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.
RCT Entities:
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.
Authors: C Strewe; D Moser; J-I Buchheim; H-C Gunga; A Stahn; B E Crucian; B Fiedel; H Bauer; P Gössmann-Lang; D Thieme; E Kohlberg; A Choukèr; M Feuerecker Journal: Biol Sex Differ Date: 2019-04-16 Impact factor: 5.027
Authors: Tracey L Sletten; Jason P Sullivan; Josephine Arendt; Lawrence A Palinkas; Laura K Barger; Lloyd Fletcher; Malcolm Arnold; Jan Wallace; Clive Strauss; Richard J S Baker; Kate Kloza; David J Kennaway; Shantha M W Rajaratnam; Jeff Ayton; Steven W Lockley Journal: J Pineal Res Date: 2022-07-25 Impact factor: 12.081