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Not all pituitary tumors (pituitary adenomas) cause symptoms. But when they do, they can cause symptoms in these ways:
The pituitary gland sits in a very small space at the base of the skull. Pituitary tumors that grow large enough can press on or grow into nearby parts of the brain, nerves involved with vision, or other important structures. This can lead to symptoms such as:
Tumors that grow large enough can also press on and destroy the normal parts of the pituitary gland. This can lead to low levels of one or more pituitary hormones, which can in turn lead to low levels of some body hormones such as cortisol, thyroid hormone, and sex hormones. Depending on which hormones are affected, symptoms might include:
Large tumors can sometimes press on the posterior (back) part of the pituitary, causing a shortage of the hormone vasopressin (also called anti-diuretic hormone or ADH). This can lead to diabetes insipidus. In this condition, too much water is lost in the urine, so the person urinates often and becomes very thirsty as the body tries to keep up with the loss of water.
If left untreated, this can cause dehydration and altered blood mineral levels, which can lead to coma and even death. Diabetes insipidus can be treated by replacing vasopressin with a drug called desmopressin. (Diabetes insipidus is not related to diabetes mellitus, in which people have high blood sugar levels.)
Another way that a pituitary tumor (especially a larger one) can cause many of the symptoms above is if it leads to bleeding or a blockage in a blood vessel, reducing the blood supply to the pituitary. This condition, known as pituitary apoplexy, isn’t common, but it can result in symptoms developing quickly, and it's often a medical emergency.
Symptoms from excess pituitary hormones depend on which hormone(s) the tumor is making. (Even when a tumor makes excess hormones, it might still cause some of the symptoms above, such as vision changes or headaches.)
The effects of tumors making too much growth hormone (GH) are different in children and teens from those in adults.
In children and teens, high GH levels can stimulate the growth of nearly all bones in the body, which is known as gigantism. Signs and symptoms can include:
In adults, the arm and leg bones can’t grow any more, even when GH levels are very high, so people don’t grow taller. But the bones in an adult's hands, feet, and skull can grow throughout life. Making too much GH as an adult causes a condition called acromegaly. Signs and symptoms can include:
Many of these changes can occur very slowly, and people might not notice them until they look at an old picture of themselves or try to put on a hat, ring, gloves, or shoes they haven’t worn in many years.
High ACTH levels cause the adrenal glands to make excess steroid hormones such as cortisol. This causes symptoms that doctors group together as Cushing’s disease. In adults, the symptoms can include:
Most of these symptoms can also occur in children. Children with Cushing’s disease may also stop growing and have problems with school performance.
Prolactinomas are most common in young women and older men.
These tumors can also sometimes grow large enough to press on nearby nerves and parts of the brain, which can cause headaches and vision problems. In females who don’t have periods (such as girls before puberty and women after menopause), prolactinomas might not be noticed until they grow large enough to cause these symptoms.
These rare tumors make too much thyroid-stimulating hormone (TSH), which then causes the thyroid gland to make excess amounts of thyroid hormones. This can cause symptoms of hyperthyroidism (overactive thyroid), such as:
These tumors make luteinizing hormone (LH) and/or follicle-stimulating hormone (FSH).
Most gonadotropin-secreting adenomas don’t make enough hormones to cause symptoms, so they are basically non-functional adenomas. These tumors may grow large enough to cause symptoms such as headaches and vision problems before they are found. (See "Symptoms caused by larger tumors" above.)
By pressing on the rest of the pituitary, these tumors can also sometimes result in lower levels of sex hormones such as estrogen, progesterone, and testosterone. This can lead to irregular menstrual periods in women or erectile dysfunction and decreased interest in sex in men.
Less often, gonadotroph adenomas do make excess hormones, resulting in higher levels of sex hormones. Most of these tumors occur in middle-aged adults, and the higher levels of hormones don’t usually result in any symptoms. But they might cause problems in younger people, such as irregular menstrual periods in younger women or early signs of puberty in girls.
The American Cancer Society medical and editorial content team
Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.
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Last Revised: October 10, 2022
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