What Causes Overactive Adrenal Glands?

Overactive adrenal glands result from a surprisingly long list of causes, ranging from tumors growing inside the glands themselves to signals sent by tumors elsewhere in the body, inherited enzyme defects, and even receptors on adrenal cells that respond to hormones they were never supposed to respond to. The adrenal glands sit atop each kidney and produce several families of hormones, including cortisol, aldosterone, androgens, and adrenaline-like chemicals called catecholamines. When any part of this machinery runs too hot, the consequences ripple across blood pressure, metabolism, bone health, and mood. Because the glands have distinct zones that make different hormones, the specific cause determines which hormone floods the body and what symptoms follow.

Tumors Inside the Adrenal Glands

The most straightforward cause of adrenal overactivity is a growth within the gland itself that churns out hormone without waiting for the brain’s usual “go” signal. In most cases, this growth is a benign adenoma, a small nodule of adrenal tissue that has acquired mutations allowing it to produce cortisol on its own. Less commonly, the culprit is an adrenal cancer. Both adults and children can develop these lesions, and the spectrum also includes several forms of bilateral hyperplasia, where both adrenal glands enlarge and overproduce hormone at the same time.¹ When cortisol overproduction stems from one of these adrenal lesions, ACTH levels in the blood drop, because the brain recognizes there is already too much cortisol and stops asking for more. That low ACTH reading is what separates an adrenal cause from the pituitary-driven causes discussed below.²

At the molecular level, the majority of benign cortisol-producing adenomas carry defects in a signaling pathway called cAMP, which normally helps fine-tune how much hormone an adrenal cell releases. Adrenal cancers, by contrast, tend to involve mutations in tumor-suppressor genes like TP53 and abnormal growth-factor signaling.¹ This distinction matters clinically because it influences how aggressively doctors pursue treatment and how closely they monitor the patient afterward.

When the Problem Starts in the Brain

The adrenal glands do not operate independently. They take orders from ACTH, a hormone released by the pituitary gland at the base of the brain. If a small tumor forms in the pituitary and pumps out too much ACTH, the adrenals dutifully respond by overproducing cortisol. This particular scenario is called Cushing’s disease and is the most common form of ACTH-dependent cortisol excess.³ Pituitary MRI can often spot the tumor, although it is sometimes so small that additional sampling of blood from veins near the pituitary is needed to confirm the diagnosis.³

In rarer cases, a tumor somewhere else in the body produces ACTH or a related hormone and drives the adrenals into overdrive. Tumors in the lungs, thymus, thyroid, and pancreas are the usual offenders, including small cell lung carcinoma, bronchial carcinoid tumors, and certain neuroendocrine tumors in the abdomen.³ Finding the source can be a challenge, and clinicians use a combination of CT, MRI, and nuclear medicine scans to track it down. The key diagnostic clue in both pituitary and ectopic cases is that ACTH levels are elevated, the opposite of what happens when the adrenal glands themselves harbor a tumor.

Aldosterone Overproduction

Cortisol gets most of the attention, but the adrenal cortex also makes aldosterone, the hormone that regulates sodium, potassium, and blood pressure. When aldosterone production goes unchecked, the result is primary hyperaldosteronism, sometimes still called Conn’s syndrome. It is one of the most common treatable causes of high blood pressure, and many people with resistant hypertension turn out to have it.

Two main patterns account for most cases. In roughly half of patients, a single aldosterone-producing adenoma in one adrenal gland is to blame. In the other half, both adrenal glands are diffusely enlarged, a condition known as bilateral adrenal hyperplasia.⁴ Imaging studies show that the adrenal glands in patients with bilateral hyperplasia are measurably larger than those of patients with a single adenoma or healthy controls.⁵ On the genetic side, mutations in the KCNJ5 gene are the most frequent genetic alteration found in primary aldosteronism.⁶ The distinction between one-sided and two-sided disease is critical because a solitary adenoma can be surgically removed, often curing the high blood pressure, whereas bilateral hyperplasia usually requires lifelong medication.

Catecholamine Overproduction From the Adrenal Medulla

The inner core of each adrenal gland, the medulla, makes adrenaline and noradrenaline. A tumor of the medulla called a pheochromocytoma releases these catecholamines in bursts or continuously, producing dramatic spikes in blood pressure, a pounding heart, sweating, and headaches. Beyond those classic symptoms, chronic catecholamine flooding pushes the body into a hypermetabolic state. One study found that resting energy expenditure in patients with a pheochromocytoma was about 10% higher than predicted, and that it dropped back to normal after the tumor was removed.⁷ Markers of inflammation also fell after surgery, suggesting the excess catecholamines had been driving a low-grade inflammatory response.⁷

Pheochromocytomas have one of the highest rates of hereditary involvement among endocrine tumors. Three well-known genetic syndromes explain a substantial share of cases: von Hippel-Lindau disease, multiple endocrine neoplasia type 2, and neurofibromatosis type 1.⁸ On top of those, several genes encoding parts of the succinate dehydrogenase enzyme complex, including SDHB, SDHC, and SDHD, also predispose carriers to these tumors and their close relatives, paragangliomas.⁹ In recent years, additional susceptibility genes have been identified, widening the list of people who should consider genetic testing after a diagnosis.⁸

Congenital Adrenal Hyperplasia

Not all adrenal overactivity involves a tumor. Congenital adrenal hyperplasia is an inherited group of enzyme defects that disrupt the normal assembly line converting cholesterol into cortisol. When one enzyme in the chain is missing or sluggish, the glands compensate by growing larger and diverting precursor molecules into other hormones, often androgens. The result is excess androgens despite low or borderline cortisol. Over 95% of cases trace to a deficiency of the enzyme 21-hydroxylase, encoded by the CYP21A2 gene, and researchers have catalogued more than 230 disease-causing variants of that gene.¹⁰

The condition exists on a spectrum. In its severe, “classic” form, it can cause a life-threatening salt-wasting crisis in newborns and ambiguous genitalia in girls. The milder, “nonclassic” form may not surface until adolescence or adulthood, showing up as acne, irregular periods, or excess body hair. Because the adrenals are being whipped into overdrive by the brain trying to get cortisol levels up, treatment typically involves replacing cortisol from outside to quiet the signal loop. This is one scenario where the adrenals are simultaneously overproducing one hormone (androgens) and underproducing another (cortisol).

Adrenal Incidentalomas and Mild Autonomous Cortisol Secretion

Modern imaging has introduced an unexpected wrinkle. When someone gets a CT scan for an unrelated reason, a small adrenal mass turns up about 5% of the time.¹¹ Most of these so-called incidentalomas are benign adenomas and most are harmless. But somewhere between 20% and 50% of patients with an adrenal adenoma test positive for mild autonomous cortisol secretion, or MACS, meaning the nodule is quietly trickling out cortisol without permission from the pituitary.¹²

MACS does not look like full-blown Cushing’s syndrome. Patients rarely develop a moon face or purple stretch marks. Instead, the slow, low-grade cortisol excess is linked to a higher likelihood of metabolic problems like diabetes, high blood pressure, weak bones, and vertebral fractures, and it has even been associated with increased mortality.¹³ This makes MACS one of the most common but least recognized forms of adrenal overactivity. Whether surgery or watchful waiting is the right response remains an active debate in endocrinology, and decisions often hinge on the individual patient’s age, other health conditions, and degree of cortisol excess.

Aberrant Receptors and Unusual Triggers

Some of the most fascinating causes of adrenal overactivity involve receptors that should not be there. Adrenal cells normally respond to ACTH and a small number of other signals. But in certain forms of bilateral adrenal hyperplasia, the cells sprout receptors for hormones that have no business talking to the adrenal cortex, such as gastric inhibitory polypeptide (a gut hormone released after eating), vasopressin, serotonin, and luteinizing hormone. In a study of patients with bilateral macronodular adrenal hyperplasia, every single patient had one or two of these aberrant receptors.¹⁴ One study confirmed that vasopressin was able to stimulate cortisol secretion through receptor types (V1b and V2) not normally found in adrenal tissue.¹⁵

This explains some otherwise puzzling clinical scenarios. A patient whose cortisol spikes after every meal may have adrenal cells responding to a gut hormone. A patient whose cortisol rises with every surge of luteinizing hormone may have a predictable hormonal pattern tied to the menstrual cycle. And then there is pregnancy. Rising levels of human chorionic gonadotropin (hCG) during pregnancy can stimulate aberrantly expressed LH/hCG receptors on adrenal cells, leading to transient Cushing’s syndrome that appears during pregnancy and resolves afterward.¹⁶ Research suggests these receptor-positive cells persist between pregnancies but lie dormant until the next exposure to hCG.¹⁷ These cases are rare, but they illustrate how creatively adrenal tissue can be hijacked.

Pseudo-Cushing States

High cortisol does not always mean something is structurally wrong with the adrenals or the pituitary. Conditions like severe depression, eating disorders, and chronic heavy alcohol use can ramp up cortisol output through changes in the brain’s stress-hormone axis. This collection of look-alikes is sometimes called pseudo-Cushing syndrome. The mechanisms vary: in neuropsychiatric disorders, an exaggerated post-awakening surge in cortisol and reduced activity of enzymes that deactivate cortisol have been reported; in eating disorders, elevated levels of the brain’s cortisol-triggering hormone (CRH), changes in how cortisol binds to its carrier protein, and slower cortisol clearance may all contribute.¹⁸

Distinguishing pseudo-Cushing from true Cushing’s is important because the treatment paths are completely different. A patient whose cortisol normalizes after getting depression treated or stopping alcohol does not need adrenal surgery. The CRH stimulation test, which works by probing whether cortisol responds in the pattern expected of pituitary-driven disease, has a sensitivity around 91% and a specificity around 95% for identifying pituitary Cushing’s specifically.¹⁹ Endocrinologists typically combine this with other tests and clinical judgment, since no single test is perfect.

Sleep, Stress, and the Cortisol Rhythm

Even without a tumor, aberrant receptor, or enzyme defect, lifestyle factors can push cortisol higher than normal. One study found that a single night of total sleep deprivation significantly increased cortisol levels compared to baseline. Interestingly, when participants experienced chronic circadian misalignment over several weeks, their average cortisol levels actually dropped, suggesting the body’s stress response can be disrupted in both directions depending on the type of sleep disturbance.²⁰ This kind of disruption is not the same as a disease state with structurally overactive glands, but for shift workers, long-haul travelers, and people with chronic insomnia, the practical effect on cortisol rhythms is real and measurable.

The gut microbiome adds another layer. Research shows that gut bacteria can modulate the brain-adrenal stress axis throughout life, and appropriate cortisol concentrations are essential for normal brain development, learning, and memory.²¹ Much of this work is still in early stages and drawn from animal models, so it would be premature to say that taking a probiotic can meaningfully change adrenal output in people. But it opens a window into how the signals reaching the adrenal glands are shaped by parts of the body far removed from the endocrine system.

Environmental Chemicals and the Adrenal Cortex

Endocrine-disrupting chemicals, substances found in plastics, pesticides, and industrial compounds, have drawn increasing scrutiny for their potential to interfere with adrenal function. Laboratory studies suggest these chemicals can alter gene activity, cell signaling, and steroid production in adrenal tissue.²² Whether these in-vitro effects translate into clinically meaningful adrenal overactivity in living humans remains an open question. The evidence is strongest for disrupted steroid profiles rather than frank overproduction of any single hormone, and most regulatory agencies treat this as a research priority rather than a settled concern. Still, for anyone wondering whether everyday chemical exposures could nudge adrenal activity, the short answer is that they probably can, but the magnitude and clinical significance are not yet clear.

Medications That Affect Adrenal Activity

Ironically, one of the most common ways adrenal function goes off the rails involves the opposite of overactivity. Long-term use of glucocorticoid medications like prednisone suppresses the brain’s signal to the adrenals via negative feedback, eventually leaving the glands underpowered. Recovery after stopping the medication can take six months to a year.²³ This is relevant here because people sometimes conflate a post-steroid rebound in symptoms with adrenal overactivity, when what is actually happening is a withdrawal state.

On the treatment side, when overactive adrenals need to be reined in urgently, medications that block steroid-producing enzymes in the gland are used. Ketoconazole, originally an antifungal drug, was shown to significantly blunt the adrenal cortisol response to ACTH stimulation for up to eight hours after a single dose.²⁴ Etomidate, an anesthetic agent, blocks two key enzymes in the cortisol production chain and is sometimes used in critical-care settings when cortisol levels need to come down fast.²⁵ Newer drugs targeting specific steroid-synthesis steps have entered clinical use more recently, but ketoconazole and etomidate illustrate how well the biochemistry of cortisol production can be targeted when a patient is in danger from excess hormone.

Why the Specific Cause Matters So Much

One thing that catches many patients off guard is how differently two people with “overactive adrenal glands” can present. Someone with a cortisol-producing adenoma may gain weight, bruise easily, and develop high blood sugar. Someone with an aldosterone-producing adenoma may look perfectly healthy except for stubborn high blood pressure and low potassium. Someone with a pheochromocytoma may be thin, anxious, and plagued by episodes of flushing and rapid heartbeat. And someone with congenital adrenal hyperplasia may have normal or even low cortisol but excess androgens causing acne and irregular cycles. The umbrella term “overactive adrenal glands” disguises the fact that these are fundamentally different diseases with different causes, different hormones, and different treatments.

Getting to the right diagnosis usually involves blood and urine tests for specific hormones, followed by imaging if those tests point to a structural problem. The initial workup typically separates cortisol-driven from aldosterone-driven from catecholamine-driven overactivity, then narrows down whether the signal is coming from the adrenal glands themselves or from somewhere else. Because some of the most common forms, like MACS, fly under the radar for years, anyone with unexplained metabolic problems and an adrenal nodule found on imaging should have at least a screening conversation with an endocrinologist about whether the nodule is doing more than just sitting there.