Even a nonfunctioning pituitary adenoma can cause symptoms. Pressure on the optic nerve can cause blurriness or vision loss at the peripheries, classically bitemporal hemianopsia. This is considered a progressive symptom, meaning it will continue to get worse so the patient needs surgery in order to prevent further loss and hopefully improve vision. The tumor can also compress the normal pituitary tissue and cause thyroid, adrenal, and reproductive gland dysfunction. The results could be growth failure in children (growth hormone deficiency), delayed puberty or loss of sexual function or infertility or menstrual irregularities (low reproductive hormones), weakness fatigue and weight loss (low cortisol), and hypothyroidism. Patients may present with high prolactin secondary to dysinhibition. It is very rare for a pituitary tumor cause dysfunction of the posterior pituitary and few patients present with diabetes insipidus (polyuria, polydipsia, and rising serum sodium). Remember that hormone deficiencies (such as low cortisol or hypothyroidism) require immediate replacement, as these hormones are necessary for life.
Functional tumors, on the other hand, commonly secrete prolactin (→ lactation), ACTH (→ adrenal hyperplasia), or growth hormone (→acromegaly: beware of airway difficulties and obstruction).
Catherine M Burton, Edward C Nemergut Anesthetic and critical care management of patients undergoing pituitary surgery. Front Horm Res: 2006, 34;236-55