Seasonal changes in the pituitary - thyroid system in children of the Arctic region of Yakutia

A Systematic Review and Meta-Analysis of Free Triiodothyronine (FT3) Levels in Humans Depending on Seasonal Air Temperature Changes: Is the Variation in FT3 Levels Related to Nonshivering Thermogenesis?

“…Thus, our proposed concept that active BAT in adults in all regions of the world can affect blood T3 levels depending on the air temperature in winter (regions with “Cold winter” and “Warm winter”) may explain the contradictory results about seasonal variations of this hormone [ 10 , 12 , 15 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ] and it is consistent with the previously obtained results on the seasonal dynamics of TSH levels [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ].…”

“…However, with strong and prolonged cold exposure, the BAT will consume a lot of T3, and it can take T3 directly from the blood. Therefore, in regions with “Cold winters”, it is possible to observe a tendency to decrease T3 levels in the blood in winter compared to summer and an inverse tendency for TSH levels [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. In regions with “Warm winters”, a similar imbalance also occurs in response to moderate cold exposure.…”

“…To date, there are many studies devoted to the seasonal fluctuation of pituitary-thyroid hormones in adults. Multiple studies have shown that TSH levels were higher in winter than during other seasons in both euthyroid individuals and patients with various thyroid diseases [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ]. In addition, the studies using large-scale data on TSH levels have also shown a seasonal dependence of TSH levels, with a peak in the winter [ 19 , 20 ].…”