the elderly age. The examined women showed signs of androgenization, manifested by elevated values of luteinizing hormone, testosterone and dehydroepiandrosterone sulfate. The levels of luteinizing hormone exceed the norm in 50% of persons of the second period of mature age, 18,2% of the elderly and 26,1% of the persons of senile age. The concentrations of testosterone and dehydroepiandrosterone sulfate exceed the norms established for the postmenopausal period in 15,4 and 91,7% of persons in the second period of mature age and in 11,4 of 84,2% of the elderly age. The greatest number of correlation interrelations of the studied hormones levels was noted in senile age.

The examination was applied to the groups of nomadic, settled aboriginal and local Caucasian population of the Arctic, permanently residing in the North. The study was carried out in the same period of the year - the period of increasing of duration of daylight hours. The study covered 253 individuals aged from 21 to 50 years. Despite differences in life-style of nomadic and settled aborigines, the similar signs were established consisting in the higher functional activity of hypophyseal section of the "hypophysis - thyroid" system against the background of lower content of auto-antibodies to thyroid peroxidase under increasing of the level of dopamine in blood as compared with local Caucasian population of the Arctic. The variation of analyzed parameters in aboriginal population depending on life-style also is demonstrated. So, nomadic aboriginal population is characterized by higher content in blood of global and free fractions of triiodothyronine, lower index of peripheral conversion of iodothyronines, increasing of level of dopamine and adenosine mono-phosphate. In case of settled aboriginal population increasing of content of global and free thyroxine is typical. In case of nomadic aborigines an expressed dissonance in content of iodothyronines is established: shifting of limits of variations of global and free triiodothyronine aside of higher bounds of standard at shifting of limits of variations of free fractions of thyroxine aside lower bounds of standard. The positive correlation relationships are registered between content of dopamine, thyroid hormones and adenosine mono-phosphate are registered. They are more expressed nomadic aboriginal population., Competing Interests: The authors declare no conflict of interest.

The serum hormone levels were studied among middle and gerontic aged residents of Arkhangelsk by enzyme immunoassay and radioimmunoassay. The significant increase of follicle-stimulating and luteinizing hormones levels in gerontic aged men was recorded in the presence of higher concentrations of these hormones in women. There was a statistical tendency of decrease in the level of testosterone in gerontic aged women compared to middle aged. Regardless of gender the lowering of the dehydroepiandrosterone sulfate content was observed in gerontic aged residents compared to middle aged. The criteria of functional activity reduction of the thyroid gland were a decrease in serum free thyroxine fraction levels in gerontic aged women and low concentrations of common triiodothyronine in middle aged men living in Arkhangelsk. Serum cortisol, insulin, estradiol, growth hormone had no significant age and sex differences in the present groups. The number of correlations was greater among the gerontic aged people in comparison with the middle aged, especially among women.