The adrenal glands produce more than a half-dozen distinct hormones across two structurally different regions: an outer cortex that makes steroid hormones and an inner medulla that releases catecholamines. The best-known outputs are cortisol, aldosterone, DHEA, epinephrine, and norepinephrine, but the full list includes several lesser-known molecules with their own physiological roles. Because each hormone serves a different purpose and is regulated by a different signaling system, the adrenal glands act less like a single organ and more like two glands fused together during evolution.
Aldosterone and Fluid Balance
The outermost layer of the adrenal cortex, called the zona glomerulosa, produces aldosterone. Aldosterone’s primary job is to keep your blood pressure and electrolyte levels stable. It does this by telling the kidneys to hold onto sodium and water while releasing potassium. When blood pressure drops or potassium levels rise, a cascade known as the renin-angiotensin system ramps up aldosterone secretion. Angiotensin II and potassium are the two most important signals driving that release.1PubMed. Aldosterone biosynthesis, regulation, and classical mechanism of action Additional local signals within the adrenal gland itself can also fine-tune how much aldosterone the zona glomerulosa puts out.2PubMed. Paracrine Regulation of Aldosterone Secretion in Physiological and Pathophysiological Conditions
What makes aldosterone unusual compared to cortisol or DHEA is that it operates largely independent of signals from the brain. While cortisol production depends heavily on a brain-to-adrenal communication chain, aldosterone is governed more directly by the kidneys and by circulating potassium. That independence matters clinically: diseases that damage the brain’s pituitary gland can shut down cortisol production while leaving aldosterone relatively intact.
Cortisol and the Stress Response
Cortisol is produced in the middle layer of the cortex, the zona fasciculata, and is probably the most talked-about adrenal hormone. It is often called “the stress hormone,” though that label undersells what it does. Beyond helping you cope with immediate threats, cortisol regulates blood sugar, influences how your body stores fat, modulates inflammation, and helps maintain blood pressure. It also shapes immune function: cortisol reduces the activity and proliferation of certain white blood cells, suppresses the production of inflammatory signaling molecules, and dials down the killing ability of natural killer cells.3PubMed Central. Regulation of Stress-Induced Immunosuppression in the Context of Neuroendocrine, Cytokine, and Cellular Processes This is why prolonged stress or medical use of cortisol-like drugs can leave people more vulnerable to infections.
Cortisol secretion follows a pronounced daily rhythm. Levels typically peak in the early morning and trough around midnight. This pattern is orchestrated by a communication chain running from the hypothalamus to the pituitary gland to the adrenal cortex, and that chain is itself synchronized to the body’s internal clock system. Disruption of either the stress-signaling pathway or the circadian clock can throw cortisol rhythms off, contributing to metabolic problems, mood disorders, and immune dysfunction.4PubMed Central. Circadian endocrine rhythms: the hypothalamic-pituitary-adrenal axis and its actions Researchers have also found that local regulatory mechanisms within the adrenal gland itself help shape this rhythm, meaning the daily cortisol cycle is not simply a top-down command from the brain.5PubMed. Circadian rhythm of adrenal glucocorticoid: its regulation and clinical implications
Cortisol’s close relative corticosterone is also secreted by the adrenal cortex. In humans, cortisol is the dominant glucocorticoid, but corticosterone is the primary one in rodents, which is worth knowing because much of the research you see on “stress hormones” in animal models is actually studying corticosterone, not cortisol. Both hormones bind to the same pair of receptors in the brain and body, though with different affinities.6PubMed Central. Coping with the multifaceted and multifunctional role of cortisol in the brain
DHEA and Other Adrenal Androgens
The innermost cortical layer, the zona reticularis, produces weak androgens, the most abundant being dehydroepiandrosterone (DHEA) and its sulfate form DHEA-S. These are the most plentiful steroid hormones circulating in humans, yet they are not potent hormones themselves. Instead, they act as raw material that other tissues convert into testosterone, estradiol, and other active sex steroids as needed.7PubMed Central. The Sex Hormone Precursors Dehydroepiandrosterone (DHEA) and Its Sulfate Ester Form (DHEAS): Molecular Mechanisms and Actions on Human Body This local conversion happens inside individual cells of target tissues: skin, bone, fat, the brain, and reproductive organs all have the enzymatic machinery to turn DHEA into more potent hormones and then inactivate them before they leave the cell.8Frontiers in Neuroendocrinology. DHEA and Its Transformation into Androgens and Estrogens in Peripheral Target Tissues: Intracrinology
Which active hormones DHEA gets turned into depends on where it ends up. Animal research shows that DHEA is preferentially converted into androgens within the adrenal gland itself, whereas its conversion to estrogens happens mainly in the ovary.9PLoS ONE. Ample Evidence: Dehydroepiandrosterone (DHEA) Conversion into Activated Steroid Hormones Occurs in Adrenal and Ovary in Female Rat This tissue-specific routing means a single precursor hormone can support very different downstream effects depending on the organ processing it.
Beyond serving as a precursor, DHEA and DHEA-S appear to have direct biological effects of their own, including neuroprotective, anti-inflammatory, and immune-modulating actions.7PubMed Central. The Sex Hormone Precursors Dehydroepiandrosterone (DHEA) and Its Sulfate Ester Form (DHEAS): Molecular Mechanisms and Actions on Human Body These direct effects are an active area of research and help explain why falling DHEA levels in older adults seem to track with multiple aspects of aging, a topic covered further below.
Epinephrine and Norepinephrine From the Medulla
The adrenal medulla is the inner core of the gland and has a completely different origin and function from the cortex. Its specialized chromaffin cells produce and secrete three catecholamines: dopamine, norepinephrine, and epinephrine.10PubMed Central. Intricacies of the Molecular Machinery of Catecholamine Biosynthesis and Secretion by Chromaffin Cells of the Normal Adrenal Medulla and in Pheochromocytoma and Paraganglioma Of these, epinephrine (adrenaline) is the medulla’s signature product, while norepinephrine (noradrenaline) is also released in substantial amounts. Dopamine is produced in smaller quantities.
During a fight-or-flight response, the surge of epinephrine and norepinephrine from the medulla raises blood pressure and cardiac output, relaxes bronchial smooth muscle so you can breathe more easily, widens your pupils, and triggers metabolic changes that flood the bloodstream with glucose and free fatty acids for quick energy.11Comprehensive Physiology. Peripheral and Central Effects of Circulating Catecholamines These effects are mediated by a family of adrenergic receptors spread across nearly every organ system. Norepinephrine predominantly activates alpha receptors and beta-1 receptors in the heart, while epinephrine hits all alpha and beta receptor subtypes, giving it a broader range of effects on blood vessels, the lungs, the uterus, and fat tissue.12PubMed. Adrenergic receptors and cardiovascular effects of catecholamines
Epinephrine’s metabolic effects extend beyond short-term emergencies. Acutely, it raises blood sugar and induces insulin resistance.13PubMed. Epinephrine and the metabolic syndrome This matters clinically because chronically elevated catecholamine levels, as seen in certain tumors, can contribute to sustained hypertension and metabolic disturbances.
How the Cortex Supports the Medulla
Although the cortex and medulla are often described as if they were independent organs that happen to share an address, they actually depend on each other. The most striking example is the production of epinephrine itself. Chromaffin cells need the enzyme PNMT to convert norepinephrine into epinephrine, and the expression of that enzyme is controlled in part by cortisol flowing inward from the surrounding cortex.14PubMed Central. Epinephrine biosynthesis: hormonal and neural control during stress When cortisol levels fall, as in experimental removal of the pituitary gland, PNMT production drops and epinephrine output declines. Restoring glucocorticoid levels brings the enzyme and epinephrine production back to normal.15PubMed. The role of compartmentalization of epinephrine in the regulation of phenylethanolamine N-methyltransferase synthesis in rat adrenal medulla
This relationship is made possible by the gland’s unusual blood supply. Arteries entering the adrenal gland branch into capillaries that drain from the cortex inward through the medulla, bathing the chromaffin cells in cortisol-rich blood before the blood exits the gland through its central vein. It is an elegant arrangement: the medulla sits downstream of the cortex’s own output, ensuring that stress-driven cortisol spikes can amplify epinephrine production almost immediately.
A Hormone Most People Miss: Deoxycorticosterone
Deoxycorticosterone (DOC) is a steroid intermediate that the adrenal cortex produces on the way to making aldosterone and cortisol. It has weak mineralocorticoid activity on its own, meaning it can influence sodium and water retention to a modest degree. But DOC has a second life that attracts more research interest: the body can convert it into a neuroactive steroid called allotetrahydrodeoxycorticosterone (THDOC), which acts as a powerful positive modulator of GABA receptors in the brain. This gives THDOC anxiolytic and anticonvulsant properties.16PubMed. Physiological role of adrenal deoxycorticosterone-derived neuroactive steroids in stress-sensitive conditions In other words, a byproduct of adrenal steroid production doubles as a natural anxiety-reducing compound. The clinical implications are still being explored, but this pathway may help explain why some stress-related conditions involve changes in anxiety thresholds.
How Adrenal Output Changes Over a Lifetime
Adrenal hormone production is not static. The most dramatic shift involves DHEA and DHEA-S. During childhood, a process called adrenarche triggers the zona reticularis to begin pumping out these androgens, contributing to the development of body odor, oily skin, and early pubic hair. DHEA levels climb through the teens, peak around the third decade of life, and then begin a long, steady decline.17PubMed Central. Adrenal Androgens and Aging By old age, circulating DHEA can fall to as little as a tenth or a fifth of peak values, a gradual slide sometimes called “adrenopause.”18PubMed Central. A review of age-related dehydroepiandrosterone decline and its association with well-known geriatric syndromes: is treatment beneficial?
In women, this decline may accelerate in the early forties. One study found a meaningful drop in DHEA-S starting in the 41-to-45 age group, with more than a third of women over 40 falling below a defined threshold.19PubMed Central. From adrenarche to aging of adrenal zona reticularis: precocious female adrenopause onset Because DHEA is a precursor to sex steroids made in peripheral tissues, falling levels mean less local androgen and estrogen production, which may contribute to changes in bone density, body composition, skin quality, and other age-related shifts. Whether supplementing DHEA in older adults meaningfully reverses any of these changes remains an open question.
Cortisol and aldosterone, by contrast, remain relatively stable with age in healthy people. The machinery that produces them does not undergo the same predictable decline, though diseases, medications, and chronic stress can alter their output at any age.
The Fetal Adrenal Gland Has Its Own Agenda
Before birth, the adrenal glands are proportionally enormous, sometimes rivaling the kidneys in size. The fetal adrenal has a large inner zone (the fetal zone) that churns out massive quantities of DHEA-S. But this DHEA-S is not for the fetus itself. It is shipped to the placenta, which lacks the enzymes to make estrogens from scratch. The placenta converts DHEA-S into estradiol and estriol, hormones critical for maintaining the pregnancy and preparing the mother’s body for delivery.20PubMed Central. Development and function of the fetal adrenal Estriol, in particular, is the hallmark estrogen of pregnancy and is used as a clinical marker. After birth, the fetal zone rapidly shrinks and disappears, and the adrenal glands reorganize into the three-layer cortex seen in adults.
When the Adrenal Glands Produce Too Much
Overproduction of any adrenal hormone leads to a recognizable clinical syndrome. Excess cortisol causes Cushing syndrome, associated with central weight gain, high blood sugar, muscle weakness, thinning skin, hypertension, mood changes, and immune suppression.21JAMA. Cushing Syndrome: A Review Even milder degrees of cortisol excess that do not produce the classic round-faced, purple-stretch-mark appearance can quietly increase cardiovascular and bone-fracture risk.22PubMed Central. Hypercortisolism: Causes, Consequences and Clinical Significance – A Review of Pathophysiology
Excess aldosterone, a condition called primary aldosteronism, disrupts the normal feedback between sodium and aldosterone, leading to inappropriate salt retention, high blood pressure, and cardiovascular damage.23PubMed. Primary aldosteronism and salt It is now recognized as one of the more common causes of treatment-resistant hypertension, and screening for it has become routine in patients whose blood pressure does not respond well to standard medications.
On the medulla side, a tumor called a pheochromocytoma can secrete enormous amounts of catecholamines. Roughly 80 to 85 percent of these tumors arise in the adrenal medulla itself.24PubMed. Pheochromocytomas and Hypertension The hallmark symptoms are episodes of severe hypertension, sweating, headaches, and pounding heartbeat. High circulating catecholamines can damage the cardiovascular system and, in rare cases, be fatal if untreated.25PubMed Central. Hypertension in pheochromocytoma: characteristics and treatment
When the Adrenal Glands Produce Too Little
Primary adrenal insufficiency, historically known as Addison disease, involves a deficiency of all cortical hormones at once. The most common cause in developed countries is autoimmune destruction of the adrenal cortex, though infections like tuberculosis, certain medications, inherited enzyme defects, and surgical removal can also be responsible.26JAMA. Adrenal Insufficiency in Adults: A Review Without adequate glucocorticoid replacement, patients are vulnerable to adrenal crisis, a potentially life-threatening emergency marked by dangerously low blood pressure, confusion, and sodium imbalance.
A subtler and far more common form of adrenal suppression comes from taking glucocorticoid medications. Prednisone, dexamethasone, and even inhaled or topical steroids can signal the brain to stop sending stimulation to the adrenal cortex, causing it to shrink and lose the ability to produce cortisol on its own. This can happen not only with high-dose, long-term use but also with short courses or low doses.27PubMed Central. Glucocorticoid Withdrawal-An Overview on When and How to Diagnose Adrenal Insufficiency in Clinical Practice The practical consequence is that abruptly stopping a steroid medication can leave you without enough cortisol, so tapering under medical guidance is standard practice.
Congenital adrenal hyperplasia (CAH) represents a different kind of underproduction problem. In CAH, an inherited enzyme deficiency, most commonly of 21-hydroxylase, blocks cortisol synthesis. The brain senses low cortisol levels and floods the adrenal glands with stimulating signals, which enlarges them but cannot fix the enzyme defect. Instead, precursor molecules pile up and spill over into androgen production, causing excess masculinization in affected girls and early puberty in boys.28European Journal of Endocrinology. Congenital adrenal hyperplasia: molecular mechanisms resulting in 21-hydroxylase deficiency CAH is a vivid illustration of how a blockage in one adrenal pathway can redirect steroid production into another.
Salivary Cortisol and Modern Diagnostic Testing
Because cortisol follows such a strong daily rhythm, the timing of a blood draw matters enormously when doctors suspect a cortisol problem. A morning blood test showing high cortisol might be completely normal, while the same level at midnight would be a red flag. This is one reason salivary cortisol testing has gained traction. Saliva can be collected at home at specific times of day, giving clinicians a window into the cortisol rhythm without the stress of a hospital visit. Late-night salivary cortisol measurements show strong sensitivity for detecting Cushing syndrome, and combining them with an overnight dexamethasone suppression test, where you take a small cortisol-suppressing pill at bedtime and check levels the next morning, can reliably separate true cortisol excess from the mildly elevated cortisol sometimes seen in obesity or chronic stress.29The Journal of Clinical Endocrinology & Metabolism. Out-Patient Screening for Cushing’s Syndrome: The Sensitivity of the Combination of Circadian Rhythm and Overnight Dexamethasone Suppression Salivary Cortisol Tests
More recently, salivary cortisone (a related metabolite) has been evaluated as an alternative marker. In one clinical study, morning salivary cortisone after overnight dexamethasone suppression picked up every case of cortisol excess, with an agreement rate above 94 percent compared to serum cortisol.30PubMed Central. Adrenal Morning Salivary Cortisone Versus Serum Cortisol in the Overnight Dexamethasone Suppression Test (ODNST): Evaluation in a Clinical Setting For patients with adrenal incidentalomas, tumors found incidentally on imaging done for other reasons, dexamethasone-suppressed cortisol testing, whether in blood or saliva, tends to be more specific than a single late-night sample.31European Journal of Endocrinology. Late-night and low-dose dexamethasone-suppressed cortisol in saliva and serum for the diagnosis of cortisol-secreting adrenal adenomas These developments are slowly making outpatient screening for cortisol disorders more accessible and less reliant on the inconvenience and expense of overnight hospital stays.
An Evolutionary Quirk Worth Knowing
The two-part structure of the adrenal gland, steroid-producing cortex on the outside and catecholamine-producing medulla on the inside, is a distinctly mammalian arrangement. In fish, the equivalent cell types exist as separate, scattered clusters in different parts of the body. Through reptiles and eventually mammals, these clusters gradually merged into a single compact organ, with the steroid-producing tissue wrapping around the catecholamine-producing tissue.32PubMed Central. The Adrenal Gland of Squamata (Reptilia): A Comparative Overview The payoff of that merger is the cortex-to-medulla blood flow described earlier: by encasing the medulla, the cortex can deliver cortisol directly to chromaffin cells, supporting efficient epinephrine production. The anatomy of the adrenal gland, in other words, is not an accident. It reflects hundreds of millions of years of selection pressure favoring a tighter partnership between steroid and catecholamine signaling during stress.