Most pituitary tumors are benign growths called adenomas, and they cause symptoms in two main ways: by pressing on nearby structures in the brain, or by disrupting hormone levels. Many people with small pituitary tumors have no symptoms at all. Pooled data from autopsy and imaging studies suggest that roughly 15 to 22 percent of the general population has a pituitary tumor they never know about. When symptoms do appear, they depend on the tumor’s size and whether it produces excess hormones.
Pituitary tumors smaller than 10 millimeters are classified as microadenomas, while those 10 millimeters or larger are macroadenomas. Microadenomas rarely press on surrounding tissue, so their symptoms tend to come from hormone overproduction. Macroadenomas are large enough to compress the optic nerves, the pituitary gland itself, or nearby brain structures, which produces a different set of problems.
Vision Changes and Pressure Symptoms
The pituitary gland sits just below the optic chiasm, the point where the optic nerves from each eye cross. As a macroadenoma grows upward, it can compress those crossing nerve fibers and block visual information from the outer (temporal) half of each eye’s field of vision. The result is a progressive loss of peripheral vision on both sides. You might not notice it at first because each eye partially compensates for the other, but over time it can feel like looking through a narrow tunnel.
If the tumor presses more on one side than the other, it can cause a blind spot in the center of one eye’s vision along with partial vision loss in the opposite eye. Left untreated, continued compression can lead to significant or permanent vision loss. Some people first discover their tumor after an eye exam reveals unexplained visual field deficits.
Headaches
Large pituitary tumors can cause headaches by stretching the membrane that covers the brain or by pressing on surrounding structures. These headaches are not always distinctive enough to point to a pituitary problem on their own, but they tend to be persistent and may worsen over time as the tumor grows. In some cases, smaller hormone-producing tumors also cause headaches, though the exact mechanism is less clear.
Symptoms From Excess Prolactin
Prolactinomas are the most common type of hormone-producing pituitary tumor. They secrete excess prolactin, a hormone that normally triggers milk production after childbirth. In women, the earliest signs are often irregular menstrual periods or periods stopping altogether, along with milky breast discharge unrelated to pregnancy or breastfeeding. Breast soreness and painful intercourse from vaginal dryness are also common. In both men and women, elevated prolactin can significantly reduce sex drive.
Because menstrual changes prompt earlier medical attention, prolactinomas in women tend to be caught when they are still small. In men, symptoms like decreased libido develop gradually and are easy to attribute to other causes, so the tumor often grows larger before it is detected.
Symptoms From Excess Growth Hormone
A pituitary tumor that overproduces growth hormone in adults causes a condition called acromegaly. The changes are slow and subtle at first, making them easy to miss. Hands and feet gradually enlarge. You might notice your rings feel tighter or you need a wider shoe size. Facial features coarsen over time: the nose, lips, and tongue get larger, the brow and lower jaw become more prominent, and gaps may develop between the teeth.
These skeletal and soft-tissue changes also create internal problems. Thickened tissue in the airway can lead to sleep apnea, causing loud snoring and daytime fatigue. Joint pain, excessive sweating, and skin thickening are also typical. Because the changes happen so gradually, many people only recognize them in hindsight after comparing old photographs.
Symptoms From Excess Cortisol
When a pituitary tumor produces too much of the hormone ACTH, it drives the adrenal glands to flood the body with cortisol. This is called Cushing disease, and it produces a recognizable pattern of physical changes when cortisol levels stay high long enough. Weight collects around the midsection, face, and upper back (sometimes forming a noticeable hump between the shoulders), while the arms and legs stay thin or even lose muscle mass. The face becomes rounder and fuller.
Skin becomes fragile and bruises easily. Wide, purple stretch marks can appear on the abdomen, breasts, hips, and underarms. Muscle weakness, particularly in the upper legs and arms, makes everyday tasks like climbing stairs or lifting things more difficult. Mood changes, high blood sugar, and high blood pressure often accompany these visible signs.
Symptoms From Hormone Deficiency
A growing tumor can also damage the healthy pituitary tissue around it, preventing the gland from producing enough of one or more hormones. This is called hypopituitarism, and its symptoms depend on which hormones are affected.
- Thyroid hormone deficiency: fatigue, weight gain, sensitivity to cold, constipation, and dry skin.
- Sex hormone deficiency: reduced sex drive, fatigue, hot flashes, irregular or absent periods in women, erectile dysfunction in men, and difficulty conceiving. Loss of pubic and body hair can also occur.
- Growth hormone deficiency: in adults, this often shows up as increased body fat, decreased muscle mass, low energy, and reduced sense of well-being. In children, it can delay or prevent puberty and normal growth.
- Cortisol deficiency: fatigue, low blood pressure, nausea, and dizziness, especially during illness or stress.
Because these symptoms overlap with many common conditions, hormone deficiency from a pituitary tumor is often missed for months or years before the real cause is identified.
Pituitary Apoplexy: An Emergency
In rare cases, a pituitary tumor bleeds internally or outgrows its blood supply, a condition called pituitary apoplexy. It comes on suddenly and is potentially life-threatening. The hallmark symptom is a severe, explosive headache, often described as the worst headache of your life. It can be accompanied by sudden vision loss, double vision, nausea, and a rapid drop in blood pressure from the sudden loss of pituitary hormone production. This is a medical emergency that requires immediate treatment.
How Pituitary Tumors Are Found
Many pituitary tumors are discovered incidentally during a brain MRI or CT scan done for an unrelated reason. When symptoms are present, doctors typically start with blood tests to check whether hormone levels are too high or too low. A urine test can help detect excess cortisol in cases of suspected Cushing disease.
MRI is the primary imaging tool for confirming a pituitary tumor, pinpointing its size, and showing whether it is pressing on the optic nerves or other structures. CT scans are used less often but can be helpful when planning surgery. A formal visual field test by an eye specialist can document the extent of any peripheral vision loss and help track changes over time.