Pages 383-385 in R. Fortuine et al., eds. Circumpolar Health 96. Proceedings of the Tenth International Congress on Circumpolar Health, Anchorage, Alaska, 1996. Int J Circumpolar Health. 1998;57 Supp 1.
Department of Physiology, University of Oulu, Finland.
Source
Pages 383-385 in R. Fortuine et al., eds. Circumpolar Health 96. Proceedings of the Tenth International Congress on Circumpolar Health, Anchorage, Alaska, 1996. Int J Circumpolar Health. 1998;57 Supp 1.
To evaluate the seasonal influence upon thyroid hormone dynamics, we took blood samples every two months during a period of 14 months from 20 healthy males living in Northern Finland (69-70 degrees N), where the mean daily temperature ranges from a winter minimum of -40 degrees C to a summer maximum of 2 degrees C, while the photoperiod changes from a polar night of 6 days in winter to a polar day of 45 days in summer. The subjects were allowed free choice of diet, exercise, and outdoor exposure. Serum free T3 levels were lower in February than in August (3.9 vs. 4.4 pmol/l, p