# Suppression and Recovery of the Murine Hypothalamic-Pituitary-Adrenal Axis after Exogenous Glucocorticoid Treatment

> **NIH NIH F32** · BOSTON CHILDREN'S HOSPITAL · 2021 · $75,330

## Abstract

PROJECT SUMMARY/ABSTRACT:
Chronic, supraphysiologic glucocorticoid exposure leads to suppression of the hypothalamic-pituitary-adrenal (HPA)
axis that can persist for months after steroids are withdrawn, leaving individuals vulnerable to life-threatening
adrenal crises. Clinical studies in humans suggest that HPA axis dysfunction after withdrawal of long-term steroids
is mediated first by hypothalamic-pituitary dysfunction followed by delayed adrenocortical recovery despite
appropriate, compensatory ACTH stimulation. While the mammalian HPA axis is highly conserved, robust animal
models of steroid-induced suppression and recovery are lacking. This has limited our understanding of the
mechanisms driving protracted but reversible HPA axis dysfunction after withdrawal of long-term glucocorticoids,
which are likely both centrally and adrenally mediated and distinct from simple negative feedback. This study seeks
to characterize the relationship between the duration of exogenous, supraphysiologic glucocorticoid exposure and
time to functional HPA axis recovery as well as the molecular changes driving these processes at the level of the
hypothalamus, pituitary, and adrenal glands. We will treat adult, male C57BL/6J mice (n=5/cohort) for 1, 8, or 24
weeks with either vehicle (DN) or dexamethasone (DEX; 10 mcg/day=~35 mg hydrocortisone equivalent/m2/day) via
drinking water. We will then perform weekly assessments of basal (circadian peak and nadir) and stress-induced
ACTH and CORT secretion from the time of steroid withdrawal until functional recovery is documented, defined as
the timepoint at which there are no significant differences between these ACTH and CORT levels vs. those of DN
animals by ANOVA with Dunnett’s multiple comparisons test. To measure stress-induced secretion, animals will
undergo both insulin-induced hypoglycemia and Cosyntropin stimulation testing to assess how the axis responds to
a potent, physiologic stressor as well as adrenocortical sensitivity to a common stimulus. Animals from each of
these timepoints will undergo necroscopy after the final functional assessment, from which we will generate
hypothalamic, pituitary, and adrenal sections for quantification of Crh, Pomc, and Cyp11b1 mRNA expression,
respectively. We will next assess whether steroid-induced suppression and recovery are mediated by sequential
apoptosis and mitosis of each of these cell types. To do this, we will first perform TUNEL staining followed by
immunohistochemistry for either 1) activated caspase-3 or 2) Ki67 co-localized with a) CRH, b) POMC, or c) steroid
11β-hydroxylase in adrenal, pituitary, or hypothalamic sections. Finally, we will document zona Fasiculata
regeneration from zona Glomerulosa precursors in DEX-treated, aldosterone synthase (AS)-Cre/mTmG (AS+/Cre : :
R26R+/mTmG) mice, with fluorescent microscopy of adrenals at the time of steroid withdrawal, HPA axis recovery, and
several intermediate timepoints defined by the prior experiments. These s...

## Key facts

- **NIH application ID:** 10388563
- **Project number:** 1F32DK131795-01
- **Recipient organization:** BOSTON CHILDREN'S HOSPITAL
- **Principal Investigator:** Lindsey Sara Gaston
- **Activity code:** F32 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $75,330
- **Award type:** 1
- **Project period:** 2022-07-01 → 2024-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10388563

## Citation

> US National Institutes of Health, RePORTER application 10388563, Suppression and Recovery of the Murine Hypothalamic-Pituitary-Adrenal Axis after Exogenous Glucocorticoid Treatment (1F32DK131795-01). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10388563. Licensed CC0.

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