Adrenal Health, Cortisol & “Adrenal Fatigue”

Written by Empire Medical Training Editorial Team

Medically reviewed by Betsy Greenleaf, DO Board-Certified OB/GYN & Urogynecologist; Empire Director of Anti-Aging

Updated June 2026 ·11 min read

Few topics in anti-aging medicine generate more patient questions — and more confusion — than the adrenal glands and cortisol. Patients arrive convinced they have “adrenal fatigue,” a term that fills wellness blogs but does not appear in any endocrinology textbook. The honest clinical position is that the popular label is not a real diagnosis, yet the physiology underneath the conversation is very real: cortisol is a powerful hormone with a daily rhythm, that rhythm genuinely gets disrupted under chronic stress, and that disruption ripples through the rest of the endocrine system.

This guide, part of Empire's hormone replacement therapy resource center, gives providers an evidence-honest overview of cortisol and the HPA axis, drawing on the clinical reasoning Dr. Betsy Greenleaf, DO teaches in Empire's hormone curriculum. It is clinical education, not medical advice, and it does not reproduce any course protocols.

The HPA axis and cortisol

Cortisol does not act alone. It is the output of a tightly regulated feedback loop called the HPA axis — the hypothalamic-pituitary-adrenal axis. The hypothalamus signals the pituitary, the pituitary signals the adrenal glands sitting atop the kidneys, and the adrenals release cortisol. Cortisol then feeds back to the brain to dial the signal down, the same way a thermostat shuts off the furnace once the room warms. This is the body's central stress-response system.

When the brain perceives a threat, the sympathetic nervous system activates — the classic fight-or-flight state. As Greenleaf frames it in the course, when the sympathetic system is switched on, energy is pulled away from digestion and reproduction and redirected toward survival. Stress triggers the production of steroids such as cortisol, which the body needs in short bursts to survive. A surge of cortisol in a genuine emergency is healthy and adaptive. The problem is not the surge; it is the surge that never switches off.

Just as important as how much cortisol the body makes is when it makes it. Healthy cortisol follows a diurnal (circadian) rhythm: it rises in the early morning to get you out of bed, peaks shortly after waking, and tapers down across the day so it is low at night to allow sleep. A normal curve climbs in the morning and comes down by noon and evening. When that curve flattens, inverts, or stays elevated into the evening, the rhythm — not the gland — is what has gone wrong.

What cortisol actually does

Cortisol has a reputation as the “bad” stress hormone, but it is essential to life. Its jobs cut across nearly every system in the body:

• Blood sugar and metabolism. Cortisol raises blood glucose by promoting the breakdown of stored fuel, ensuring the brain and muscles have energy available during stress. Chronically elevated cortisol, however, drives the metabolic picture that favors central weight gain and insulin resistance.
• Immune modulation. Cortisol is a natural anti-inflammatory — the reason synthetic glucocorticoids are prescribed to calm inflammation. In short bursts it is protective; sustained high levels can suppress immune function.
• Blood pressure and circulation. Cortisol helps maintain vascular tone and blood pressure, part of keeping the body primed to respond.
• Sleep and the daily clock. The morning cortisol peak is part of the wake signal; an evening cortisol that stays high is a common reason patients describe being “tired but wired” and unable to wind down.

Greenleaf emphasizes the bidirectional link between cortisol and sleep specifically. When sleep gets disrupted, it affects cortisol, and disordered cortisol disrupts sleep further — a chicken-or-egg loop that has to be broken from both sides. She also notes a behavioral trap clinicians should screen for: patients who exercise late at night may be spiking cortisol at exactly the wrong time and sabotaging the sleep they need.

The “adrenal fatigue” debate

Here is where evidence and marketing part ways. “Adrenal fatigue” is a popular term, not a validated medical diagnosis. The Endocrine Society and other major bodies have explicitly stated that the concept — that prolonged stress “exhausts” the adrenal glands until they can no longer produce adequate cortisol — is not supported by scientific evidence. Symptoms commonly attributed to it (fatigue, brain fog, low energy, poor stress tolerance) are real, but they are non-specific and overlap with many genuine conditions, from hypothyroidism to anemia to depression to sleep disorders.

What does exist are well-defined adrenal disorders, and they must not be missed:

• Addison's disease (primary adrenal insufficiency) — the adrenals genuinely fail to make enough cortisol (and often aldosterone). It is diagnosable, potentially life-threatening, and requires hormone replacement under endocrinology care.
• Cushing's syndrome — the opposite problem, a sustained excess of cortisol from a tumor or exogenous steroids, with its own distinct signs and formal workup.

So the responsible framing is this: dismiss the label, not the patient. Greenleaf's teaching reflects the more accurate model — under chronic stress, “it's not that they're not making cortisol anymore.” Instead, the cortisol rhythm becomes dysregulated: the curve flattens, the morning rise blunts, or evening levels climb. That is a measurable, addressable phenomenon. It is simply a different thing from glands that have “burned out,” and providers serve patients best by naming it accurately rather than selling a diagnosis that does not exist.

Cortisol and the other hormones

The reason cortisol matters so much in anti-aging practice is that it does not stay in its own lane — it pulls on the entire steroid pathway. Greenleaf builds her hormone teaching around a single map: cholesterol is the parent hormone, converting into pregnenolone, then branching toward progesterone, DHEA, testosterone, and estrogen, or down the cortisol branch.

The pathway is not a one-way street. As she puts it, in a relaxed, parasympathetic state, cholesterol flows down the pathway into pregnenolone and progesterone and on into testosterone and estrogen. But the moment the sympathetic system fires under stress, priorities shift. The body diverts raw material toward cortisol — clinically, the precursors are “stolen” to make cortisol, leaving less to build sex hormones. This is why she says she goes “immediately first to look at cortisol” in a workup: a stressed cortisol picture explains a great deal downstream.

• DHEA. DHEA, an adrenal androgen and precursor, frequently runs low in patients with a disrupted cortisol rhythm — the same stress that drives cortisol depletes DHEA. See our companion guide on DHEA therapy.
• Sex hormones. Chronic stress that prioritizes cortisol can suppress testosterone and estrogen production, which is why cortisol dysregulation and low sex-hormone levels so often appear together.
• Thyroid. Greenleaf notes a recurring pattern: high cortisol, low testosterone, and high estrogen can all contribute to low thyroid function. Cortisol and thyroid are deeply intertwined — see thyroid hormone optimization.
• Weight. Sustained cortisol elevation favors central fat storage and insulin resistance, knitting the stress response directly to metabolic and weight outcomes.

The practical lesson is that an isolated cortisol value tells you little. Cortisol is one reading on a connected dashboard, which is exactly why comprehensive hormone testing and lab panels assess it alongside DHEA, thyroid, and sex hormones rather than in isolation.

Testing cortisol

Because cortisol moves on a daily rhythm, the single most important testing principle is also the most overlooked: one cortisol value does not give you the full picture. A lone reading tells you the level at one moment but says nothing about the shape of the curve — and the shape is where the clinical information lives. Greenleaf repeatedly returns to this point with patient cases: knowing what time of day a sample was drawn is essential, and a single morning cortisol can look reassuring while the evening value is the real problem.

This is why rhythm-based testing matters. Rather than one draw, clinicians sampling across the day can map the curve — the morning rise, the midday descent, the evening trough — and see whether it is normal, flattened, or shifted. The goal is the pattern, not the point.

Why saliva comes up so often. In functional and anti-aging settings, salivary cortisol is frequently discussed because it measures the free (unbound), biologically active fraction and is convenient for collecting multiple time points at home. As Greenleaf teaches, saliva gives a better idea of what hormones are actually reaching the tissue, and is often described as a gold standard for steroid hormones — with the notable exception of testosterone, where serum remains standard. One critical caveat she stresses: serum, salivary, and urine results are not interchangeable and cannot be directly compared to one another. She also reminds providers that the patient should be in as relaxed a state as possible for testing — ideally holding off strenuous exercise for 24 to 48 hours beforehand — since a workout can transiently spike cortisol and skew the reading.

Whenever testing or symptoms raise concern for a true adrenal disorder — Addison's or Cushing's — that is a referral and a standard endocrine workup, not a rhythm-mapping exercise.

Management principles

Once a true adrenal disease has been ruled out, the management of a disrupted cortisol rhythm is, first and foremost, lifestyle-led. Greenleaf's case approach consistently begins not with a prescription but with the foundations: addressing diet, exercise, sleep, and stress reduction before anything else. The logic is straightforward — if chronic stress is driving the cortisol disruption, the most direct lever is the stress itself.

The principles she emphasizes, at a high level, include:

• Sleep is non-negotiable. She frames sleep as central, noting that people getting only five to six hours a night carry a substantially higher risk of obesity. Because patients rarely comply with “just sleep eight hours,” she favors realistic, incremental change — adjusting the sleep schedule by about fifteen minutes a day rather than demanding an overnight overhaul.
• Stress reduction. Shifting the nervous system out of chronic sympathetic activation and back toward a parasympathetic state is the core goal — this is what lets the steroid pathway flow toward sex hormones again instead of being diverted to cortisol.
• Exercise, timed wisely. Movement is beneficial, but Greenleaf cautions that exercise is itself a stressor; late-night workouts can spike cortisol and worsen sleep, and even one of her own patients cut back to alternating, shorter sessions for exactly this reason.
• Diet and nutrition. Stable blood sugar and adequate nutrition support a more stable cortisol pattern.

Greenleaf also mentions adaptogens such as ashwagandha as one tool that comes up in adrenal and thyroid support. The specific decision points — when an adaptogen or DHEA is appropriate, how it fits a given cortisol curve, dosing, and how it is sequenced with the rest of a hormone plan — are exactly the kind of individualized clinical judgment taught in Empire's hormone course, not something to reduce to a generic protocol on a public page. The headline for providers is the order of operations: rule out real disease, correct the lifestyle drivers first, then individualize.