"Pituitary Adenomas: An Overview" (My Synopsis)

Pituitary Adenomas: An Overview
MARCY G. LAKE, DO, U.S. Naval Hospital, Sigonella, Italy LINDA S. KROOK, MD, Naval Hospital, Bremerton, Washington SAMYA V. CRUZ, MD, U.S. Naval Hospital, Rota, Spain
Am Fam Physician. 2013 Sep 1;88(5):319-327.

     Pituitary adenomas are very common and as many of 20% of the population may have one. The vast majority of these are incidentalomas with no clinical significance. Those larger than 10mm are called macroadenomas and those smaller are called microadenomas. The most common type of pituitary adenoma is a prolactinoma, followed by nonfunctioning, growth hormone secreting tumor, ACTH, FSH, LH and TSH. They arise from monoclonal tissue in the anterior pituitary (lactotroph, gonadotroph, corticotroph, thyrotroph, or somatotroph).
     PItuitary adenomas present either with hormone hypersecretion, hormone deficiency, mass effect complications (neurologic dysfunction), or incidentally. The most common hormone presentations are hyperprolactinemia, acromegaly, and cushing disease. If a hormonal origin is considered to be the cause, an endocrine panel (serum prolactin, IGF-1, LH/FSH, TSH, T4, and an appropriate cortisol test) should be ordered. An elevated serum prolactin above 250 mcg/L is most likely a prolactinoma. If it is above 500 mcg/L it would be a macroprolactinoma. Sometimes a non-prolactinoma will cause elevated prolactin when the tumor compresses the pituitary stalk, known as the "stalk effect".
     Neurologic symptoms from mass effect include headaches (stretching the neural sheath), visual changes (optic chiasm superiorly, cranial nerves III, IV, VI laterally), CSF rhinorrhea, seizures, and pituitary apoplexy. An MRI can be done with and without gadolinium, or a thinly cut, coronal plane CT can be used instead.
     Incidentally found adenomas occur by using imaging for unrelated reasons. A complete endocrine panel should be done in this case even if the patient is asymptomatic. If the tumor is functioning, it should be treated accordingly (prolactinomas are treated with a dopamine agonist and a GH or ACTH secreting tumor should be referred to neurosurgery and endocrinology). If it is a nonfunctioning macroadenoma, visual field testing should be done. Patients with visual symptoms (or with asymptomatic impingement on imaging) will need referral to an ophthalmologist. Patients with microadenomas or macroadenomas and normal vision will get a repeat MRI and endocrine panel in one year. If there is no change after one year, then testing can be repeated in 2-3 years. If the tumor becomes larger than 1 cm, then visual field testing should be repeated. Any changes in the endocrine panel need to be investigated.
     The three treatment goals for pituitary adenoma are lowering hormone secretion, shrinking the tumor, and fixing any hormone deficiencies. The dopamine agonists used in prolactinomas are bromocriptine and cabergoline. Side effect include nausea, vomiting and fatigue. When these medications are used in high doses to treat parkinsonism, there is an increased risk of heart valve problems (this has not been seen in levels used to treat prolactinomas). ACTH and GH secreting tumors are usually treated with transsphenoidal resection. Other options include octreotide and lanreotide, which inhibit GH secretion. Pegvisomant is a IGF-1 antagonist which is another option.  Treatments to shrink the tumor include radiation, radiosurgery, and resection.