Pituitary Disorders

Classification of Pituitary Adenomas

Adenoma is a medical term used for tumor.

Pituitary adenomas may or may not secrete hormones. The majority of tumors do secrete hormones and can be classified by which hormone(s) they are producing.

The most common type of pituitary tumor is the prolactin-secreting prolactinoma. These account for nearly 30% of all pituitary tumors. Lactation is the primary symptom of this tumor. Lactation can occur in other types of tumors as well.

Null Cell
The second most prevalent type, comprising approximately 25% of pituitary tumors, is called a null cell adenoma. Null cell adenomas are considered non-functioning because they do not produce any hormone. They are sometimes referred to as non-secreting tumors. Lactation can be a symptom that occurs with this tumor type even though it is not a prolactinoma.

Growth hormone-secreting tumors, seen in about 10-15% of patients, are associated with acromegaly, a clinical syndrome that involves a thickening of the bones of the hands, feet, cheeks, and jaw.

Another 10-15% of pituitary adenomas are accounted for by ACTH-secreting tumors, which are often the cause of Cushing’s disease.

Some pituitary tumors are also capable of secreting more than one hormone. The most common multi-hormonal tumor secretes both growth hormone and prolactin.

Tumors that secrete TSH or FSH and LH are not frequently seen.