Pituitary Tumors

The pituitary gland is located in the sella turcica in the body of the sphenoid bone. The tuberculum sellae forms the anterior border of the sella turcica, and the dorsum sella demarcates the posterior border. The cavernous sinus is found in the lateral sellar compartment and borders each side of the pituitary. The optic apparatus lies above the sella.

The pituitary gland is formed by two distinct lobes: anterior (adenohypophysis) and posterior (neurohypophysis). The anterior lobe contains glandular epithelial cells, which secrete endocrine hormones such as adrenocorticotropic hormone (ACTH), thyrotropin-stimulating hormone (TSH), prolactin, growth hormone (GH), luteinizing hormone (LH), and follicle-stimulating hormone (FSH). The posterior lobe represents the termination of the hypothalamohypophysial tract and stores oxytocin and vasopressin. In general, pituitary adenomas represent benign neoplasms of the anterior lobe.

Pituitary tumors are classified according to size, with microadenomas referring to adenomas 10 mm or smaller and macroadenomas to adenomas larger than 10 mm. The tumors can also be categorized according to function with nonfunctioning adenomas, including gonadotroph adenomas, null cell adenomas, and oncocytomas. Hyperfunctioning tumors secrete growth hormone, prolactin, ACTH, and TSH.

Craniopharyngiomas are solid or mixed solid-cystic tumors which arise from the remnants of Rathke’s pouch. They are relatively rare and have a bimodal age distribution, with the first peak occurring in children between 5 and 14 years of age, and the second peak developing in adults between 50 and 75 years of age. Males and females appear to be equally affected. Although these tumors are considered benign by histology, they frequently shorten life. Malignant transformation is a rare occurrence.

Clinical Manifestations. In general, the nonfunctioning adenomas cause clinical symptoms by exerting mass effects on neighboring structures. The most common symptom is progressive visual impairment secondary to compression of the optic chiasm from suprasellar growth of the adenoma. Patients may complain of diminished vision in the temporal fields (bitemporal hemianopsia) or decreased visual acuity. Other symptoms caused by a sellar lesion include headaches and diplopia from oculomotor compression. Patients may also present with hyposecretion of hormones resulting from compression of different pituitary cell types by the adenoma. Impaired secretion of LH is the most common deficiency, with females reporting amenorrhea and males complaining of decreased libido.

Only gold members can continue reading. Log In or Register to continue