Pituitary Tumor

The pituitary gland is a small, pea-sized gland located underneath the brain and behind the eyes. It is surrounded by a number of important structures, including the optic nerves, the hypothalamic region of the brain, and the internal carotid arteries. It lies in a bony area at the base of the skull (called the sella turcia, or Turkish saddle, due to its appearance). The pituitary gland has two main parts: the anterior part (called the adenohypophysis) and the posterior part (called the neurohypophysis). The adenohypophysis is thought to develop in humans by an outpouching of Rathke's pouch, which grows up from the mouth of the developing embryo. The neurohypophysis grows down from the developing brain. Each part makes different hormones. Both sections of the pituitary interact closely with the brain.

The pituitary gland's function is to secrete hormones, which in turn, control the other glands of the body. These hormones are important in growth, ovulation, breast milk production, and control of the thyroid and adrenal glands.

A number of different tumors, or cancers, can develop from the pituitary. Some tumors, called adenomas, can cause hormonal imbalances due to producing too much of a particular hormone. They can also cause hormone deficiencies when the tumor invades or compresses the normal pituitary gland tissue. Other types of tumors can cause symptoms from compression of surrounding structures, such as progressive [Page 1384]blindness from compressing the optic nerves. Headache is also a symptom in some cases.

Pituitary adenomas are tumors made up of hormone-producing cells in the pituitary. Some do still produce hormones, while others do not. If less than 1 cm in size, they are called microadenomas; the name macroadenoma is given to those larger than 1 cm. The most common type of hormone-producing adenoma is called a prolactinoma, which secretes the hormone prolactin. Symptoms of this kind of tumor include nipple discharge, missed menstrual cycles, and infertility in women and sexual problems in men. Adenomas can also secrete excess growth hormone, which produces extremely tall individuals (gigantism) if they occur before puberty, and enlargement of the limbs, facial features, and organs (acromegaly) after puberty. Rarely, pituitary tumors can also produce the other hormones. Generally, only one hormone is produced by an adenoma. Some tumors which are non-hormone–producing may be present throughout one's life and never be found.

Many adenomas can be treated by medicines which counteract the excess hormones and stop the symptoms. Prolactinomas can be treated by bromocriptine, while bromocriptine is used for growth hormone-pro-ducing adenomas.

However, if medicine does not work or if the tumor is causing symptoms due to its size, surgery is considered the best method of treatment. Generally, these tumors are removed by an incision through the nose or under the lip, which leaves minimal or no visible scarring. In certain circumstances, such as very large tumors, surgery has to be done by an incision above the forehead and through the skull.

Craniopharyngioma is a type of tumor thought to grow from remaining cells of Rathke's pouch. These tumors are seen in either adults or children, and are generally considered to be nonmalignant and slow growing. However, they can become quite large and affect nearby parts of the brain. They can cause blindness or hormone deficiencies from compressing the normal pituitary, and may also cause headaches, personality changes, memory loss, or blockage of fluid around the brain (hydrocephalus). They are made up of calcified material and cysts, which usually contain a dark, thick fluid.

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