Pituitary Tumor

Pituitary tumors arise from the pituitary gland within the base of the skull. These tumors are almost always benign. Symptoms arise when these tumors secrete hormones or become large enough to compress adjacent structures. Rarely, these tumors may spontaneously hemorrhage.
As these tumors enlarge, the normal pituitary function is destroyed. This destruction produces various hormonal deficiencies since the pituitary controls the action of other endocrine glands within the body. Pressure on nearby structures can produce double vision and facial numbness. The nerves of vision, the optic nerves, are directly above the pituitary gland and upward growth of pituitary tumors frequently causes progressive visual loss. This visual loss typically begins from each side of the field of vision leading to tunnel vision and then blindness.
The pituitary gland is the "master gland" of the body. The pituitary lies embedded within the skull base in a small cavity called the sellar tursica. The gland is connected to the overlying brain by the pituitary stalk. The brain controls the synthesis, or storage and release, of many hormones from the pituitary gland by secreting hormones through the pituitary stalk to the pituitary gland. These hormones stimulate (or inhibit) the production of trophic hormones by the pituitary. Trophic hormones travel through the blood to the other glands in the body, controlling their functions. For example, corticotrophin releasing hormone (CRH) is produced in the brain and travels from the hypothalamus to the pituitary through the pituitary stalk. CRH causes the pituitary to produce and release thyroid stimulating hormone (TSH). TSH travels through the blood to the thyroid gland in the neck. Here TSH stimulates the production of thyroid hormone which effects the metabolic rate of all tissues of the body. Growth hormone is also released by the anterior pituitary gland and affects growth and maintenance of various tissues directly, without an intermediary gland. And, in a final example, vasopressin is stored but not produced by the posterior pituitary. Its release by the posterior portion of the gland promotes the reabsorption of water by the kidneys.
Pituitary tumors make themselves known by the overproduction of certain hormones either by destroying normal pituitary function and causing a lack of hormones, or by enlarging and compressing adjacent structures causing neurological problems. Generally, these tumors can be subdivided in to non-hormone producing tumors of the pituitary gland, hormone producing tumors of the pituitary gland, other intra-sellar tumors, and para-sellar tumors.  Para-sellar tumors which occur in the vicinity of the sellar tursica can mimic the symptoms of pituitary tumors.
Nonhormone-producing Tumors: Tumors arising from the pituitary which secrete no hormones are deemed null cell tumors. These tumors are quite common.  In fact, null cell tumors measuring a few millimeters in size may be found in up to one-quarter of autopsied pituitary glands. They may grow slowly, destroying normal pituitary function (hypopituitarism) or may compress nearby structures causing neurological problems.