A randomized placebo‐controlled clinical trial of the effectiveness of thyroxine and triiodothyronine and short‐term exposure to bright light in prevention of decrements in cognitive performance and mood during prolonged Antarctic residence
Summary Objective We examined the effects of a combined levothyroxine/liothyronine supplement and exposure to bright (10,000 lux) light in euthyroid men and women who spent the austral summer ( n = 43) and/or winter ( n = 42) in Antarctica. Methods Subjects were randomized to receive 64 nmol of levo...
| Published in: | Clinical Endocrinology |
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| Main Authors: | , , , , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Wiley
2010
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| Subjects: | |
| Online Access: | http://dx.doi.org/10.1111/j.1365-2265.2009.03669.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1365-2265.2009.03669.x https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2265.2009.03669.x |
| Summary: | Summary Objective We examined the effects of a combined levothyroxine/liothyronine supplement and exposure to bright (10,000 lux) light in euthyroid men and women who spent the austral summer ( n = 43) and/or winter ( n = 42) in Antarctica. Methods Subjects were randomized to receive 64 nmol of levothyroxine and 16 nmol of liothyronine supplement or a placebo capsule for 93·2 ± 3·0 days in summer and/or 149·5 ± 2·2 days in winter. Subjects were further randomized to receive 10,000 lux bright white light or 50 lux dim red light for 14 days at the end of summer and/or winter. Cognitive performance and mood were assessed using the Automatic Neuropsychological Assessment Metric – Isolated and Confined Environments. Results In winter, bright light exposure was associated with a significantly greater reduction in TSH and anger ( P < 0·05), a significantly greater increase in fT 3 ( P < 0·05), and a significantly smaller increase in depressive symptoms ( P < 0·001), when compared with dim light. The T4/T3 supplement also led to a significantly greater reduction in TSH ( P < 0·05), but a greater reduction in cognitive task efficiency ( P < 0·05) as well, when compared with placebo. Conclusion Administration of bright light leads to a significant reduction in serum TSH and prevents increases in anger and depressive symptoms in winter. However, these associations were not observed in summer, suggesting a seasonal influence of photoperiod over temperature upon this intervention in the polar environment. |
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