Pituitary tumors are atypical growths that develop in the pituitary gland. They are typically noncancerous. Doctors often use blood tests as a first step in diagnosing pituitary tumors.

The pituitary gland is a tiny, pea-sized gland at the base of the brain. It is part of the endocrine system and helps control the release of hormones from other endocrine glands, such as the adrenal glands, sex glands, and thyroid. It also releases hormones affecting body tissues, such as breast milk glands and bones.

Some pituitary tumors can cause the pituitary gland to make excessive amounts of hormones, while others can cause the pituitary gland to make too little. Imbalances in hormones can cause various problems in many body systems.

In this article, we examine blood tests for pituitary tumors. We discuss what the blood tests look for, the types of blood tests for different tumors, and other tests doctors may use to diagnose pituitary tumors.

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If a doctor suspects a person has a pituitary tumor, they will order blood tests to check for too much or too little levels of a specific hormone.

Pituitary tumors that secrete hormones are called functional pituitary adenomas. Functional adenomas can lead to extra amounts of one or more hormones.

Nonfunctional adenomas are growths that do not secrete hormones but may grow large enough to inhibit the production of hormones, causing low levels of certain hormones.

Blood tests for pituitary tumors look for abnormally high or low levels of:

  • growth hormone (GH) and insulin-like growth factor 1 (IGF-1)
  • thyroid stimulating hormone (TSH) and thyroid hormones
  • adrenocorticotropic hormone (ACTH) and cortisol
  • luteinizing hormone (LH), testosterone, and estrogen
  • follicle stimulating hormone (FSH)
  • prolactin

High levels of one or more of these hormones may suggest a person has a functional adenoma. Low levels may indicate a nonfunctional adenoma.

There are several types of pituitary tumors. A doctor can diagnose the specific type depending on which hormones display elevated or reduced levels in a blood test.

The types of pituitary tumors and their corresponding blood tests are as follows:

A lactotroph adenoma is a prolactin-secreting tumor. Prolactin is a hormone that causes breasts to grow and produce milk during pregnancy and after birth.

Lactotroph adenomas can produce too much prolactin, which may cause breast milk production in people who are not pregnant or breastfeeding. It may also cause:

  • menstrual problems
  • fertility issues
  • low sex drive

If a doctor suspects a person has a lactotroph adenoma, they will likely order a prolactin test to measure prolactin levels in the blood. They may also check blood levels of other hormones, since other pituitary tumor types may also cause rises in prolactin levels.

A somatotroph adenoma is a GH-secreting tumor. The hormone GH is essential for:

  • normal growth
  • fat distribution
  • helping manage sugar and fat levels in the body
  • bone and muscle strength

GH stimulates the liver to release IGF-1, which works on multiple tissues to promote growth.

Imbalances in GH levels affect children and teenagers differently than adults. In children and teenagers, excessive GH levels stimulate bone growth throughout the body, known as gigantism.

In adults, high GH levels cannot cause arm and leg bones to grow further, so people do not grow taller. However, high GH levels can make the hands, feet, and skull bones grow, which causes a condition known as acromegaly.

GH vs. IGF-1

If a doctor suspects someone has a somatotroph adenoma, they will likely order a blood test to check IGF-1 levels in the blood.

Doctors could also measure a person’s blood GH levels. However, testing IGF-1 levels is usually more helpful than testing GH levels because the IGF-1 level does not change significantly throughout the day, but the GH level can change.

Elevated IGF-1 levels may indicate increased GH production, signaling a somatotroph adenoma.

A corticotroph adenoma is a tumor that secretes adrenocorticotropic (ACTH). ACTH controls the production and release of a hormone called cortisol from the adrenal gland.

Most symptoms associated with ACTH-secreting tumors occur due to elevated cortisol levels. Too much cortisol can lead to Cushing’s syndrome, with symptoms such as:

  • fat buildup in certain body areas
  • rapid weight gain
  • high blood pressure

If a doctor suspects a person has high cortisol levels in the body, called hypercortisolism, they will order a blood, saliva, or urine test. If these test results suggest hypercortisolism, ACTH levels will need measuring. Elevated ACTH from corticotroph adenoma will require further confirmatory testing.

A thyrotroph adenoma is a thyrotropin-secreting tumor. Thyrotropin (TSH) controls the production and release of the thyroid hormones triiodothyronine (T3) and thyroxine (T4) by the thyroid gland.

T3 and T4 help regulate:

  • metabolism
  • energy levels
  • body weight

Thyrotroph adenomas cause the thyroid gland to produce excessive thyroid hormone, resulting in an overactive thyroid, called hyperthyroidism. Some symptoms of hyperthyroidism include:

  • nervousness
  • increased sweating
  • tremors
  • insomnia
  • frequent bowel movements

Learn more about hyperthyroidism here.

Doctors may order one or more blood tests to assess a person’s thyroid function. These may include tests to measure TSH, T3, and T4 levels.

Thyrotroph adenomas are a rare cause of hyperthyroidism. They account for less than 1% of pituitary tumors.

A gonadotroph adenoma is a tumor that secretes gonadotropin hormones called FSH and LH. FSH and LH regulate ovarian and testicular function, which is essential for:

  • normal growth
  • sexual development
  • reproduction

Gonadotropin-secreting tumors typically do not produce enough hormones to cause symptoms. Doctors may still run blood tests to look for high levels of LH and FSH if they suspect a person has one. They may also check the levels of related hormones, such as:

  • testosterone
  • estrogen
  • progesterone

These tumors are very rare.

Nonfunctional pituitary adenomas do not usually make enough hormones to cause symptoms.

Sometimes pituitary hormones in the blood may still be higher than normal. They can also be lower than normal if the tumor is large enough to press on the pituitary cells that typically make those hormones.

Checking blood hormone levels could help diagnose nonfunctioning adenomas.

Medical history and physical examination provide important information that may lead doctors to suspect pituitary tumors.

Alongside blood tests, doctors use other diagnostic tests for pituitary tumors. Depending on the tumor type, they may use tests such as:

  • vision testing
  • urine tests
  • late-night salivary cortisol
  • 24-hour urinary cortisol excretion
  • petrosal sinus sampling
  • MRI scan
  • CT scan

Pituitary tumors are noncancerous growths that occur in the pituitary gland. Doctors use many tests to diagnose a pituitary tumor depending on a person’s symptoms and the type of tumor they suspect.

Generally, pituitary tumors can cause an increase or decrease in specific hormone levels, depending on whether tumors are functional or nonfunctional.

As part of the diagnostic process, doctors use a variety of blood tests to look for hormone imbalances. They may look for too high or too low levels of:

  • GH and IGF-1
  • TSH, T3, and T4
  • ACTH and cortisol
  • LH and FSH
  • sex hormones, testosterone, estrogen, and progesterone
  • prolactin

Doctors may use other tests, such as urine tests, salivary tests, and MRI scans, alongside blood tests to confirm a diagnosis.