What are the causes of Hypopituitarism?

There are many causes of hypopituitarism varying from tumours to trauma. The main causes are listed below.

• Intrasellar tumours
• Extralsellar tumours
• Infiltration/Inflammation
• Carotid artery aneurysm
• Trauma
• Infarction
• Haemorrhage
• Miscellaneous causes.

Each of the main causes will be considered individually.

Intrasellar tumours

Any tumour inside the pituitary is capable of causing hypopituitarism. The most common tumours to be found in the pituitary are:

• Prolactinomas - a benign tumour (adenoma) that produces excess prolactin
• Cushing's disease - an ACTH producing adenoma
• Acromegaly - a somatotrophin producing adenoma
• A non-functioning pituitary adenoma
• Metastasis - tumour cells from a cancer located somewhere else in the body.

All of these tumours can cause compression of the pituitary and therefore result in hypopituitarism.

Extrasellar tumours

Any tumour located around the pituitary is capable of causing compression of the gland and hence hypopituitarism. The main tumours that can occur in this area are:

• Optic nerve glioma - a tumour of the nerve for the eye
• Metastasis - tumour cells from cancer located somewhere else in the body
• Sphenoidal ridge meningioma - a tumour arising from the tissue surrounding the brain and spinal cord
• Craniopharyngioma - a tumour arising from the remnants of Rathke's pouch
• Pinealoma - a tumour of the pineal gland.

Infiltration/Inflammation

Any condition that can cause a disruption to normal pituitary function can cause hypopituitarism. There are a number of infiltrative/inflammatory conditions that can result in dysfunction such as:

• Tuberculosis
• Sarcoidosis
• Menigitis
• Haemochromatosis
• Amyloidosis
• Granulomas of Hand-Schuller-Christian disease
• Idiopathic hypophysitis

Carotid Artery Aneurysm

An expansion of the carotid artery can press on the pituitary and cause hypopituitarism.

Trauma

Severe head trauma can cause either temporary or permanent damage to the pituitary gland. The damage to the gland can produce hypopituitarism.

Infarction or Haemorrhage

Sheehan's syndrome - during pregnancy, the blood flow through the pituitary gland increases. This syndrome results from the vasoconstriction after a post-partum haemorrhage. This decrease in blood flow to the pituitary results in infarction and either acute or chronic symptoms of hypopituitarism.

Pituitary apoplexy - this is a dramatic condition in which a pre-existing adenoma undergoes infarction usually involving some haemorrhage. The patient may present with a sudden collapse and will later show either single or multiple hormone deficiencies.

Miscellaneous causes

Idiopathic hypopituitarism - this is a relatively common cause of hypopituitarism. The cause of the condition is not fully understood, but is thought to either be as a result of an immunological process or a primary hypothalamic disease.

Irradiation - radiation therapy to any intracranial lesion can result in hypopituitarism. It is not fully understood if the damage is to the hypothalamus or pituitary.

The empty sella syndrome - this is a condition in which the pituitary fossa (sella turcica) is occupied by an extension of the subarachnoid space. An empty sella can occur for two main reasons. The first reason is due to an anatomical variant, whereas the second is due to the surgery, radiotherapy or infarction of a pituitary tumour.