The pituitary gland produces and releases hormones that control some of your body’s most essential functions, including growth, metabolism, reproduction, stress response, and water balance. Despite weighing only about half a gram, this pea-sized gland acts as a central command center, sending chemical signals to other glands and organs throughout the body.
Where the Pituitary Gland Sits
The pituitary gland is located at the base of your brain, behind the bridge of your nose and directly below a brain region called the hypothalamus. It rests in a small bony pocket of the skull called the sella turcica. In an average adult, the gland measures roughly 13 mm across, 9 mm front to back, and 6 mm tall.
The gland has two distinct lobes that work differently. The front lobe (anterior pituitary) is the larger of the two and connects to the hypothalamus through a specialized network of blood vessels. The back lobe (posterior pituitary) connects to the hypothalamus through nerve fibers instead. This structural difference matters because it changes how each lobe receives its instructions and delivers its hormones.
How the Hypothalamus Controls the Pituitary
The pituitary gland doesn’t act on its own. It takes orders from the hypothalamus, a brain region that monitors conditions throughout your body and decides when hormone levels need adjusting. Specialized nerve cells in the hypothalamus release tiny amounts of “releasing hormones” or “inhibiting hormones” into a dedicated set of blood vessels that flow directly down to the front lobe of the pituitary. These chemical messages tell the pituitary to either ramp up or dial back production of specific hormones.
This creates a feedback loop. When hormone levels in the blood rise high enough, the hypothalamus detects the change and reduces its stimulating signals. When levels drop too low, it sends more. This back-and-forth communication keeps your body’s hormone levels within a tight range, and it’s why the hypothalamus and pituitary are often described as a single unit: the hypothalamic-pituitary axis.
Hormones From the Front Lobe
The anterior pituitary produces six major hormones, each targeting a different organ or system.
Growth Hormone
Growth hormone does more than drive childhood height. In adults, it increases protein building in tissues, boosts fat breakdown and oxidation (which reduces total body fat), and raises energy expenditure partly by increasing lean body mass. It also influences how the body handles carbohydrates and can affect sodium balance. Growth hormone works both directly on tissues and indirectly by triggering the liver to produce another growth-promoting signal.
Thyroid-Stimulating Hormone
This hormone tells your thyroid gland to produce and release its own hormones, which set your body’s metabolic rate. Too little thyroid stimulation slows metabolism down, causing fatigue, weight gain, and cold sensitivity. Too much speeds it up, leading to weight loss, anxiety, and a racing heart.
ACTH (The Stress Hormone Trigger)
ACTH travels to your adrenal glands, which sit on top of your kidneys, and tells them to produce cortisol. Cortisol helps your body respond to stress, regulates blood sugar, controls inflammation, and influences blood pressure. When the pituitary overproduces ACTH, cortisol levels climb too high, a condition known as Cushing’s disease.
FSH and LH (The Reproductive Hormones)
These two hormones work as a team to regulate the reproductive system. In females, FSH stimulates follicles on the ovaries to grow and prepare eggs for release. As those follicles grow, they produce estrogen and a small amount of progesterone. Around day 14 of the menstrual cycle, a sudden surge of LH triggers the mature follicle to rupture and release its egg. LH also prompts the ovaries to produce progesterone, which supports early pregnancy.
In males, FSH and LH together trigger the testes to produce testosterone, the hormone responsible for body hair growth, voice deepening, and sperm production. FSH specifically stimulates sperm production, while LH drives testosterone output. Both are needed to sustain normal fertility.
Prolactin
Prolactin’s most recognized role is stimulating breast milk production after childbirth. But it also influences menstrual cycles, fertility, and sexual function in both sexes. Normal prolactin levels in non-pregnant adults are below 25 ng/mL for females and below 20 ng/mL for males.
Hormones From the Back Lobe
The posterior pituitary doesn’t actually manufacture its own hormones. Instead, nerve cells in the hypothalamus produce two hormones and send them down nerve fibers into the back lobe, where they’re stored until needed.
The first is antidiuretic hormone (ADH), which controls how much water your kidneys reabsorb. When you’re dehydrated, ADH levels rise and your kidneys hold onto more water, producing less and more concentrated urine. When you’ve had plenty of fluids, ADH drops and your kidneys let more water pass through.
The second is oxytocin. In females, oxytocin causes the uterus to contract during labor and triggers breast milk to flow during nursing. It also plays a role in parent-infant bonding. In males, oxytocin contributes to bonding with children and plays a part in ejaculation by contracting the tube that carries sperm forward.
What Happens When the Pituitary Malfunctions
Pituitary problems usually come down to producing too much or too little of one or more hormones. The most common cause is a pituitary adenoma, a usually benign tumor that grows on the gland. About half of these tumors actively produce excess hormones, while the other half are “nonfunctioning” and cause problems mainly by pressing on surrounding tissue as they grow.
Prolactin-secreting tumors (prolactinomas) are the most common type, accounting for roughly 30% of all pituitary tumors. They can cause unexpected milk production from the breasts, irregular periods, and fertility problems. Tumors that overproduce ACTH lead to Cushing’s disease, which causes upper body weight gain, a rounded face, thinning skin, stretch marks, high blood pressure, high blood sugar, and muscle weakness. Tumors that overproduce growth hormone cause acromegaly in adults, where the hands, feet, and facial features gradually enlarge, often accompanied by high blood pressure and diabetes.
When the pituitary produces too little of its hormones, the condition is called hypopituitarism. This can result from tumors pressing on healthy pituitary tissue, from surgery to remove a tumor, or from other causes like head injury or radiation. Because the pituitary controls so many other glands, losing its output can affect the thyroid, adrenal glands, and reproductive organs simultaneously. Treatment typically involves replacing the missing hormones that the downstream glands would normally produce.
How Pituitary Function Is Tested
Simple blood tests can measure levels of pituitary hormones and the hormones produced by their target glands. If baseline levels look abnormal, doctors may use stimulation tests to see how the pituitary responds under pressure. One common approach delivers a small dose of a stimulating substance and then measures whether cortisol rises appropriately, which checks the connection between the pituitary and the adrenal glands. A water deprivation test, where fluid intake is restricted while urine concentration is monitored, can reveal whether ADH is working properly.
If blood work suggests a pituitary problem, imaging with an MRI provides a detailed look at the gland and surrounding structures, and can identify tumors as small as a few millimeters.