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Letters to the Editor Selenium, Thyroid Hormones, Mood, and Behaviour Dear Editor: It has been well known for many years that both hypo- and hyperthyroidism may cause various psychiatric symptoms (1). Both hypo- and hyperthyroidism may be associated with changes in mood, behaviour, and cognitive function. There is substantial evidence that small changes in thyroid function may be biologically meaningful and affect mood and behaviour (2). Selenium is required for appropriate thyroid hormone synthesis, activation, and metabolism (3,4). Among all organs, the human thyroid gland has the highest selenium content per gram of tissue. Low selenium status may compromise thyroid hormone metabolism. Low selenium status can be a result of low selenium intake (4). Selenium concentration in blood and tissue can also be affected in patients with chronic renal failure treated by hemodialysis or by chronic peritoneal dialysis (5). Considerable evidence suggests that selenium deprivation leads to depressed mood, and high dietary or supplementary selenium seems to improve mood (4,6). Several research groups have found that low selenium status is associated with a significantly increased incidence of depression, anxiety, confusion, and hostility (4,6). Low plasma selenium concentrations in the elderly have been significantly associated with senility and cognitive decline (7). Therefore, it is reasonable to suggest that the effect of selenium status on mood, behaviour, and cognition may be partly mediated by changes in thyroid function induced by selenium deficiency or selenium supplementation. Iodine prophylaxis was initiated during the 1920s. Future studies may answer the question whether, in addition to iodine prophylaxis, we also need selenium supplementation to optimize the function of the thyroid axis.
1. Haggerty JJ, Garbutt JC, Evans DL, Golden RN, Pedersen C, Simon JS, and others. Subclinical hypothyroidism: A review of neuropsychiatric aspects. Int J Psychiatry Med 1990;20:193–208. 2. Sher L, Rosenthal NE, Wehr TA. Free thyroxine and thyroid-stimulating hormone levels in patients with seasonal affective disorder and matched controls. J Affect Disord 1999;56:195–9. 3. Koehrle J. The trace element selenium and the thyroid gland. Biochimie 1999;81:527–33. 4. Rayman MP. The importance of selenium to human health. Lancet 2000;356:233–41. 5. Zima T, Mestek O, Nemecek K, Bartova V, Fialova J, Tesar V, Suchanek M. Trace elements in hemodialysis and continuous ambulatory peritoneal dialysis patients. Blood Purif 1998;16:253–60. 6. Benton D, Cook R. Selenium supplementation improves mood in a double-blind crossover trial. Biol Psychiatry 1991;29:1092–8. 7. Berr C, Balansard B, Arnaud J, Roussel AM, Alperovitch A. Cognitive decline is associated with systemic oxidative stress—the EVA study. J Am Geriat Soc 2000;48:1285–91. Leo Sher, MD
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