Lab Reference Library / ACTH (Adrenocorticotropic Hormone)
Advanced & Specialty
ACTH (Adrenocorticotropic Hormone)
ACTH · Adrenocorticotropic Hormone · CorticotropinReference range, optimal functional medicine levels, and why ACTH is the pituitary signal that drives cortisol production, how it distinguishes primary from secondary adrenal insufficiency, and why ACTH testing is essential for evaluating HPA axis function beyond a single cortisol measurement.
HPA Axis MarkerSpecialty Testing
Standard Range7 to 63 pg/mL
FM Optimal (AM)15 to 40 pg/mL
Low (Pituitary)Below 7 pg/mL
Unitspg/mL
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Category: Advanced & Specialty | Also known as: Adrenocorticotropic Hormone, Corticotropin | Sample: Plasma (EDTA tube; ice immediately; process within 15 minutes; morning draw required)
1. What This Test Measures
ACTH (adrenocorticotropic hormone) is a 39-amino acid peptide hormone produced by corticotroph cells in the anterior pituitary gland. Its primary function is to stimulate the adrenal cortex to produce cortisol, the body's principal glucocorticoid. ACTH is the central regulatory hormone of the HPA (hypothalamic-pituitary-adrenal) axis, the cascade that governs the stress response, energy mobilization, immune modulation, and circadian rhythmicity.
CRH (corticotropin-releasing hormone) from the hypothalamus stimulates ACTH release. ACTH then travels via the bloodstream to the adrenal cortex where it binds MC2R receptors, stimulating steroidogenesis and cortisol production. Cortisol in turn feeds back negatively to the hypothalamus and pituitary to suppress further CRH and ACTH release, completing the regulatory loop. Understanding this axis is essential to interpreting ACTH: an elevated ACTH with elevated cortisol points to a pituitary or ectopic source; an elevated ACTH with low cortisol points to primary adrenal failure (Addison's disease); a low ACTH with low cortisol points to central (pituitary or hypothalamic) insufficiency.
ACTH is extraordinarily labile: it degrades rapidly at room temperature and is critically affected by pre-analytical handling. Samples must be collected in pre-chilled EDTA tubes, immediately placed on ice, and processed within 15 minutes. Morning collection (7 to 9 AM) is required to capture the physiological ACTH-cortisol peak. Errors in handling produce falsely low results that can mimic central adrenal insufficiency.
2. Optimal Range and Clinical Thresholds
| ACTH (Morning) | Interpretation |
|---|---|
| 10 to 35 pg/mL | Optimal: appropriate morning HPA axis drive; normal circadian rhythm |
| 35 to 46 pg/mL | High-normal: evaluate for early HPA activation, chronic stress, or subclinical pituitary lesion |
| Above 46 pg/mL | Elevated: primary adrenal insufficiency, Cushing's disease (pituitary), or ectopic ACTH syndrome; evaluate with cortisol and imaging |
| Below 10 pg/mL | Low: central adrenal insufficiency (pituitary or hypothalamic origin); evaluate with stimulation testing |
Always interpret ACTH paired with simultaneous morning cortisol. The ACTH/cortisol relationship is more diagnostically informative than either marker alone. Reference ranges vary slightly by laboratory; clinical interpretation depends on pattern, not absolute value alone.
3. The HPA Axis: Pattern Interpretation
| ACTH | Cortisol | Pattern | Diagnosis to Evaluate |
|---|---|---|---|
| High | High | Both elevated together | Cushing's disease (pituitary ACTH excess) or ectopic ACTH syndrome; 24-hr urine cortisol and MRI pituitary |
| High | Low | High drive, low response | Primary adrenal insufficiency (Addison's disease); adrenal gland cannot respond to ACTH signal |
| Low | Low | Both suppressed | Central adrenal insufficiency; pituitary or hypothalamic failure; exogenous glucocorticoid suppression |
| Low | High | Cortisol elevated despite low drive | Exogenous steroid use; adrenal adenoma producing cortisol autonomously; Cushing's syndrome (adrenal) |
| Normal | Low | Inadequate cortisol for ACTH drive | Early or partial adrenal insufficiency; stimulation testing (cosyntropin) required |
4. HPA Dysregulation in Functional Medicine
Beyond the structural diagnoses above, ACTH assessment is increasingly used in functional medicine to evaluate HPA axis dysregulation from chronic physiological and psychological stress. Prolonged HPA activation from trauma, sleep deprivation, inflammatory illness, or overtraining can alter ACTH secretion patterns in ways that produce significant symptoms without reaching the threshold of clinical Addison's disease or Cushing's syndrome.
- HPA hyperactivation (elevated morning ACTH with elevated cortisol): chronic stress state; associated with anxiety, insomnia, visceral adiposity, immune suppression, reduced HRV, and accelerated metabolic aging; primary intervention is stress reduction, sleep restoration, and adaptogenic support
- HPA hypoactivation (low-normal ACTH with low-normal cortisol): sometimes called adrenal fatigue in functional medicine literature; reflects central attenuation of HPA axis output from prolonged stress or burnout; symptoms include profound fatigue, poor stress resilience, hypotension, salt craving, and inflammatory flares
- Flattened diurnal rhythm: ACTH and cortisol should be highest in the morning and lowest at midnight; flattening of this rhythm (elevated evening cortisol, reduced morning peak) is associated with poor sleep quality, depression, metabolic syndrome, and impaired immune function
5. Pre-Analytical Requirements
ACTH sample handling is critical. ACTH is the most pre-analytically sensitive hormone in routine clinical testing. Failures in handling produce falsely low results that can lead to unnecessary workup for central adrenal insufficiency.
Requirements: (1) pre-chill EDTA tubes on ice before the draw; (2) draw blood into chilled tubes; (3) immediately return to ice; (4) centrifuge within 15 minutes of collection; (5) freeze plasma promptly; (6) morning collection between 7 and 9 AM; (7) patient should be resting, not acutely ill, and not on exogenous glucocorticoids for at least 24 hours if possible. Even a 30-minute delay at room temperature can reduce measured ACTH by 30 to 50%.
6. How to Support Healthy HPA Axis Function
Lifestyle Foundations
- Sleep restoration: HPA axis circadian rhythm is entrained by sleep; 7 to 9 hours of consistent, dark, cool sleep is the single most impactful HPA intervention; sleep deprivation raises ACTH and cortisol and disrupts diurnal rhythm within days
- Perceived stress reduction: cognitive behavioral therapy, mindfulness meditation, and consistent social connection reduce CRH drive and normalize HPA axis tone over 8 to 12 weeks
- Exercise calibration: moderate aerobic exercise reduces basal HPA activation; overtraining (high-intensity exercise without adequate recovery) chronically elevates ACTH and cortisol
- Consistent meal timing: irregular eating disrupts circadian HPA signaling; consistent meal timing at the same time daily reinforces diurnal ACTH rhythm
Nutritional Support
- Vitamin C (1 to 3g daily): highest concentration in the adrenal cortex; supports steroidogenesis and adrenal recovery; depleted by chronic stress
- Pantothenic acid (B5, 500 to 1,000mg daily): rate-limiting cofactor in adrenal steroidogenesis; supports cortisol production capacity
- Magnesium glycinate (300 to 600mg daily): inhibits ACTH release from the pituitary at the CRH-ACTH interface; most depleted mineral in chronic stress states
- Phosphatidylserine (400 to 800mg daily): documented to reduce ACTH and cortisol response to acute psychological stress in randomized trials; membrane phospholipid that modulates HPA feedback sensitivity
Adaptogenic and Clinical Support
- Ashwagandha (KSM-66, 300 to 600mg daily): most evidence-based adaptogen for HPA axis modulation; reduces ACTH and cortisol in stressed individuals in multiple RCTs; normalizes HPA tone without suppressing it below baseline
- Rhodiola rosea (200 to 400mg daily): reduces fatigue and HPA hyperactivation in clinical trials; most useful for adrenal hyperstimulation pattern
- DHEA assessment: DHEA is co-regulated with cortisol by ACTH; a falling DHEA/cortisol ratio despite elevated ACTH suggests adrenal reserve depletion and warrants DHEA-S evaluation
- Bioidentical cortisol (hydrocortisone) in documented central adrenal insufficiency: requires endocrinology involvement; dose carefully to avoid suppression of residual axis function
7. Related Lab Tests
CortisolEssential Paired Marker with ACTH
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DHEA-SAdrenal Androgen Reserve
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IGF-1Pituitary Growth Axis Companion
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TSHHPA-HPT Axis Interaction
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Fasting InsulinCortisol-Driven Insulin Resistance
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8. Clinical Perspective
Clinical Perspective
ACTH is the hormone that tells me whether the HPA axis problem I am looking at is coming from the pituitary or the adrenal gland, and that distinction determines everything about how I manage it. When a patient presents with profound fatigue, hypotension, and salt craving, and their morning cortisol is 5 mcg/dL, the ACTH tells me whether their adrenal gland is failing to respond to a normal signal or whether the signal itself is inadequate. A high ACTH with low cortisol is Addison's disease until proven otherwise and goes straight to endocrinology. A low ACTH with low cortisol in a patient on prednisone for three years is a different conversation entirely. In functional medicine practice, I also use ACTH to confirm the HPA hyperactivation pattern I see clinically in burned-out, high-achieving patients who sleep four hours a night, train twice a day, and wonder why they cannot lose weight. That pattern has a biology, and ACTH makes it measurable.
Brian Lamkin, DO | Founder, The Lamkin Clinic | Edmond, Oklahoma
9. Frequently Asked Questions
What does elevated ACTH mean?
Elevated morning ACTH indicates that the pituitary is sending a strong stimulatory signal to the adrenal glands. When paired with elevated cortisol, this pattern suggests Cushing's disease (pituitary ACTH overproduction) or ectopic ACTH syndrome from a non-pituitary tumor. When paired with low cortisol, elevated ACTH indicates primary adrenal insufficiency (Addison's disease), where the adrenal gland cannot respond adequately to the pituitary signal.
What does low ACTH mean?
Low ACTH indicates reduced pituitary drive to the adrenal glands. When paired with low cortisol, this confirms central adrenal insufficiency from pituitary or hypothalamic failure. Common causes include prior pituitary surgery, radiation, apoplexy, or prolonged exogenous glucocorticoid use suppressing the axis. This pattern requires cosyntropin stimulation testing to assess adrenal reserve and endocrinology evaluation.
Why must ACTH be collected in the morning?
ACTH and cortisol follow a strong circadian rhythm, peaking between 6 and 9 AM and falling to their lowest levels around midnight. Morning collection captures the peak of the physiological ACTH-cortisol axis and allows comparison to established reference ranges. Afternoon or evening draws will produce falsely low results that do not reflect baseline axis function.
Why is ACTH sample handling so critical?
ACTH is a peptide hormone that degrades extremely rapidly at room temperature due to plasma peptidases. Even a 30-minute delay in processing can reduce measured ACTH by 30 to 50%, potentially producing falsely low results that mimic central adrenal insufficiency. Pre-chilled EDTA tubes, immediate icing, and centrifugation within 15 minutes are non-negotiable for reliable results.
Can lifestyle factors cause abnormal ACTH?
Yes. Chronic psychological stress, sleep deprivation, overtraining, and inflammatory illness all chronically activate the HPA axis and raise ACTH. Prolonged HPA hyperactivation can eventually lead to receptor downregulation and relative cortisol resistance. Conversely, prolonged burnout states are associated with reduced CRH-ACTH drive and a flattened diurnal rhythm that produces low-normal ACTH and cortisol despite significant symptoms.
Content authored and clinically reviewed by Brian Lamkin, DO, founder of The Lamkin Clinic in Edmond, Oklahoma. Brian Lamkin, DO has 25+ years of experience in functional and regenerative medicine. This page reflects current functional medicine practice standards and is updated as new clinical evidence becomes available.
HPA axis dysregulation is measurable. ACTH and cortisol together reveal whether fatigue, weight gain, and poor stress resilience have a hormonal explanation.
Schedule a consultation for comprehensive HPA axis evaluation including ACTH, cortisol, and DHEA-S.
Schedule a ConsultationMedical Disclaimer: This content is provided for educational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Lab interpretation should always be performed in clinical context by a qualified healthcare provider. Reference ranges and optimal targets may vary based on individual patient history, clinical presentation, and laboratory methodology. Schedule a consultation to discuss your specific results with Dr. Lamkin.