Pituitary disorders



Last Review Date: August 8, 2017


What are they?

Pituitary disorders are characterised by excess amounts of, or a deficiency in, one or more of the hormones produced by the pituitary gland and/or by the symptoms caused by the compression of the surrounding tissues when a pituitary tumour is present. The pituitary is a pea-sized gland located in the centre of the head behind the sinus cavity. It is found at the bottom of the brain, below the hypothalamus.

The hypothalamus and pituitary gland are part of the endocrine system - a group of glands that work together to produce and regulate hormones that affect tissues throughout the body. The hypothalamus communicates with the brain and nervous system. It senses the body’s need for a specific hormone and tells the pituitary when to initiate or increase production of that hormone.

The pituitary consists of an anterior and posterior portion. In the anterior (or front) portion, growth hormone (GH), adrenocorticotrophin (ACTH), thyroid-stimulating hormone (TSH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), and prolactin are produced. These hormones help regulate bone growth, muscle mass, the body’s response to stress, blood sugar, the rate at which the body uses energy (metabolic rate), the development of secondary sexual characteristics, fertility and milk production. They affect specific ‘target’ tissues throughout the body, including the thyroid gland, adrenal glands, ovaries (women) and testes (men).

In the posterior (or rear) portion of the pituitary, oxytocin is produced and antidiuretic hormone (ADH, produced in the hypothalamus) is stored for release. ADH controls the amount of water that the kidneys excrete, which in turn helps regulate the balance of water in the body. Oxytocin stimulates the contraction of the uterus during and after childbirth and is responsible for stimulating the release of milk during breastfeeding.


What can go wrong?

The most common problem with the pituitary is the development of a tumour. While most tumours are benign, they can produce excessive amounts of a specific pituitary hormone, crowd out the production of other hormones and compress surrounding tissues. Blood vessels and the optic nerves (the nerves connecting the back of each eye with the brain) are in close proximity to the pituitary gland, and pressure from a tumour can cause headaches, visual disturbances, loss of vision, fatigue, weakness and seizures, as well as a host of signs and symptoms related to diminished hormone production.

Other pituitary disorders can arise from inherited genetic mutations; others are congenital, due to trauma or an impaired blood supply, due to surgical or radiation treatment of a previous pituitary disorder, due to a malignant tumour (rare), or due to causes that are not yet well understood. The hormone deficiencies and excesses from these disorders can produce a variety of symptoms depending on which hormones and target tissues are affected.

When the hypothalamus is dysfunctional, pituitary hormone production is often affected. Excess or deficient hormone production by the pituitary may also occur if the glands ‘downstream’ from it are dysfunctional. For example, the hypothalamus normally detects thyroid hormone deficiency in the blood and stimulates the pituitary to produce TSH. TSH, in turn, stimulates thyroid hormone production by the thyroid gland. If the thyroid gland is dysfunctional and cannot produce adequate amounts of this hormone, blood thyroid hormone levels will remain below normal even though the hypothalamus and pituitary are promoting production. The result is excessive amounts of TSH and deficient thyroid hormone.

Examples of common pituitary disorders

  • Pituitary tumours. These may be hormone-secreting or non-secreting tumours and they are benign. They may cause visual disturbances and headaches as they grow and compress surrounding tissues, and they often result in excessive amounts of one pituitary hormone and decreasing amounts of the other hormones.
  • Growth hormone deficiency. This has a variety of causes. In children, it causes delayed growth and short stature; in adults, it can lead to muscular weakness, fatigue, decreased bone mass and obesity.
  • Hypopituitarism. This has a variety of causes, including tumours, trauma, decreased pituitary blood supply, infection, sarcoidosis, an autoimmune process, radiation, surgical removal of the pituitary, or a side effect of pituitary surgery. It results in a general decrease in pituitary hormone production.
  • Hyperprolactinaemia. This is either a pituitary tumour that secretes prolactin or a tumour that prevents the regulation of prolactin production. It can cause galactorrhoea, amenorrhoea, and decreased sex drive in men.
  • Empty sella syndrome. The sella (which is the structure that surrounds the pituitary gland) may increase in size and put pressure on the pituitary gland. In rare cases, the gland shrinks and hormone production decreases, leading to hypopituitarism.

Examples of rare pituitary disorders

  • Acromegaly and gigantism. This results in excess growth hormone production, usually due to a tumour. When it occurs in childhood, it causes gigantism associated with excessive bone growth and abnormally tall stature; in adults, it causes acromegaly, increased bone thickness, coarsened facial features, enlarged hands and feet, carpal tunnel syndrome, headaches, sweating, sleep apnoea, fatigue and hypertension.
  • Cushing’s disease. The symptoms of Cushing’s syndrome are caused by a pituitary tumour that produces excess ACTH, which leads to excess exposure to cortisol (the adrenal gland hormone). Symptoms vary, but they include: upper body obesity, a rounded face, thin skin, pink streaks on the abdomen, muscular weakness, osteoporosis, high blood sugar, and high blood pressure.
  • Diabetes insipidus. This is caused by decreased production of ADH by the hypothalamus. The patient’s kidneys do not conserve water and concentrate urine, meaning that the patient is thirsty and has frequent dilute urination.
  • Nelson’s syndrome. A pituitary tumour develops that produces ACTH and can cause darkening of the skin. Patients may develop this syndrome when adrenal glands are removed as part of the treatment for Cushing’s disease.
  • Multiple endocrine neoplasia Type 1 (MEN1). This is an inherited genetic mutation that increases the risk of developing tumours in the pituitary.
  • Kallman syndrome. A deficient release of GnRH (gonadotropin-releasing hormone) leads to a lack of FSH and LH production, which causes delayed or absent puberty. It is associated with no sense of smell and occurs only in males.
  • Pituitary infarction. This results in restricted blood supply to the pituitary gland, which may cause gland tissue damage and lead to hypopituitarism.
  • Sheehan syndrome. The pituitary gland increases in size during pregnancy, which can cause pituitary infarction if there is an acute drop in blood pressure during childbirth.
  • Craniopharyngioma. This is the most common tumour that develops close to the pituitary gland in children. It is benign but it may put pressure on the pituitary, causing hypopituitarism, headaches, visual disturbances and delayed growth.

Tests

Tests are performed to detect excess or deficient hormone production, determine the cause and evaluate the severity of the condition. Testing frequently includes both the hormones that the pituitary produces (such as TSH) and the hormones of other endocrine glands that the pituitary is responsible for stimulating (such as the thyroid gland hormone thyroxine). Since pituitary hormones are released as needed, concentrations may be relatively constant in the blood (such as TSH); vary over the course of a day (such as GH); vary over a cycle (such as FSH and LH during the menstrual cycle); or be present in specific situations (such as prolactin in a lactating woman or ACTH as a response to a physical or emotional stress). This may lead to the need for suppression or stimulation challenge tests. Medications are given to stimulate or suppress hormone production so that the change can be measured. It may also lead to related tests, such as the test to measure IGF-1 (insulin-like growth factor-1), which reflects total growth hormone (GH) production, along with the test to measure GH.

Testing may be used to help diagnose a pituitary disorder and may be ordered at intervals to monitor the effectiveness of treatment. Long-term monitoring may be necessary in some cases because treatment may not completely resolve the condition; some treatments may cause additional pituitary dysfunction in the present (e.g., surgery) or in the future (e.g., radiation); and some inherited conditions may present a lifetime risk of developing a pituitary disorder.

Laboratory tests

Non-laboratory tests


Treatment

Treatment varies depending on what caused the pituitary disorder. Medications may be used to block hormone action, supplement missing or deficient hormones, and shrink pituitary tumours (to reduce compression symptoms and sometimes prior to surgery). When a pituitary tumour is present, a patient may undergo surgery to remove the tumour, or to remove most of the tissue when all of it cannot be removed. The pituitary gland is accessed through the nose (transsphenoidal surgery). The procedure is delicate and requires an experienced surgeon. Targeted radiation therapy may be used in conjunction with other treatments to decrease the size of the tumour and reduce excess hormone production.

Patients should work with their doctor and/or an endocrinologist (a doctor that specialises in the endocrine system) to determine the best treatment for them.


Related pages

On this site
Tests: ACTH, cortisol, LH, FSH, GH, hCG, free T4, TSH
Conditions: Cushing’s syndrome, endocrine syndromes, liver disease, alcoholism

Elsewhere on the web
Better Health Channel: Pituitary tumour
healthdirect Australia: Pituitary hormones
Australian Pituitary Foundation