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Cited by 96Thyroid Disorders and TreatmentsHormonal and reproductive studiesGrowth Hormone and Insulin-like Growth Factors

Pituitary-Thyroid Hormone Economy in Healthy Aging Men: Basal Indices of Thyroid Function and Thyrotropin Responses to Constant Infusions of Thyrotropin Releasing Hormone*

HARMAN, S. MITCHELL, WEHMANN, ROBERT E., BLACKMAN, MARC R.·1984·The Journal of Clinical Endocrinology & Metabolism
DOI 10.1210/jcem-58-2-320
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Abstract

In order to assess the effects of aging, as distinct from those of thyroid disease or extrathyroidal illness, on certain indices of thyroid function, we studied 74 healthy, ambulatory men recruited from the Baltimore Longitudinal Study on Aging. We determined basal serum values of T4, T3, rT3, thyroxine-binding globulin (TBG), and T3 resin uptake (T3RU) and calculated the free T4 index (FT4I = T4 X T3RU/100), free T3 index (FT3I = T3 X T3RU/100), and T4/TBG ratio for each subject. We used an ultrasensitive RIA to measure variations in basal concentrations of TSH within the normal range. We then infused TRH at a constant rate (0.4 microgram/min iv) for 240 min into 63 of the same men; serum samples, collected at 15-min intervals during the infusion, were analyzed for TSH by routine RIA. Subjects were divided into 3 groups according to age; A (n = 26, mean age = 39.4), B (n = 23, mean age = 60.0), and C (n = 25, mean age = 79.6). Analysis of variance with Duncan's multiple range test and regression analysis were used to evaluate data. There was no significant (P greater than 0.05) variation with age of basal serum values of T4, TBG, or T3RU. Comparison of groups A and C showed significant decreases of mean values of serum T3 (-11%, P less than 0.05), FT3I (-13%, P = 0.02), FT4I (-11%, P less than 0.01), and T4/TBG ratio (-12%, P less than 0.01) and an increase in serum TSH (+38%, P less than 0.05). For these variables, the mean values for group B were intermediate between, but not significantly different from, those of A and C. Regression analysis showed significant correlations of age with T3, FT3I, FT4I, T4/TBG, and TSH at P levels similar to those obtained by Duncan's test. No elderly individual exhibited a baseline elevation of TSH (greater than 7 microU/ml) or depression of T4 (less than 5 micrograms/dl), suggesting that primary hypothyroidism was not present in our old group. The basal TSH concentration did not correlate significantly with any index of thyroid function except with FT3I in group C (r = -0.43, P less than 0.05). In all age groups the TSH responses to TRH exhibited a biphasic pattern with early and late peaks.(ABSTRACT TRUNCATED AT 400 WORDS)

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Authors
HARMAN, S. M., WEHMANN, R. E., & BLACKMAN, M. R.
Affiliations
National Institutes of Health (US)
ORCID
HARMAN, S. MITCHELL
Venue
The Journal of Clinical Endocrinology & Metabolism
Publisher
The Endocrine Society
Published
1984-02
Volume
58
Issue
2
Pages
320-326
ISSN
  • 0021-972X (ISSN-L)
  • 1945-7197
DOI
10.1210/jcem-58-2-320
OpenAlex
W2001026479
Cited by
96
References
22
Citations by year
2020: 1 · 2018: 2 · 2017: 1 · 2016: 6 · 2015: 2 · 2012: 2
FWCI
4.42
Type
journal article
Language
en
Open access
closed
Locations
  • The Journal of Clinical Endocrinology & Metabolism (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Thyroid Disorders and Treatments
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Hormonal and reproductive studies
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Growth Hormone and Insulin-like Growth Factors
Keywords
healthy aging, thyroid function, thyroid-stimulating hormone, thyrotropin-releasing hormone, TSH response, free T4 index, thyroxine-binding globulin, T3 resin uptake, age-related changes, older men, thyroxine
MeSH terms
Adult, Aged, Aging, Animals, Cats, Humans, Male, Middle Aged, Pituitary Function Tests, Pituitary Gland, Sex Factors, Thyroid Function Tests, Thyroid Gland, Thyrotropin, Thyrotropin-Releasing Hormone

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