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International Journal of Endocrinology
Volume 2019, Article ID 2762978, 9 pages
Research Article

Relation of Different Components of Climate with Human Pituitary-Thyroid Axis and FT3/FT4 Ratio: A Study on Euthyroid and SCH Subjects in Two Different Seasons

1Department of Medicine, College of Medicine, University of Sulaimani, Sulaymaniyah 46001, Iraq
2Physiology Department, College of Medicine, University of Sulaimani, Sulaymaniyah 46001, Iraq

Correspondence should be addressed to Darya S. Abdulateef; qi.ude.lusvinu@feetaludba.ayrad

Received 8 July 2018; Accepted 25 November 2018; Published 16 January 2019

Academic Editor: Claudio Casella

Copyright © 2019 Taha O. Mahwi and Darya S. Abdulateef. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Background. Various changes in thyroid hormones (TH) and thyroid-stimulating hormone (TSH) level were observed in different seasons among euthyroid and hypothyroid subjects living in areas with an extreme temperature difference between summer and winter. Objectives. This study aims at finding the effect of temperate climate on the seasonal variations of TSH and TH in euthyroid and subclinical hypothyroidism (SCH) subjects and at evaluating if the test season has an effect on the number of subjects diagnosed as SCH. It basically focuses on the relation of different components of climate with TH and TSH. Method. In a prospective study on 152 healthy (euthyroid) volunteers and 25 SCH subjects, the serum hormone levels (TSH, FT4, and FT3) were measured in both the summer and winter seasons and correlated with all the climate components using Pearson’s correlation coefficient. The effect of duration of outdoor exposure on hormone levels was compared using a paired sample -test (). Results. Small but statistically significant increased FT3 level and decreased FT4 level were observed during the winter season in euthyroid and SCH subjects, respectively. There was a significant negative correlation between FT3 and FT3/FT4 ratio with temperature and sunshine duration and a positive correlation with humidity and atmospheric pressure. A positive correlation was found between FT4 and sunshine duration. Conclusion. The climate components contributed to the slight variance in hormone levels in different seasons, and the effect was mostly on peripheral conversion of FT4 to FT3 rather than the pituitary-thyroid axis leading to slightly higher FT3 in winter. Seasonal variation does not affect the diagnosis of SCH cases.