CLINICAL SERVICES

Pituitary Disorders

PITUITARY DISORDERS

The pituitary is a pea-sized gland located at the base of the brain. Despite its small size it is often referred to as the ‘master gland’ as it regulates the function of most other endocrine glands. The hormones it makes include:

INTERNAL MEDICINE

DIABETES

ENDOCRINOLOGY

Prolactin
Prolactin stimulates breast milk production after childbirth. It also affects sex hormone levels from ovaries in women and from testes in men.

Growth hormone (GH)
GH stimulates growth in childhood. In adults it is important for maintaining muscle mass and bone mass, and also affects body fat distribution. Through a variety of mechanisms it helps maintain health and well-being in adults.

Adrenocorticotropin (ACTH)
ACTH stimulates the production of cortisol by the adrenal glands. Cortisol, (a ‘stress hormone’) is essential for our survival. It helps to maintain blood pressure and blood glucose levels.

Thyroid-stimulating hormone (TSH)
This hormone stimulates the thyroid gland, which plays a major role in metabolism, growth and development.

Antidiuretic hormone (ADH) (also called vasopressin)
ADH regulates water balance. Too little can lead to diabetes insipidus (as distinct from diabetes mellitus which affects blood glucose).

Luteinizing hormone (LH)
LH regulates testosterone in men and estrogen in women.

Follicle-stimulating hormone (FSH)
FSH promotes sperm production in men and stimulates the ovaries to enable ovulation in women. Luteinizing hormone and follicle-stimulating hormone work together to enable normal function of the ovaries and testes.

+Pituitary Tumours

Pituitary disorders are most often caused by a pituitary tumour. These tumours are fairly common in adults but may not cause any symptoms. Fortunately the vast majority are benign, but they can interfere with the normal formation and release of hormones. These tumours are either secretory, in which case overproduction creates hormonal imbalance, or the tumour may be non-secretory, in which case problems arise because of tumour size, or because it interferes with normal function of the pituitary gland. In general problems caused by these tumours fall into three categories:

Hypersecretion
Too much of any hormone secreted into the body is usually caused by a secretory pituitary gland tumour. The most common pituitary tumour is a prolactinoma (40%). Other tumours affect the adrenal glands (causing Cushing’s syndrome), or make too much growth hormone (causing acromegaly), or rarely too much thyroid stimulating hormone.

Hyposecretion
Too little of any hormone secreted into the body is usually caused by a non-secretory pituitary gland tumour, which interferes with the ability of the normal part of the gland to create hormones.

‘Mass effects’
As a pituitary gland tumour grows and presses against surrounding structures, it may cause headaches, visual problems, or other health effects related to hyposecretion.

Injuries, certain drugs, and other conditions such as shock can also affect the pituitary gland. Loss of normal pituitary function has been reported after major head trauma.

Treatment of pituitary disorders depends of the specific underlying problem. Most pituitary tumours can be successfully treated by medication, radiation or surgery, or some combination of these therapies.

+Growth Disorders

The endocrine system plays a major role in human growth and development. Under the influence of the hypothalamus, (which secretes growth hormone-releasing hormone), the pituitary gland oversees this role. It secretes growth hormone (GH) into the blood which travels throughout the body and has multiple effects. In children, for example, GH stimulates vertical growth, or height, and is also needed for the development of muscle and bone, and the distribution of fat throughout the body. In adults, GH affects energy, bone and muscle health, and psychological well-being. Too much or too little GH can cause health problems.

Too much GH in adults causes a condition called acromegaly. This usually results from a benign tumour of the pituitary gland.

A more common growth disorder is growth hormone deficiency (GHD), associated with too little GH. Explanations for its occurrence include:

  • A child may be born with GHD
  • The condition may arise because of damage to the hypothalamus or pituitary gland as a child or adult due to tumour, trauma, infection, or radiation to the brain (usually after treatment of a tumour)
  • A deficiency in GH may also have an unidentified cause (said to be idiopathic)

Individuals with growth disorders need to be evaluated by an endocrinologist. Investigations include blood tests, scans of various kinds, and sometimes special ‘stimulation’ tests. Management of these conditions may be complex.

Treatment of growth hormone deficiency is by injectable hormone replacement. The most common cause of growth hormone excess is a benign secretory pituitary tumour. Surgical removal of the tumour is usually the treatment of choice, although medication and irradiation are other options which may be required.