A gland is an organ or cluster of cells that produces and releases substances your body needs to function. Some glands release hormones into your bloodstream. Others send their products through tiny tubes called ducts to specific locations, like your skin surface or digestive tract. Together, your glands regulate everything from body temperature and blood sugar to growth, reproduction, and mood.
How Glands Work at the Cellular Level
Glands are made up of specialized clusters of cells, called epithelial cells, that are built to manufacture and release specific substances: proteins, fats, carbohydrates, water, and electrolytes. These cells absorb raw materials from your blood supply, assemble them into the needed product, then push that product out of the cell in one of three ways.
The most common method is a clean handoff: the cell packages its product into a tiny bubble that merges with the cell wall and dumps its contents outside, leaving the cell completely intact. Your sweat glands work this way. A second method involves pinching off a piece of the cell membrane along with the product. Mammary glands use this approach to release breast milk. The third method is the most dramatic: the entire cell fills with its product, ruptures, and dies, spilling everything into the duct. The oil-producing glands in your skin work this way, which is why they constantly need to regenerate new cells.
The Two Main Types of Glands
Every gland in your body falls into one of two categories based on how it delivers its product.
Exocrine Glands
Exocrine glands have ducts, physical tubes that carry their secretions to a specific surface. Your salivary glands send saliva into your mouth through ducts. Your sweat glands push sweat through ducts to the surface of your skin. Other examples include the glands in your stomach lining that release digestive acid, tear glands that keep your eyes moist, and the sebaceous glands that coat your hair and skin with protective oil.
Endocrine Glands
Endocrine glands have no ducts at all. Instead, they release hormones directly into your bloodstream, which carries those chemical messengers to target cells throughout the body. Once a hormone reaches its target, it binds to a specific receptor on or inside the cell, like a key fitting into a lock. That binding triggers changes inside the cell: it might activate certain genes, speed up a chemical reaction, or kick off a chain of signals that alters how the cell behaves. This is how a tiny gland in your brain can control the activity of organs far away in your abdomen or pelvis.
Major Endocrine Glands and What They Do
Your body has several major endocrine glands, each with a distinct role.
The pituitary gland, a pea-sized structure at the base of your brain, is often called the “master gland” because its hormones tell other glands when to ramp up or dial back their own production. It controls growth, metabolism, and reproductive function.
The thyroid gland, located in your neck just below the Adam’s apple, regulates your metabolism, the rate at which your cells convert food into energy. When it produces too little, you feel sluggish, cold, and gain weight easily. When it produces too much, your heart races and you lose weight without trying.
The two adrenal glands sit on top of your kidneys and produce stress hormones like cortisol and adrenaline. They also help regulate blood pressure and salt balance. The pineal gland, located deep in the center of your brain, produces the sleep hormone melatonin. The thymus, in your upper chest, plays a key role in training immune cells during childhood.
The ovaries (located on either side of the uterus) and testes (suspended outside the body in the scrotum) produce sex hormones that drive puberty, fertility, and sexual function.
Some Glands Do Both Jobs
A few organs act as both endocrine and exocrine glands at the same time. The pancreas is the best-known example. It sits behind your stomach and has two completely separate systems running side by side. Its exocrine cells produce digestive enzymes and send them through a duct into your small intestine. Meanwhile, scattered clusters of endocrine cells called islets of Langerhans release hormones directly into the bloodstream. These islets contain at least five different cell types, the most important being the ones that produce insulin (which lowers blood sugar) and glucagon (which raises it). When these endocrine cells malfunction, the result is diabetes.
What Happens When Glands Malfunction
Gland problems generally come down to producing too much or too little of a substance. Overproduction is called hypersecretion, and underproduction is called hyposecretion. Either one can cause significant health problems depending on which gland is affected.
An underactive thyroid, for instance, is one of the most common glandular disorders worldwide. A 2021 global analysis found that endocrine and metabolic disorders affected nearly 476 million people globally, with diabetes, obesity, and thyroid conditions leading the count. The incidence that year alone was roughly 79.5 million new cases. These numbers reflect how central glands are to overall health: when one gland drifts out of balance, the effects ripple through multiple body systems.
Thyroid function is typically checked with a blood test that measures how much thyroid-stimulating hormone (TSH) your pituitary gland is sending out. If the pituitary is calling loudly for more thyroid hormone, your TSH will be high, signaling an underactive thyroid. If it barely needs to ask, your TSH will be low, suggesting an overactive one. Research from the American Thyroid Association suggests that the healthiest outcomes are associated with TSH levels in the middle-to-upper portion of the normal range, paired with free T4 levels in the lower-to-middle range.
Common Exocrine Gland Issues
Exocrine glands cause their own set of familiar problems. Blocked or overactive sebaceous glands contribute to acne. Dry eye occurs when your tear glands don’t produce enough fluid. Salivary gland stones can block a duct and cause painful swelling in your jaw. Cystic fibrosis, a genetic condition, causes exocrine glands throughout the body to produce abnormally thick, sticky secretions that clog the lungs and digestive tract.
Sweat gland disorders range from excessive sweating (hyperhidrosis) to virtually no sweating at all, which can be dangerous because it removes your body’s primary cooling mechanism. The pancreas’s exocrine side can also fail, leading to poor fat digestion and nutrient absorption when it stops producing enough digestive enzymes.
How Glands Communicate With Each Other
Your endocrine glands don’t work in isolation. They form an interconnected signaling network where one gland’s output influences another. The hypothalamus, a region at the base of your brain, acts as the bridge between your nervous system and your endocrine system. It sends signals to the pituitary gland, which in turn sends hormones to the thyroid, adrenals, and reproductive organs. Those glands then report back: when hormone levels rise high enough, the pituitary receives the signal and dials down its stimulation. This feedback loop keeps hormone levels within a tight range.
This layered communication system is why a single gland problem can produce symptoms that seem unrelated. A pituitary tumor, for example, can disrupt thyroid function, adrenal output, and reproductive hormones all at once, because it sits at the top of the command chain. Understanding that glands operate as a network, not as isolated organs, helps explain why doctors sometimes need to test several hormone levels to pinpoint the source of a problem.