With pituitary apoplexy, pituitary refers to a tiny gland at the base of the brain, and apoplexy refers to bleeding or loss of blood flow to an organ.
So, pituitary apoplexy is a disorder where there is either severe bleeding, or loss of blood flow to the pituitary gland, resulting in cell death and sudden loss of function.
Normally, the pituitary is a pea-sized gland, hanging by a stalk from the base of the brain.
It sits just behind the eyes near the optic chiasm, which is where the optic nerves cross.
The anterior pituitary, which is the front of the pituitary gland, contains a few different types of cells, each of which secretes a different hormone.
The largest group of cells are the somatotropes which secrete growth hormone, which goes on to promote tissue and organ growth.
The second largest cell group are the corticotrophs which secrete adrenocorticotropic hormone, or ACTH, which stimulates the adrenal glands to secrete cortisol, a hormone that controls the stress response, blood pressure, and metabolic regulation.
A smaller cell group are the lactotrophs which secrete prolactin.
Prolactin stimulates breast milk production, and also inhibits ovulation, which is when an egg cell is released from the ovary, and inhibits spermatogenesis, which is the development of sperm cells.
There are also thyrotrophs which are cells that secrete thyroid stimulating hormone, or TSH, that stimulate the thyroid gland.
And finally, there are the gonadotrophs which secrete two gonadotropic hormones - luteinizing hormone, or LH, and follicle-stimulating hormone, or FSH, both of which go on to stimulate the ovaries or testes.
The posterior pituitary, which is the back of the pituitary gland releases the antidiuretic hormone, or ADH, which is made by a part of the brain called hypothalamus.
ADH acts on the kidneys to decrease the amount of water lost in the urine.
The pituitary gland gets blood through two arteries - the superior hypophyseal artery, which forms a part of the hypophyseal portal system, a web of capillaries linking the hypothalamus to the anterior pituitary, and the inferior hypophyseal artery, which supplies the posterior pituitary.
After delivering oxygen, the blood collects in small pituitary veins and eventually drain into the nearby venous sinuses, or spaces, of the brain.
Pituitary apoplexy can develop as a result of hemorrhage or infarction. The more common way is a hemorrhage, or profuse bleeding, into the pituitary gland.
The hemorrhage is most often due to a pituitary adenoma, which is a benign tumor of the anterior pituitary gland.
Larger tumors demand more blood, and increased blood flow means increased pressure in the vessels, eventually causing them to rupture.
The blood collects in the interstitium, or the space between the cells, which makes the pituitary gland swell up.