Your adrenal glands are two small, triangular organs that sit on top of each kidney. Despite weighing only about 5 grams each, they produce hormones that control blood pressure, metabolism, stress responses, and sex hormone production. Nearly every system in your body depends on at least one hormone made by these glands.
Two Distinct Parts, Different Jobs
Each adrenal gland has two main regions that function almost like separate organs. The outer layer, called the cortex, makes up about 80% of the gland and produces three classes of hormones. The inner core, called the medulla, produces the hormones behind your fight-or-flight response.
The cortex itself is organized into three layers, each responsible for a different hormone type. The outermost layer produces aldosterone, which regulates blood pressure. The middle layer produces cortisol, your primary stress and metabolism hormone. The innermost layer produces androgens, which are precursors to sex hormones like testosterone and estrogen.
Cortisol: Your Stress and Energy Hormone
Cortisol is probably the most well-known adrenal hormone, and for good reason. It controls how your body uses sugar for energy, influences your immune system, and helps you respond to physical and emotional stress. When you’re under pressure, cortisol triggers your liver to release stored glucose into your bloodstream for quick energy. It also signals your pancreas to decrease insulin and increase glucagon, both of which raise blood sugar levels so your muscles and brain have fuel available.
Cortisol follows a predictable daily rhythm. Levels peak in the early morning, typically between 10 and 20 micrograms per deciliter around 6 to 8 a.m., then gradually drop throughout the day to about 3 to 10 micrograms per deciliter by 4 p.m. This pattern is why you naturally feel more alert in the morning and wind down in the evening.
In short bursts, cortisol actually boosts your immune system by limiting inflammation. But when cortisol stays elevated for long periods, the opposite happens. Your body adjusts to the constant exposure, and inflammation increases while immune defenses weaken. This is one reason chronic stress takes a measurable toll on health.
How Your Brain Controls Cortisol Release
Your adrenal glands don’t decide on their own when to release cortisol. They take orders from a signaling chain that starts in your brain. When your hypothalamus detects stress, it releases a chemical messenger that travels to your pituitary gland. The pituitary then sends its own signal down to the adrenal cortex, telling it to produce cortisol.
Once cortisol levels rise high enough, the system shuts itself off. Cortisol signals back to the hypothalamus to stop the chain reaction. This negative feedback loop is designed to be precise, keeping cortisol within a healthy range. When this loop breaks down, whether from chronic stress, tumors, or certain medications, cortisol levels can stay too high or drop too low, both of which cause significant problems.
Aldosterone and Blood Pressure
Aldosterone is the hormone responsible for fine-tuning your blood pressure on a moment-to-moment basis. It works primarily in the kidneys, where it tells specialized cells to reabsorb sodium from urine back into the bloodstream. When sodium levels rise in your blood, your body retains more water to keep concentrations balanced. More water means more blood volume, which raises blood pressure. At the same time, aldosterone causes your kidneys to release potassium through urine, keeping the balance between these two minerals tightly controlled.
This process is part of a larger system involving the kidneys, liver, and adrenal glands working together. When your blood pressure drops or your kidneys detect low sodium, a cascade of chemical signals ultimately triggers the adrenal glands to release more aldosterone. The result is a finely tuned system that adjusts blood pressure continuously throughout the day without you ever being aware of it.
The Fight-or-Flight Response
The inner part of the adrenal gland, the medulla, produces adrenaline and noradrenaline. These are the hormones that kick in during moments of acute danger or excitement, and their effects are almost instantaneous.
When these hormones flood your bloodstream, your body undergoes a rapid transformation:
- Heart: Beats harder and faster, pushing more oxygenated blood to your muscles. Blood pressure spikes.
- Eyes: Pupils dilate to let in more light, sharpening your awareness of your surroundings.
- Muscles: Receive increased blood flow and oxygen, allowing faster and stronger movement.
- Liver: Converts stored glycogen into glucose, flooding the bloodstream with quick energy.
- Skin: Turns pale as blood vessels redirect flow away from the surface and toward muscles and vital organs.
This entire response evolved to help you survive physical threats. In modern life, the same system activates during a car accident, a heated argument, or even a startling loud noise. The response fades once your nervous system determines the threat has passed.
Adrenal Androgens and Sex Hormones
The innermost layer of the adrenal cortex produces a hormone called DHEA and its related forms. These aren’t active sex hormones themselves, but your body converts them into testosterone and estrogen in other tissues. The contribution is significant, especially for women. In premenopausal women, 40 to 75% of circulating testosterone comes from adrenal-produced DHEA. After menopause, over 90% of a woman’s estrogen is derived from it.
In men with normally functioning testes, the adrenal contribution to testosterone is minimal, less than 5%. But adrenal androgens become critical if testicular function is impaired. These hormones also play a key role during puberty, when the adrenal glands ramp up androgen production in a process called adrenarche, contributing to early development of body hair and other changes before the sex organs fully take over hormone production.
What Happens When Adrenal Function Goes Wrong
Because the adrenal glands influence so many systems, problems with overproduction or underproduction of hormones create widespread symptoms.
Too Much Cortisol
Cushing’s syndrome develops when cortisol levels stay elevated for a prolonged period. The signs are often visible: weight gain concentrated in the face, neck, and trunk, while the arms and legs become thinner due to muscle wasting. Wide purple stretch marks may appear on the abdomen, breasts, and hips. Bruising happens easily. Children with the condition tend to gain weight while growing more slowly than their peers. Women may develop excess facial and body hair, and menstrual periods can become irregular or stop entirely. Men may experience reduced fertility and lower sex drive.
Too Little Cortisol
Adrenal insufficiency, sometimes called Addison’s disease, occurs when the adrenal glands don’t produce enough cortisol or aldosterone. Symptoms develop gradually and include extreme fatigue, unintentional weight loss, low blood pressure, salt cravings, and darkening of the skin. Because aldosterone may also be low, people with this condition can become dangerously dehydrated and develop electrolyte imbalances. Without treatment, a sudden physical stress like an infection or injury can trigger an adrenal crisis, a medical emergency where blood pressure drops to life-threatening levels.
Aldosterone Imbalances
Overproduction of aldosterone causes the kidneys to retain too much sodium and water while flushing out too much potassium. The result is high blood pressure that resists standard treatments, along with muscle cramps, weakness, and frequent urination. Underproduction leads to low blood pressure, dehydration, and dangerously high potassium levels.