Dr Emma Duncan, Staff Specialist in Endocrinology,
Princess Alexandra Hospital
The Pituitary Gland
What Can Go Wrong?
Why Tumours Cause Problems
Excess Hormone Production By Pituitary Tumours
Prolactinoma
Acromegaly
Cushings Syndrome
Thyroid Stimulating Hormone Tumours
Non Functioning Tumours
Are Pituitary Tumours Hereditary?
Hormone Deficiency Conditions
Pituitary Deficiency
Replacement Of Pituitary Hormones.
ACTH Deficiency
Follicle Stimulating Hormone And Leutinising Hormone Deficiency
Thyroid Stimulating Hormone Deficiency
Growth Hormone Deficiency
Diabetes Insipidus
Other Pituitary Problems:
Craniopharyngioma
Rathke’s Cleft Cyst
Sheehan’s Syndrome
Lifelong Follow-Up
The Pituitary Gland
The pituitary gland is a small gland about the size of a pea, situated in a bony hollow at the base of the brain, about 5 cm behind the bridge of the nose. It is one of the most important endocrine glands, because it controls hormone secretion from a number of other glands, such as the adrenal gland and thyroid gland.
What Can Go Wrong?
Pituitary problems can occur in both men and women, at any age. The most common problem is a small growth within the gland, called a tumour. Tumours in the pituitary gland are very common - between 10-25% of the population have tumours in the pituitary gland. Most often, these cause no problems at all. However, each year around 10-20 people per million in the population will have tumours in their pituitary gland that do cause problems and need help. In Australia, this means around 200-400 people a year will have a pituitary tumour that needs attention. Problems can arise from both large and small tumours. Small tumours (less than 1 cm) are called microadenomas. Larger tumours (greater than 1 cm) are called macroadenomas. Pituitary tumours are almost never cancerous.
Occasionally, pituitary problems can arise because of unusual development before birth. This can result in a craniopharyngioma or Rathke’s cleft cyst. Pituitary problems may also occur after damage to the gland at any time in life. This might occur after radiation of the head, major head trauma, surgery involving the pituitary area, or other insults to the pituitary gland. Other forms of brain tumour can occur in the area of the pituitary gland also.
Pituitary problems may be suspected by a doctor after taking a history and examining a patient. To make a firm diagnosis, the doctor may do a scan of the pituitary gland (either an MRI scan or a CT scan) and organize blood tests to look at the hormones normally secreted by the gland. Vision will be looked at very carefully, as many of the nerves involved in vision and eye movement are close to the pituitary gland.
Endocrinologists are medical specialists who deal with hormone problems, and therefore can help to sort out pituitary problems.
Pituitary tumours can cause problems for several reasons. The tumour may secrete an excess amount of hormones, outside the usual control of the gland. Tumours may also be nonfunctioning, and not secrete anything. Tumours can press on the normal gland and prevent the normal secretion from the pituitary gland. Large tumours may cause problems with other structures in the same region as the pituitary gland. These include the optic chiasm (where the optic nerves from the back of the eye cross over on their way to the brain). Other nerves in the area include the nerves that control eye movement. Occasionally, patients with pituitary tumours may bleed into their pituitary tumour, which can result in sudden headache, visual problems and hormone problems.
If a patient has a pituitary tumour, they may need medication, surgery and/or radiotherapy. This will depend upon several factors, including the size of the tumour, whether it is secreting a hormone in excess and whether it is causing damage to any other structures in the area, as well as the general health of the person affected. If the tumour has resulted in a lack of normal hormone secretion by the normal gland, then these hormones will need replacing. Normal secretion by the pituitary gland may also be affected as a consequence of treatment (either by surgery or by radiotherapy) and hormone replacement may be needed in this circumstance also.
As mentioned above, some tumours make an excess production of hormones. Usually, only one excess hormone is secreted by pituitary tumours. However, many tumours do not appear to secrete any hormone in excess. These are called “non-functioning” tumours.
The commonest type of pituitary tumour that secretes excessive hormone is a prolactinoma. Normally, the pituitary gland secretes prolactin to help in the production of breast milk and lactation. If too much prolactin is secreted by a pituitary tumour, the breasts may swell (this is called gynaecomastia) and may even make milk (this is called galactorrhea). This can occur in people who are not breastfeeding (including in men). Women with prolactinomas often notice their menstrual periods stopping. Men may notice that they have lost their libido (interest in sex) and may have impotence.
Prolactinomas are usually managed by medications that both prevent the excess secretion and can even shrink the tumour. In some cases, patients with prolactinomas may need surgery. Autopsy studies have suggested that around 10% of the population have tiny microprolactinomas in their pituitary gland; these are usually silent and do not cause any clinical problems. However, around 10 in a million people will have clinical problems due to a prolactinoma each year (so around 200 people affected each year in Australia).
Excess secretion of growth hormone causes a condition called acromegaly. This results in growth of those tissues able to grow. If there is excess growth hormone in children before their long bones fuse (usually in their mid to late teen years), they grow excessively tall – this is called gigantism. However, in adults whose bones have fused, excess growth hormone secretion can result in enlargement of the jaw, forehead, hands and feet. Bony overgrowth at joints can cause a particular type of arthritis. Patients may also have enlarged soft tissues, such as a big tongue, big nose, and very fleshy hands. The swollen tissues can cause patients to snore. Typically, patients have thick, greasy and sweaty skin and may have a lot of skin tags. Some patients have high blood pressure and even diabetes as a consequence of too much growth hormone.
Patients with acromegaly have traditionally required surgery to remover the tumour and often radiotherapy also to control their excess secretion. However, there are now medicines that may control the excess growth hormone secretion. For many people now, medicines may be the best first option. In others, the medicines may be necessary after an operation if there is still excess growth hormone.
Management has to be decided on a case by case basis. Acromegaly is not common – around 4 per million in the population per year, so around 80 people will be affected in Australia each year.
Adrenocorticotrophic hormone (ACTH) is the hormone that controls secretion from the outer part (or cortex) of the adrenal gland. The most important hormone made by the adrenal cortex is cortisol. Excess cortisol causes a condition called Cushing’s syndrome, and when this is due to excess ACTH from the pituitary gland this is called Cushing’s disease. Cushing’s syndrome results in excessive fat on the torso; muscle wasting and weakness in the limbs (patients may find it difficult to climb stairs or to get out of a chair or up from squatting position); thin bones (osteoporosis); thin skin that easily bruises; a reddened rounded face (sometimes called a moon face); facial hair (hirsutism) and thinning of head hair; menstrual changes, infertility, and loss of libido; hypertension; acne; high blood sugars; and mood disturbance including depression, euphoria, fatigue and difficulty sleeping. Although Cushing’s syndrome is quite common in patients taking excess doses of steroid hormones for other health reasons (such as bad asthma or bad rheumatoid arthritis), Cushing’s disease is rare, with around 2 people per million in the population affected each year, so around 40 people affected in Australia annually.
Medication is sometimes used temporarily to get patients ready for theatre. Surgery is the usual means of managing Cushing’s Disease, although patients may often need further management over time such as radiotherapy or even a second operation.
Pituitary tumours secreting excess thyroid stimulating hormone (TSH) are even more rare than the above tumours. If this type of tumour is present, it causes an overactive thyroid (please note that the vast majority of patients with an overactive thyroid do not have pituitary tumours secreting TSH!).
Under the microscope, pituitary tumours often look as if they are secreting excess follicle stimulating hormone (FSH) and luteinising hormone (LH) but do not actually cause any symptoms or signs related to excess of these hormones. Therefore these tumours are often categorized as non-functioning tumours. Also, some pituitary tumours genuinely do not have any hormone secretion evident and the term non-functioning tumour is used for these also.
Sometimes pituitary tumours can run in families. This can occur as part of the Multiple Endocrine Neoplasia syndrome type 1, associated with excess parathyroid hormone production and with tumours in the pancreas.
Any cause of damage to the pituitary gland can result in a loss of its normal hormone production. This can occur because of tumour pressing on the normal gland, bleeding into the gland, radiotherapy, surgery, or any other cause of damage. The gland may lose all its normal production of hormones (called panhypopituitarism); alternatively, only some of the normal hormone production may be lost (partial hypopituitarism). Occasionally, if a pituitary tumour has been pressing on the normal gland, recovery of normal pituitary function can occur after surgery.
As described above, the pituitary gland controls the secretion of a number of hormones from other glands. If a person is deficient in their pituitary hormone production, it is most common to replace the target gland hormone production rather than the pituitary hormone.
Persons deficient in ACTH will not make sufficient cortisol from their adrenal glands. These people will need to take adequate cortisol replacement in the form of hydrocortisone, cortisone acetate, prednisolone or other corticosteroid hormone. In times of sickness, the dose of the replacement hormone will need increasing. Patients on corticosteroid hormone replacement need to carry a card in their wallet or wear a medic-alert bracelet or similar in case of an accident or emergency, when it will be essential for the caring emergency team to know that the patient will need corticosteroids.
FSH and LH are important in women for normal menstrual cycling, which includes production of estrogen and progestogen by the ovary, the regular release of eggs from the ovaries, and normal menstruation. In men, LH and FSH control testosterone and sperm production from the testes (or testicles). Deficiency of FSH and LH will result in lack of normal menstrual cycling and infertility in women, and in impotence and infertility in men. Young women (less than 50) with FSH and LH deficiency are usually given replacement estrogen and progestogen, either in the form of HRT or the oral contraceptive pill; this is particularly important to prevent osteoporosis. Replacement of these hormones in women of postmenopausal age (over 50 years) is no longer routine. Men with LH and FSH deficiency are usually treated with testosterone, which can be given in several different ways including injection, implantation, and a gel form.
Patients with LH and FSH deficiency will need special help for fertility.
Patients deficient in TSH are given thyroxine (a tablet) which is the main hormone secreted by the thyroid gland.
Children with GH deficiency will not grow properly and replacement of GH is important to prevent them from being too short. Adults with GH deficiency have perturbations in their fat and muscle balance, such that they tend to have increased body fat and reduced muscle mass. They may also have mood disturbance. Replacement of GH in adults is controversial and is not currently available on the Pharmaceutical Benefits Scheme in Australia.
The posterior pituitary gland normally secretes a hormone called anti-diuretic hormone (also known as vasopressin) which causes the kidney to hold onto water. Lack of this hormone causes excess loss of water by the kidneys. This is known as diabetes insipidus. Patients may pass great quantities of urine and feel terribly thirsty. This hormone can be replaced both by tablets and by nasal spray.
A craniopharyngioma is a cyst-like tumour which occurs in the area of the pituitary gland. It is thought that these tumours arise because of the way the brain forms during early life. Craniopharyngiomas often cause loss of normal hormone production by the pituitary gland as well as compression on other structures in the area. Craniopharyngiomas are rare tumours, with around 1-2 per million in the population diagnosed each year. Craniopharyngiomas are sometimes diagnosed in childhood but may not become evident until adulthood. Surgery is usually required, as is radiotherapy. It is not uncommon for the tumour to reoccur.
Rathke’s cleft cyst is a similar lesion to a craniopharyngioma but has a better outlook as it does not usually recur after removal by surgery. Occasionally such cysts may simply be drained rather than a more extensive operation taking place; this procedure may be repeated if necessary.
Sheehan’s Syndrome refers to damage to the pituitary gland due to major blood loss (infarction of the pituitary gland), usually during delivery of a baby. It is often first diagnosed when the mother is unable to breast feed her baby because of loss of prolactin production by the pituitary gland. With modern obstetric care, it is unusual for women to have massive bleeds around the time of giving birth, and this syndrome therefore has become less common.
There are other conditions that affect the pituitary gland but these are even more rare than the conditions listed above.
As pituitary problems may be quite complex and may evolve with time, lifelong follow-up by specialist endocrinologists is advisable, even after successful correction of the initial problem.
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This article updated: July 2006