What is a Pituitary Tumour?

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A pituitary tumour is a lesion located in the pituitary gland. The majority of pituitary tumours are pituitary adenomas (estimated at 95%) that originate from the cells of the pituitary itself. They are practically always benign and slow growing, with only a small percentage extending into neighbouring structures.

Craniopharyngiomas and meningiomas are also pituitary tumours. Other non-tumorous pituitary lesions are the vascular lesions (haemorrhages, aneurysms, etc.), inflammatory (hypophysitis), infectious (pituitary abscess, tuberculosis…), or cysts. Pituitary metastases (metastasis in pituitary of tumours of other origins) are rare.

The majority of the pituitary adenomas are usually benign and have a low level of growth. Small adenomas are generally found in the sella turcica, just behind the nose, although it is not uncommon to find these small and medium-sized tumours infiltrating the cavernous sinus. On the other hand, there are the invasive adenomas that have a more aggressive course, with a tendency to grow rapidly and invade structures like the carotid arteries and optic nerves.

Types of pituitary tumour

It can be classified:

  • Depending on the size. They are classified as micro-adenomas (when they measure 10 mm or less) or macro-adenomas (they measure more than 10 mm).
  • Depending on their capacity to produce hormones. They can be classified into functioning and non-functioning. The non-functioning adenomas do not produce hormones and, in general, the symptoms arise from the growth of the tumour and the compression of the neighbouring structures, or to the decrease in the normal production of the pituitary hormones. The functioning adenomas produce one or several pituitary hormones, and the symptoms are associated with the excessive production of the hormone, as well as also having symptoms arising from the growth of the tumour and the compression of the neighbouring structures. The functioning adenomas can be classified depending on the hormone that they produce:
    • Prolactinoma. Is the most common functioning adenoma. It is due to an increase in the secretion of prolactin. It is clinically manifested in women with a change in menstrual rhythm, galactorrhoea (spontaneous flow of milk from the breast) and a decrease in libido. In males it is associated with a decrease in sexual desire and erectile dysfunction.
    • Somatotropinoma. It is due to an excess in the production of growth hormone, and is the causing factor of acromegaly when it appears in the adult, or gigantism when it appears in infants (the growth cartilages are open). The symptoms can be progressive, which can delay the diagnosis. The most characteristic are the gradual increase in the size of the hands, feet, and the jaw, with the appearance of coarse features (need to change shoe size, the rings or hats that before fitted well do not fit anymore…), growth of lips and nose, increased sweating, tendency to snore…
    • Thyrotropinoma. They are thyrotropin (TSH) producing adenomas, giving rise clinically to hyperthyroidism due to the excessive production of thyroxin. They are very uncommon.
    • Corticotropinoma. Also known as Cushing’s disease, and it is due to an excess in the production of corticotropin, or adrenocorticotropic hormone (ACTH). Clinically, affected individuals tend to gain weight, with round or “moon face”, appearance of dark-red stretch marks, hypertension, diabetes, osteoporosis
  • According to the level of invasion of neighbouring structures. As regards the level of invasion of the cavernous sinus, the tumours are classified into four Knosp grades, with 0 being the grade in which there is no invasion of the cavernous sinus, and grade 4 in which the tumour completely surrounds the carotid.

How many people are affected by a pituitary tumour?

The pituitary adenomas are the most common intracranial tumours (estimated as 10% of all central nervous system tumours). They often go unnoticed and are detected while performing an imaging test for another reason. This is what is known as a pituitary incidentaloma.

Causes of Pituitary Tumours

They are sporadic in 95% of cases and the cause is unknown. The remaining 5% have a genetic cause, and are produced due to complex familial syndromes, such as multiple endocrine neoplasia types 1 and 4, Carney complex, or familial isolated pituitary adenomas (FIPA).

Substantiated information by:

Julia Alcazar
Joaquim Enseñat
Mireia Mora

Published: 20 February 2018
Updated: 20 February 2018

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