Your adrenal glands are small, hormone-producing organs that sit on top of each kidney and influence everything from blood pressure and blood sugar to how your body responds to stress. Despite weighing only a few grams each, they release a range of hormones, including cortisol, aldosterone, adrenaline, and sex-hormone precursors, that keep you alive minute to minute. When something goes wrong with these glands, the effects can range from subtle fatigue to life-threatening crises, which makes understanding their normal function a good starting point for recognizing the disorders that follow.
Two Glands Packed Into One
Each adrenal gland is really two distinct tissues fused together. The outer layer, the cortex, makes steroid hormones from cholesterol. The inner core, the medulla, produces catecholamines like adrenaline and noradrenaline. These two parts have entirely different embryological origins: the cortex develops from the same tissue that forms the kidneys and reproductive organs, while the medulla comes from neural crest cells, the same lineage that gives rise to parts of the nervous system. In mammals, the two are bundled into a single organ, but in many pre-vertebrate species they exist as completely separate structures.
1IntechOpen. The Development and Anatomy of Adrenal GlandsThis arrangement is not just anatomical coincidence. The cortex has a local stimulatory effect on the medulla: cortisol produced in the outer layers flows inward through the gland’s blood supply and helps the medulla produce adrenaline efficiently. Without high local concentrations of cortisol reaching the medulla, adrenaline synthesis drops. The gland’s architecture, in other words, is part of how it works.
2PubMed. Local transfer of hormones between blood vessels within the adrenal gland may explain the functional interaction between the adrenal cortex and medullaWhat the Cortex Produces
The adrenal cortex is organized into three zones, each responsible for a different class of hormone. Together they handle blood sugar regulation, blood pressure control, and the production of sex-hormone building blocks.
Cortisol and Blood Sugar
Cortisol is the best-known product of the adrenal cortex and the main glucocorticoid in humans. One of its most important jobs is keeping blood sugar from dropping too low between meals. In the liver, cortisol blocks glucose usage and ramps up the production of new glucose from non-sugar sources, a process called gluconeogenesis. It does this by activating specific enzymes in the liver that push glucose back into the bloodstream.
3IntechOpen. Biological Effects of CortisolBeyond blood sugar, cortisol shapes immune function, affects bone density, influences mood, and helps the body respond to infection and injury. Cortisol levels are not static through the day. They peak in the early morning and fall in the evening, a rhythm driven by signaling from the brain’s hypothalamus and pituitary gland. When you are stressed, whether physically or psychologically, the brain overrides this daily rhythm and triggers a burst of cortisol to mobilize energy.
Aldosterone and Blood Pressure
Aldosterone is the principal mineralocorticoid, and its primary job is regulating sodium and potassium balance in the kidneys. When aldosterone levels rise, the kidneys hold onto more sodium and water while excreting more potassium. The net result is higher blood volume and, with it, higher blood pressure. Aldosterone’s role in managing potassium excretion in the kidney is one of the most well-established facts in kidney physiology.
4PubMed Central. Extrarenal Effects of Aldosterone on Potassium HomeostasisAldosterone release is controlled by a system called the renin-angiotensin-aldosterone system, or RAAS. When blood pressure drops or sodium falls, the kidneys release an enzyme called renin, which sets off a cascade that ultimately tells the adrenal cortex to pump out more aldosterone. RAAS is one of the body’s most important blood-pressure regulators. Recent research also shows that components of this system act locally within tissues, not just through the bloodstream, contributing to effects on the heart and blood vessels beyond simple pressure control.
5PubMed Central. A New Perspective on the Renin-Angiotensin SystemDHEA and Sex-Hormone Precursors
The innermost zone of the cortex produces androgens, most notably dehydroepiandrosterone (DHEA) and its sulfate form, DHEAS. These are not potent sex hormones on their own but serve as raw material that other tissues convert into testosterone and estrogen. DHEA and DHEAS are the most abundant steroid hormones circulating in the blood, and beyond serving as precursors to sex steroids, they appear to have neuroprotective, anti-inflammatory, and immune-modulating effects in their own right.
6PubMed Central. The Sex Hormone Precursors Dehydroepiandrosterone (DHEA) and Its Sulfate Ester Form (DHEAS): Molecular Mechanisms and Actions on Human BodyIn women, adrenal androgens are a meaningful source of circulating testosterone and estrogen, particularly after menopause when ovarian production declines. In men, the adrenal contribution to total testosterone is relatively minor compared to the testes. DHEA levels peak in early adulthood and decline steadily with age, which has fueled interest in DHEA supplements as an anti-aging strategy, though evidence that supplementation meaningfully reverses age-related changes remains limited.
The Medulla and the Fight-or-Flight Response
If the cortex handles longer-term metabolic housekeeping, the medulla handles emergencies. When your brain perceives a threat, nerve signals travel directly to the adrenal medulla, which responds in seconds by flooding the bloodstream with adrenaline (epinephrine) and noradrenaline (norepinephrine). These catecholamines accelerate your heart rate, widen your airways, redirect blood to muscles, and sharpen your senses. The synthesis of catecholamines depends on an enzyme called tyrosine hydroxylase, which acts as the rate-limiting step in the process.
7Wiley Online Library (Journal of Neuroendocrinology). Nicotinic stimulation of catecholamine synthesis and tyrosine hydroxylase phosphorylation in cervine adrenal medullary chromaffin cellsUnlike the cortex, which communicates through the bloodstream and hormonal cascades, the medulla is wired directly into the nervous system. The cells within it, called chromaffin cells, are essentially modified nerve cells. This direct neural wiring explains why adrenaline surges happen almost instantly. You feel the effects of the cortex over hours and days; you feel the medulla within a heartbeat.
How the Brain Keeps Cortisol in Check
Cortisol production is governed by a loop connecting the hypothalamus, the pituitary gland, and the adrenal cortex, commonly called the HPA axis. When the brain detects stress, the hypothalamus releases corticotropin-releasing hormone (CRH), which tells the pituitary to secrete adrenocorticotropic hormone (ACTH), which in turn instructs the adrenal cortex to release cortisol. Once cortisol reaches a certain level, it feeds back to both the hypothalamus and the pituitary to dial down CRH and ACTH, completing the loop.
8PubMed Central. Regulation of the Hypothalamic-Pituitary-Adrenocortical Stress ResponseThis negative feedback happens through several routes. Cortisol can act on structures in the brain like the hippocampus, which then sends inhibitory signals back to the hypothalamus. It can also act rapidly at the hypothalamus itself, binding to receptors on the surface of CRH-releasing neurons to shut them down within minutes. The system is calibrated to prevent runaway cortisol production, but it can be overwhelmed by chronic stress, illness, or tumors, which is where adrenal disorders enter the picture.
8PubMed Central. Regulation of the Hypothalamic-Pituitary-Adrenocortical Stress ResponseWhen the Glands Produce Too Much
Overproduction by the adrenal glands takes different forms depending on which hormone is involved.
Cushing’s Syndrome
Cushing’s syndrome results from prolonged exposure to high levels of cortisol. The cause can be a cortisol-secreting adrenal tumor, an ACTH-secreting pituitary tumor (which is specifically called Cushing’s disease), or long-term use of corticosteroid medications. The clinical picture is distinctive: weight gain concentrated in the face, neck, and abdomen with thin arms and legs, wide purple stretch marks, easy bruising, muscle weakness, and fat pads above the collarbones.
9Endocrinology and Disorders. A Case Report of Cortisol-Secreating Adrenal Adenoma Causing Cushing SyndromeBeyond the visible changes, excess cortisol raises blood sugar, weakens bones, suppresses the immune system, and can cause depression, anxiety, and cognitive problems. Left untreated, Cushing’s syndrome substantially increases the risk of infections, blood clots, and cardiovascular disease. Treatment depends on the cause: surgery for tumors, and a careful taper when the culprit is prescribed steroids.
Primary Aldosteronism
When the cortex overproduces aldosterone, typically from a small adrenal adenoma or from overgrowth of the aldosterone-producing zone, the result is persistent high blood pressure and low potassium. This condition, sometimes called Conn’s syndrome, is one of the most common treatable causes of hypertension. Patients often present with blood pressure that resists multiple medications, and the diagnosis begins with measuring the ratio of aldosterone to renin in the blood.
10Clinical Chemistry. Primary aldosteronism in a patient with an aldosterone-producing adenomaWhat makes primary aldosteronism especially important is that it is underdiagnosed. Many people with hard-to-control blood pressure never get tested for it, even though removing the offending adrenal adenoma or treating with specific medications can normalize blood pressure and resolve the potassium deficit.
Pheochromocytoma
Pheochromocytoma is a rare tumor of the chromaffin cells in the adrenal medulla that pumps out excessive catecholamines. The hallmark symptoms are dramatic: sudden episodes of severe headache, rapid heartbeat, profuse sweating, and dangerously high blood pressure. These episodes can be unpredictable, triggered by anything from physical exertion to certain foods or anesthesia. High circulating catecholamines can damage the heart and brain if untreated.
11PubMed Central. Hypertension in pheochromocytoma: characteristics and treatmentDiagnosis involves measuring catecholamine breakdown products in the blood or urine, followed by imaging to locate the tumor. Some pheochromocytomas are hereditary, linked to genetic syndromes, which means relatives of an affected person sometimes need screening. Surgery is the standard treatment, but the tumor must be managed carefully beforehand with medications that block catecholamine effects to prevent a dangerous blood-pressure crisis during the operation.
12PubMed Central. Paroxysmal Hypertension in Congenital Hypothyroidism: An Unusual Case of PheochromocytomaWhen the Glands Produce Too Little
Addison’s Disease
Primary adrenal insufficiency, or Addison’s disease, occurs when the adrenal cortex is destroyed, most often by the body’s own immune system attacking it. With less cortex functioning, production of both cortisol and aldosterone drops. One of the most recognizable signs is darkening of the skin and mucous membranes, caused by elevated ACTH and melanocyte-stimulating hormone. When cortisol stops providing its normal negative feedback to the pituitary, ACTH production surges, and because ACTH shares a precursor molecule with the hormone that stimulates pigment-producing cells, the skin darkens as a side effect.
13PubMed Central. Addison’s disease presenting with hyperpigmentationOther symptoms include chronic fatigue, weight loss, low blood pressure, salt cravings, nausea, and muscle weakness. These develop gradually, which is why Addison’s disease is often missed until a stressful event like an infection or surgery tips the person into an adrenal crisis, a medical emergency marked by dangerously low blood pressure, severe dehydration, and altered consciousness. Treatment is lifelong hormone replacement with hydrocortisone (for cortisol) and fludrocortisone (for aldosterone), plus education on “sick-day rules” for increasing doses during illness or physical stress.
Steroid-Induced Adrenal Suppression
The more common form of adrenal insufficiency has nothing to do with adrenal disease at all. When you take corticosteroid medications for conditions like asthma, rheumatoid arthritis, or inflammatory bowel disease, the external cortisol suppresses your HPA axis. The pituitary stops sending ACTH, and the adrenal cortex gradually shrinks from disuse. If the medication is stopped abruptly, the adrenals cannot ramp up production quickly enough, and the result is adrenal insufficiency that mimics Addison’s disease.
This risk is not limited to high doses or long courses. Research has shown that even short courses of steroids lasting fewer than four weeks, as well as low-dose treatment equivalent to less than 5 mg of prednisone per day, can suppress the HPA axis. Inhaled, topical, nasal, and injected steroids carry risk as well, not only oral forms.
14PubMed Central. Glucocorticoid Withdrawal-An Overview on When and How to Diagnose Adrenal Insufficiency in Clinical PracticeThis is why doctors taper corticosteroid prescriptions rather than stopping them suddenly. The taper gives the HPA axis time to wake back up and the adrenal glands time to resume normal cortisol production. Anyone who has been on steroids for more than a few weeks should be aware of this and should never discontinue the medication on their own.
Congenital Adrenal Hyperplasia
Congenital adrenal hyperplasia (CAH) is a group of inherited conditions where one of the enzymes needed to make cortisol from cholesterol is missing or impaired. The most common form involves a deficiency of 21-hydroxylase. Because cortisol cannot be made efficiently, the pituitary keeps sending more ACTH in an attempt to push production higher. That relentless stimulation causes the adrenal glands to enlarge and forces steroid precursors to pile up behind the enzymatic block. Those precursors get diverted into pathways that produce excess androgens.
15Biology and management. Congenital adrenal hyperplasia: 21-hydroxylase deficiency and 11-hydroxylase deficiencyIn the classic, severe form of CAH, the androgen excess can cause ambiguous genitalia in newborn girls and dangerously low cortisol and aldosterone, leading to salt-wasting crises in the first weeks of life. Milder, “nonclassical” forms may not be recognized until later in life, when excess androgens cause symptoms like early pubic hair, acne, irregular periods, or difficulty conceiving.
16Balkan Journal of Medical Genetics. A p.P30L Mutation at the CYP21A2 Gene in Macedonian Patients with Nonclassical Congenital Adrenal HyperplasiaTreatment for classic CAH involves replacing the missing cortisol (and aldosterone, when needed), which also brings ACTH back down and reduces the excess androgen production. The challenge is that slightly too much replacement suppresses growth in children, while slightly too little allows androgens to surge again. Managing CAH is a lifelong balancing act that requires regular monitoring.
Adrenal Incidentalomas
As CT scans and MRIs have become routine for investigating all sorts of medical complaints, doctors increasingly stumble across adrenal masses that were never suspected. These are called incidentalomas, defined as adrenal masses at least 1 cm in size found on imaging done for an unrelated reason. Their prevalence has risen simply because we now scan more people more often, particularly older adults.
17PubMed Central. The Landmark Series: Evaluation and Management of Adrenal IncidentalomasMost incidentalomas turn out to be benign and hormonally inactive, essentially harmless lumps. But a meaningful minority are hormonally active, quietly producing excess cortisol, aldosterone, or catecholamines, or, rarely, are cancerous. Every incidentally discovered adrenal mass therefore needs evaluation for both hormonal function and malignant potential, typically involving blood and urine hormone tests along with a careful look at the imaging characteristics of the mass itself.
18European Journal of Endocrinology. European Society of Endocrinology clinical practice guidelines on the management of adrenal incidentalomas, in collaboration with the European Network for the Study of Adrenal TumorsGuidelines recommend a multidisciplinary approach involving endocrinologists, radiologists, and sometimes surgeons, because the decision of whether to operate, watch, or simply reassure the patient depends on factors that cross specialty lines.
19PubMed. Diagnosis, Management, and Follow-Up of the Incidentally Discovered Adrenal Mass: CUA Guideline Endorsed by the AUAEnvironmental Chemicals and Adrenal Function
Emerging research is examining how industrial chemicals might disrupt normal adrenal function. Endocrine-disrupting chemicals, a broad category that includes pesticides, flame retardants, plasticizers, and certain industrial solvents, can interfere with hormone production throughout the body, and the adrenal glands are no exception.
Animal studies have shown that chronic exposure to brominated flame retardants, chemicals found in electronics, furniture, and building materials, can increase adrenal gland weight and raise levels of corticosterone, the main stress hormone in rodents. These chemicals also appear to alter the activity of enzymes involved in steroid production within the adrenal cortex.
20PubMed Central. Effects of Endocrine-Disrupting Chemicals on Adrenal FunctionTranslating animal findings to human health is always tricky, and much of this research is still in early stages. But the adrenal glands are particularly vulnerable targets for endocrine disruptors because they accumulate lipid-soluble compounds and have a rich blood supply that exposes them to whatever is circulating in the body. As our understanding of how these chemicals interact with steroid-producing pathways deepens, it could change how we think about unexplained adrenal dysfunction in people with high environmental exposures.