Serum Concentrations of the Iodothyronines in Elderly Subjects: Decreased Triiodothyronine (T<sub>3</sub>) and Free T<sub>3</sub> Index

Caplan, Robert H.; Wickus, Gary G.; Glasser, James E.; Davis, Kent D.; Wahner, Heinz W.

doi:10.1111/j.1532-5415.1981.tb02388.x

Cited by 22 publications

(6 citation statements)

References 32 publications

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“…T4 metabolism has been shown in some studies to be reduced in the elderly (17), though this may be related to the increased frequencies of nonthyroidal illnesses and medication intake in this age group. T4 to T3 conversion appears to be normal in healthy elderly individuals (18)(19)(20), though some reduction has been reported (21). While some have recommended reduction in T4 replacement dosage in the elderly (22), the present findings would suggest the opposite.…”

Section: Aging Effect On T4 Absorptioncontrasting

confidence: 44%

Human Thyroxine Absorption: Age Effects and Methodological Analyses

Hays¹,

Nielsen²

1994

Thyroid

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Experience with the use of simultaneous oral and iv radioiodine tracers of thyroxine (T4) to measure T4 absorption was reviewed to determine the effect of advanced age on T4 absorption and to search for acceptable simplifications in the measurement methodology. (1) Age effect: In control subjects, T4 absorption did not differ with age between 21 and 69 years; it averaged 62.8 +/- 13.5% (SD) in subjects over age 70 compared with 69.3 +/- 11.9% in subjects aged 21-69 (p < 0.001). We conclude that, because of this small but significant reduction in T4 absorption efficiency in the elderly, it is especially important to monitor individual response to replacement T4 doses in this age group. (2) Methodology studies: Intrasubject coefficient of variation for T4 absorption in triplicate studies averaged 8.9%, when an identical method was used at weekly intervals (n = 3). When the 3 studies were done by 3 separate methods (sequential po and i.v. 123I-labeled T4, sequential 125I-labeled T4 po and i.v., and simultaneous po and i.v. doses of different tracers), the intrasubject coefficient of variation averaged 9.8% (n = 8). When the absorption calculation used only one serum sample, taken after isotopic equilibrium was achieved at 24 h [the double isotope (eq) method], calculated T4 absorption differed little from that calculated in the same subjects using a full serum time-activity curve and a noncompartmental analysis [the double isotope (AUC) method]. Compared with a compartmental model solution, both methods slightly overestimated T4 absorption. In 4 subjects given i.v. radioiodide as a third tracer at the same time demonstrated that, as long as radioiodide contamination of the T4 tracers is measured and accounted for in the standards, contaminating radioiodide has no clinically significant effect on T4 absorption measurements. When an oral tracer of T4 was considered alone, without an i.v. tracer to correct for T4 metabolism, the estimates of T4 absorption correlated in a curvilinear fashion with T4 absorption as measured by the double isotope method. Except at very low absorption levels, the oral tracer alone is a poor predictor of T4 absorption. We conclude that, when using a double isotope method to measure T4 absorption, it is acceptable to rely on a single serum sample taken at 24 h, a time when isotopic equilibrium between the two tracers has been reached.(ABSTRACT TRUNCATED AT 400 WORDS)

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Section: Aging Effect On T4 Absorptioncontrasting

confidence: 44%

Human Thyroxine Absorption: Age Effects and Methodological Analyses

Hays¹,

Nielsen²

1994

Thyroid

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“…Premenopausal women show mainly positive correlation; in postmenopausal women, negative correlations prevail. These different correlation patterns between pre-and postmenopausal women may be due to the decrease of TSH levels with increasing age, especially after menopause (Knick, 1974;Berthezene, 1979;Baschieri et al, 1982;Rubenstein et al, 1973;Caplan et al, 1981;Bottiglioni et al, 19831, and to the wellknown changes in the amount and distribution of subcutaneous fat tissue after menopause (Knick, 1974;Aloysio et al, 1988;Ley et al, 1992;Dawson-Hughes and Harris, 1992).…”

Section: Discussionmentioning

confidence: 95%

Body dimensions and thyroid hormone levels in premenopausal and postmenopausal women from Austria

Kirchengast

1994

American J Phys Anthropol

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Correlations between thyroid hormone levels and body dimensions were investigated in a group of 124 premenopausal (ages 16-40 years) and 142 postmenopausal (ages 38-61 years) women from Vienna, Austria. Twenty-nine absolute body dimensions and thirteen anthropometric indices were correlated with the serum levels of thyroxine, triiodothyronine, thyroid-stimulating hormone, and thyroid-hormone-binding globulin as well as three hormone ratios (T3/T4, T4/TSH, T3/TSH). All hormones exhibited statistically significant correlations with 24 anthropometric variables and 11 indices. The correlations between thyroxine and triiodothyronine levels and the body measurements were predominantly positive in both proband groups. Higher thyroid hormone levels were associated positively with body dimensions, especially with the amount of subcutaneous fat tissue, in adult females independently of their menstrual status. The direction of the correlations between thyroid-stimulating hormone and body measures as well as anthropometric indices differed between the premenopausal and the postmenopausal women. While in premenopausal women mainly positive correlations between anthropometric characters and the level of thyroid stimulating hormone occur, in postmenopausal women most of these correlations are negative. This is probably due to the decrease of thyroid-stimulating hormone levels with increasing age, as well as with changes in body shape during the climacteric and after the menopause.

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“…Other studies reported also a reduction of fT3 levels 50 . All studies agree, however, that these abnormalities occur in old and older subjects, in the eighth-ninth decades of life 48–50 …”

Section: Discussionmentioning

confidence: 62%

Low-Dose Occupational Exposure to Nickel and Thyroid Hormones

Monti¹,

Giammichele²,

Antuono³

et al. 2022

J Occup Environ Med

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The aim of this study was to evaluate the effects of a low-dose exposure to nickel, as it is present in urban air, on thyroid hormones and on thyrotropin in outdoor workers exposed to urban pollutants. Materials and Methods: A total of 164 outdoor workers were studied and divided by sex and smoking habit. Each worker underwent measurement of urinary nickel and of blood triiodothyronine, L-thyroxine, and thyrotropin levels. The statistical analysis was performed. Results: Statistical analysis shows a significant and positive correlation between urinary nickel and L-thyroxine, both in total sample and in males. Discussion and Conclusion: The study suggests that occupational exposure to a low dose of nickel may affect thyroid function in municipal police workers. These data may provide information on other categories of outdoor workers with similar exposure.

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Serum Concentrations of the Iodothyronines in Elderly Subjects: Decreased Triiodothyronine (T₃) and Free T₃ Index

Cited by 22 publications

References 32 publications

Human Thyroxine Absorption: Age Effects and Methodological Analyses

Human Thyroxine Absorption: Age Effects and Methodological Analyses

Body dimensions and thyroid hormone levels in premenopausal and postmenopausal women from Austria

Low-Dose Occupational Exposure to Nickel and Thyroid Hormones

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Serum Concentrations of the Iodothyronines in Elderly Subjects: Decreased Triiodothyronine (T3) and Free T3 Index

Cited by 22 publications

References 32 publications

Human Thyroxine Absorption: Age Effects and Methodological Analyses

Human Thyroxine Absorption: Age Effects and Methodological Analyses

Body dimensions and thyroid hormone levels in premenopausal and postmenopausal women from Austria

Low-Dose Occupational Exposure to Nickel and Thyroid Hormones

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Product

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Serum Concentrations of the Iodothyronines in Elderly Subjects: Decreased Triiodothyronine (T₃) and Free T₃ Index