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Age and cortisol suppression by dexamethasone in normal subjects
1Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas.
Journal of Psychiatric Research
|January 1, 1989
Summary
The dexamethasone suppression test (DST) may be less reliable in older adults. Inadequate plasma dexamethasone levels, particularly in elders, can invalidate DST results, necessitating concurrent plasma dexamethasone level assays.
Area of Science:
- Endocrinology
- Geriatric Medicine
- Clinical Chemistry
Background:
- The dexamethasone suppression test (DST) assesses the hypothalamic-pituitary-adrenal (HPA) axis's negative feedback.
- Adequate plasma dexamethasone (DEX) levels are crucial for DST validity.
Purpose of the Study:
- To determine the required 0800 h plasma DEX levels for a valid DST.
- To investigate the frequency of DST nonsuppression and its relation to plasma DEX levels in healthy adults across a wide age range.
Main Methods:
- A study involving 60 healthy volunteers aged 19-88 years.
- Measurement of 0800 h plasma DEX levels in all participants.
- Analysis of DST nonsuppression rates and correlation with plasma DEX concentrations.
Main Results:
- Nonsuppression was rare (5%) in the overall cohort.
- A plasma DEX level exceeding 220 ng/dl at 0800 h was confirmed as necessary for DST validity.
- Inadequate DEX levels were observed in three subjects, all over 50 years old.
- Two of the three DST nonsuppressors had inadequate DEX concentrations.
Conclusions:
- DST may be less reliable in older adults due to inadequate plasma DEX concentrations.
- Concomitant assay of plasma DEX levels alongside DST is recommended in elderly individuals to ensure test validity.