MELATONIN AND THYROID HORMONES IN THE COLD ANDIN DARKNESS, ACTA UNIVERSITATIS OULUENSIS D Medica 1045

The purpose of the study was to examine the cold-induced effects on pineal and thyroid hormones,as well as the associations of these hormones with psychological performance and to determinehow psychological performance could be affected by demographic, anthropometric, physiologicalor biochemical measures during cold acclimatisation. The feasibility of urinary melatonin (MT),rather than 6-sulphatoxymelatonin (aMT6s), as an indicator of MT secretion was also examined.\n In the laboratory study, seasonal cold acclimatisation, its effects on hormones and theirassociations with mood and cognition were assessed in 15 young urban subjects exposed to coldin winter or summer in bright or dim light. In the field study, the associations of mood andcognition with demographic, anthropometric, physiological and biochemical measures weredetermined in healthy, euthyroid subjects (n=133) in Antarctica in the beginning and at the endof summer and winter seasons.\nIn both seasons, simple task performance was consistently impaired in the cold in experimentaland field conditions. In complex tasks, negative, positive and mixed effects were observed. In theexperimental study, serum MT and thyroid hormone levels were positively associated with mood.MT was negatively associated with simple task performance. Free triiodothyronine (T3) andthyrotropin (TSH) had mixed effects on simple task performance. TSH was positively associatedwith complex task performance. In the field study, higher age was associated with impairedcognition, especially in complex task performance. Total T3 was positively associated with moodand total thyroxine (T4) with complex task accuracy. Both urinary MT and aMT6s were goodindicators of MT secretion, but the variation was smaller for MT.\nIn conclusion, the associations of serum MT, TSH and thyroid hormone levels with mood andcognition found in experimental and field conditions are consistent with the psychologicalchanges associated with the onset and consequent stages of the previously established polar T3syndrome. In the field study, cognition and mood were associated with subject’s age and gender,which seemed to affect the physiological changes during acclimatisation to cold and darkness inAntarctica.

ISBN-10:
978-951-42-6120-6
Kieli:
eng.
Sivumäärä:
158 s.
Tekijät:
Pääkkönen Tiina
Tuotekoodi 013946
20,00 €