Pituitary - A Small Gland With Big Influence
The pituitary is a small bean-shaped gland that sits at the base of the skull, below the brain and behind the nasal sinuses. It is often called the “master gland” because it controls the functions of all the other endocrine glands overseeing growth and development, sex drive and reproductive functions, thyroid function, metabolism, water balance and the stress response.
Pituitary tumors (adenomas) are relatively common and account for 15 to 20% of all brain tumors care for by neurosurgeons. Fortunately, the vast majority of these are benign slow-growing non-cancerous tumors. However, despite their benign nature they can cause serious hormonal, neurological and quality of life problems. Some adenomas secrete excess hormones, the most common of which secrete excess prolactin (prolactinoma), growth hormone (causing acromegaly) or adrenocorticotropic hormone (causing Cushing’s disease).
Prolactinomas typically cause women’s menstrual periods to stop, infertility, decreased libido and weight gain. Patients with acromegaly may develop enlargement of the hands, feet and facial bones, hypertension, diabetes, sleep apnea, colon polyps and have an increased risk of colon cancer. Patients with Cushing’s disease have progressive weight gain, hypertension, diabetes, easy bruising and psychological changes. Non-hormone secreting pituitary adenomas are typically diagnosed because they grow so large they cause headaches, visual loss, and pituitary failure. With loss of pituitary hormone production a person may experience decreased sex drive, infertility, fatigue, weight gain, low exercise capacity and low thyroid (hypothyroidism).
Pituitary tumors may be difficult to diagnose since they can produce a vast array of relatively common symptoms. However, once a pituitary problem is suspected, an MRI of the pituitary and pituitary hormonal blood levels will usually reveal the diagnosis. An MRI will show how large the tumor is and what structures (such as the optic nerves) it is compressing. Hormonal tests will typically allow a determination of the exact tumor type.
Today, most patients diagnosed with a pituitary tumor are cared for by both an endocrinologist (who specializes in hormonal disorders) and a neurosurgeon. Although patients with prolactinomas can typically be treated with a medicine (cabergoline) to lower prolactin levels and shrink the tumor, other pituitary tumor types typically require surgical removal. In the great majority of cases, a minimally invasive endonasal transsphenoidal approach provides a safe and effective route to these tumors as well as many other brain tumors that arise near the pituitary. The operation is performed entirely through a nostril using an operating microscope and an endoscope; most patients stay in the hospital for two nights after surgery.
A follow-up MRI is performed within 3 months of surgery and then at least annually to look for possible tumor re-growth. Pituitary hormonal levels are also closely monitored to determine if the pituitary has recovered or whether hormonal replacement therapy is needed. Patients are followed for many years after surgery because pituitary adenomas may recur. For individuals with invasive tumors or recurrent tumors that cannot be removed completely, radiosurgery or focused radiation therapy may be used to help prevent further growth.