1. Iodothyronine 5'-deiodinase, which is mainly responsible for peripheral triiodothyronine (T-3) production, has recently been demonstrated to be a selenium-containing enzyme. In the elderly, reduced peripheral conversion of thyroxine (T-4) to T-3 and overt hypothyroidism are frequently observed. 2. We measured serum selenium and erythrocyte glutathione peroxidase (as indices of selenium status), thyroid hormones and thyroid-stimulating hormone in 109 healthy euthyroid subjects (52 women, 57 men), carefully selected to exclude abnormally low thyroid hormone levels induced by acute or chronic diseases or calorie restriction. The subjects were subdivided into three age groups. To avoid conditions of undernutrition or malnutrition, dietary records were obtained for a sample of 24 subjects, randomly selected and representative of the whole population for age an sex. 3. In order to properly assess the influence of selenium status on iodothyronine 5'-deiodinase type I activity, a double-blind placebo-controlled trial was also carried out on 36 elderly subjects, resident at a privately owned nursing home. 4. In the free-living population, a progressive reduction of the T-3/T-4 ratio (due to increased T-4 levels) and of selenium and erythrocyte glutathione peroxidase activity was observed with advancing age. A highly significant linear correlation between T-4, T-3/T-4 and selenium was observed in the population as a whole (for T-4, R = - 0.312, P lt 0.002; for T-3/T-4 ratio, R=0.32, P lt 0.01) and in older subjects (for T-4, R=-0.40, P lt 0.05; for T-3/T-4 ratio, R=0.54, P lt 0.002). 5. The main result of the double-blind placebo controlled trial was a significant improvement of selenium indices and a decrease in the T-4 level in selenium-treated subjects; serum selenium, erythrocyte glutathione peroxidase activity and thyroid hormones did not change in placebo-treated subjects. 6. We concluded that selenium status influences thyroid hormones in the elderly, mainly modulating T-4 levels.
Low selenium status in the elderly influences thyroid hormones
OLIVIERI, Oliviero;GIRELLI, Domenico;STANZIAL, Annamaria;CORROCHER, Roberto
1995-01-01
Abstract
1. Iodothyronine 5'-deiodinase, which is mainly responsible for peripheral triiodothyronine (T-3) production, has recently been demonstrated to be a selenium-containing enzyme. In the elderly, reduced peripheral conversion of thyroxine (T-4) to T-3 and overt hypothyroidism are frequently observed. 2. We measured serum selenium and erythrocyte glutathione peroxidase (as indices of selenium status), thyroid hormones and thyroid-stimulating hormone in 109 healthy euthyroid subjects (52 women, 57 men), carefully selected to exclude abnormally low thyroid hormone levels induced by acute or chronic diseases or calorie restriction. The subjects were subdivided into three age groups. To avoid conditions of undernutrition or malnutrition, dietary records were obtained for a sample of 24 subjects, randomly selected and representative of the whole population for age an sex. 3. In order to properly assess the influence of selenium status on iodothyronine 5'-deiodinase type I activity, a double-blind placebo-controlled trial was also carried out on 36 elderly subjects, resident at a privately owned nursing home. 4. In the free-living population, a progressive reduction of the T-3/T-4 ratio (due to increased T-4 levels) and of selenium and erythrocyte glutathione peroxidase activity was observed with advancing age. A highly significant linear correlation between T-4, T-3/T-4 and selenium was observed in the population as a whole (for T-4, R = - 0.312, P lt 0.002; for T-3/T-4 ratio, R=0.32, P lt 0.01) and in older subjects (for T-4, R=-0.40, P lt 0.05; for T-3/T-4 ratio, R=0.54, P lt 0.002). 5. The main result of the double-blind placebo controlled trial was a significant improvement of selenium indices and a decrease in the T-4 level in selenium-treated subjects; serum selenium, erythrocyte glutathione peroxidase activity and thyroid hormones did not change in placebo-treated subjects. 6. We concluded that selenium status influences thyroid hormones in the elderly, mainly modulating T-4 levels.
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