Thyroid hormone status and nutrient intake in the free-living elderly. Interest of reverse triiodothyronine assessment

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Abstract
Goichot B, Schlienger JL, Grunenberger F, Pradignac A, Sapin R. Thyroid hormone status and nutrient intake in the free-living elderly. Interest of reverse triiodothyronine assessment. Eur J Endocrinol 1994; 130:244–52. ISSN 0804–4643 Fasting or hypocaloric diets are established methods of inducing low triiodothyronine (T3) levels that resemble the sick euthyroid syndrome in adults, but little is known on the mechanisms of this syndrome in the elderly. Decreasing T3 does not seem to be an unavoidable consequence of ageing, but the role of illness or other factors in this decline remains unclear. The aim of this work was to study the influence of nutritional factors on thyroid hormone levels in free-living elderly subjects. A 3-day dietary survey was conducted in 440 randomized subjects aged between 65 and 96. Cholesterol, apoproteins, prealbumin, hemoglobin, thyrotropin-free thyroxine (FT4), FT3 and reverse T3 (rT3) were assayed in each subject. Only 11 subjects had low FT3 levels, and they also had low levels of cholesterol, prealbumin and hemoglobin and a lower Folstein score compared to the rest of the population. Twenty-one subjects had isolated elevated rT3 levels, they were older and had significantly lower energy and fat intakes than the rest of the population. There was a clear reduction in FT3 levels and an increase in rT3 levels with age, although in the normal ranges, which occurred despite maintenance of a high-energy intake even in the oldest group. The FT3 level was lower in the subjects with poor health status, whereas high rT3 levels were associated with low energy intake in men. Stepwise regression showed that hemoglobin, age and prealbumin were the best predictors of FT3 levels, whereas age and energy intake were the main predictors of rT3 levels. Our results confirm the low prevalence of the low T3 syndrome in healthy elderly persons, and demonstrate the existence of another group of elderly subjects with isolated elevated rT3 levels. Whereas a low FT3 level seems to be associated with illness, rT3 is clearly associated with a low energy intake. Other studies are necessary to appreciate the specificity of this association and the usefulness of rT3 as an indication of nutrient intake. JL Schlienger, Service de Médecine Interne, CHU Hautepierre, avenue Molière, 67098 Strasbourg Cedex, France

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