What causes hypopituitarism?
There are numerous causes of hypopituitarism (see Table 1). The most
common cause of hypopituitarism is a pituitary tumor (also known as a
pituitary adenoma). Pituitary adenomas are almost invariably benign (not
cancerous). However, the pituitary adenoma itself may put pressure on the
remaining normal part of the pituitary gland and limit or even destroy its
ability to produce hormones appropriately (see Figure 1).
Figure 1. Depiction of a pituitary adenoma (dark brown) next to a normal
pituitary (light brown). The normal pituitary is compressed by the tumor
which may cause hypopituitarism. (reprinted with permission, from
Kronenberg H, Melmed S, Polonsky K, Larsen PR (eds): Williams Textbook
of Endocrinology, 11th Edition, Chapter 8, Anterior Pituitary, Melmed S and
Kleinberg DL authors, Philadelphia, Penn: WB Saunders; 2008.)
Sometimes pituitary adenomas produce too much of one hormone (e.g.,
GH or PRL), which is called hyperpituitarism, while simultaneously
causing underproduction of other hormones produced in the adjacent
normal pituitary gland. In this case, reduced levels of some hormones (e.g.,
hypopituitarism due to thyroid, adrenal, and sex hormone dysfunction) can
be accompanied by overproduction of other hormones.
Hypopituitarism can also result from pituitary surgery, which might
damage part of the normal pituitary. It can result from radiation treatment
that, over time, also might damage the normal pituitary, even if the
pituitary gland was working normally when the patient was first diagnosed
with the pituitary adenoma. Therefore, a full pituitary hormone assessment
is required both before and after surgery or radiation treatment.
Other tumors that grow near the pituitary gland (e.g., craniopharyngioma,
Rathke’s cleft cyst) can cause hypopituitarism. In addition, tumors that
metastasize from cancers elsewhere in the body can spread to the pituitary
gland and can lead to hypopituitarism.
Inflammation of the pituitary can also cause hypopituitarism (see Table 1).
Sarcoidosis and histiocytosis are types of chronic inflammation that also
can result in hypopituitarism.
Radiation that focuses on a pituitary tumor or on the whole brain can result
in loss of pituitary hormone production over time. In fact, it should be
an expected consequence of radiation therapy. However, it may not occur
for months or even years after the treatment. Thus, regular monitoring of
pituitary hormone production is essential.
Pituitary apoplexy refers to a sudden hemorrhage into a pituitary adenoma
and can cause rapid onset of pituitary insufficiency. This may cause double
vision and/or visual loss, feeling quite ill, and may be an emergency
requiring immediate attention.
Severe head trauma, usually accompanied by coma or other neurologic
problems, can also cause hypopituitarism. Approximately 15% of patients
with a history of severe head trauma have been found to be GH deficient.
Other hormone deficiencies may also occur after severe head trauma.
| Table 1. Causes of Hypopituitarism |
| Cause |
Example |
| Pituitary adenomas |
Non-functioning pituitary adenoma
Functioning pituitary adenoma
Surgery on pituitary adenoma |
| Other tumors near the pituitary |
Craniopharyngioma
Rathke’s pouch cysts
Metastatic tumors |
| Radiation Treatment |
To the pituitary
To the brain |
| Inflammation |
Hypophysitis
Tuberculosis
Meningitis
Sarcoidosis
Histiocytosis |
| Hemorrhage (apoplexy) |
Sheehan’s syndrome (associated with
a hemorrhage during childbirth) |
| Severe head trauma |
|
