Pituitary Adenomas 

This month we are going to discuss pituitary adenomas. Pituitary adenomas are the most common tumor type in the pituitary gland. “Adenoma” refers to a benign tumor that begins in glandular tissue. Pituitary adenomas can become cancerous (called pituitary carcinomas), but these cases are extremely rare. 

Adenomas can also arise in other areas of the body besides the pituitary gland, including the colon, thyroid and the adrenal glands. 

We diagnose these tumors according to their size and the type of hormones they secrete, if any. 

Pituitary Microadenomas 

Microadenomas are tumors that measure smaller than 1 centimeter in diameter. Most pituitary adenomas are microadenomas and often do not cause symptoms. Microadenomas are usually found during an MRI to screen for another health condition. 

Pituitary Macroadenomas 

Macroadenomas are defined as glandular tumors that measure larger than 1 centimeter in diameter. Pituitary macroadenomas tend to produce more symptoms than microadenomas as they are more likely to put pressure on the brain and pituitary gland. For example, people with macroadenomas are more likely to have vision loss because of pressure on the optic nerves. 

Other vision problems that macroadenomas can cause include: 

• narrowing field of vision (bitemporal hemianopsia) 
• blurry vision 
• colors seeming less bright 
• double vision 

Large tumors can also create hormone deficiencies when the tumor puts pressure on the pituitary gland, blocking the production of certain hormones. 

Functioning Pituitary Adenomas 

Functioning pituitary adenomas are pituitary tumors that produce hormones. Functioning adenomas can be microadenomas or macroadenomas. Functioning adenomas are classified according to the type of hormone they produce. 

Cushing’s Disease (ACTH-Secreting Pituitary Adenomas) 

What Is Cushing’s Disease? 

Cushing’s disease occurs when a tumor arises in the corticotropic cells of the pituitary gland and begins to secrete a hormone called adrenocorticotropic hormone. Also called ACTH, this hormone, in turn, triggers the adrenal glands to produce the “stress hormone” known as cortisol. Cortisol affects metabolism and under normal circumstances helps the body recover from stress caused by surgery, an injury, or an infection. When the body produces too much cortisol, it leads to a range of symptoms. 

What Causes Cushing’s Disease? 

The exact cause of ACTH-secreting tumors is unknown. Women in their 30s and 40s are most commonly diagnosed with the condition, although men and women of all ages can be affected. Most ACTH-secreting tumors are benign (not cancer), though in rare cases, they can become cancerous. 

Cushing’s Disease Signs & Symptoms 

The most common symptoms of Cushing’s disease are: 

• unexplained weight gain, particularly around the neck and midsection, 
• thinning of the arms and legs and muscle weakness, 
• diabetes, 
• high blood pressure, 
• easy bruising, 
• moodiness or depression, 
• insomnia and poor concentration, 
• irregular or absent menstrual periods in women, and 
• weakening of the bones and fractures. 

Cushing’s Disease vs. Cushing’s Syndrome 

Cushing’s syndrome, also called hypercortisolism, refers to the presence of excessive amounts of cortisol in the bloodstream over a lengthy period of time. The most common cause is steroid use. Other causes include ectopic tumors and adrenal cortex tumors. Cushing’s disease refers only to hypercortisolism caused by the presence of a tumor in the pituitary gland. 

Diagnosing Cushing’s Disease 

Cushing’s disease is diagnosed using blood, urine, and saliva tests that look for abnormal amounts of the hormone cortisol. You may also need to have an MRI scan of the brain, where the pituitary gland is located, to determine the exact size and location of the tumor. Cushing’s disease is not always easy to diagnose since there are a number of other conditions that can raise the levels of cortisol in the body. Sometimes your doctor may not have a clear diagnosis even after performing the standard blood test and an MRI.  At Palmetto Endocrinology, our team will run a variety of tests to rule out other conditions. If your initial results do not confirm a Cushing’s disease diagnosis, we may use a test called petrosal venous sampling. 

Prolactinomas (Prolactin-Secreting Adenomas) 

Prolactinomas are a type of pituitary adenoma that occurs in the prolactin cells of the pituitary gland and secretes the hormone prolactin. The primary role of prolactin in the body is to stimulate a woman’s breasts to make milk during and after pregnancy. However, men and women who aren’t pregnant also produce the hormone. Prolactinomas are one of the most common types of pituitary tumors, accounting for 30 percent of all tumors found in the pituitary gland. The exact cause of prolactinomas is unknown. Men and women can develop a prolactinoma. 

Symptoms 

In women, symptoms of a prolactinoma may include lactating breasts not associated with pregnancy, and irregular or absent periods. In men, symptoms are less common, but may include discharge from the nipples, impotence, decrease in body hair, or erectile dysfunction. Most prolactinomas do not grow large enough to cause other symptoms. However, larger tumors may cause headaches or problems with vision if the tumor compresses the nearby optic nerves. 

Diagnosis 

Prolactinomas are diagnosed using blood tests that look for abnormal amounts of prolactin. You may also need to have an MRI scan of the brain, where the pituitary gland is located, to determine the exact size and location of the tumor. 

Treatment 

More than 90 percent of people who develop a prolactinoma can be treated with medication alone. Radiation therapy can be used in several ways for a prolactinoma. It may be recommended as additional therapy after surgery to prevent regrowth of the tumor. Radiation may also be used as the sole treatment if the tumor cannot be removed surgically, or if the tumor regrows after surgery. Surgery is not commonly used to treat a prolactinoma, but it is recommended in patients who develop significant side effects or who do not respond to the medication. 

TSH-Secreting Pituitary Adenomas (Thyrotropinomas) 

Thyrotropinomas are pituitary adenomas that occur in the thyrotropic cells of the pituitary gland and secrete thyroid-stimulating hormone, or TSH. TSH, in turn, triggers the thyroid gland to become overly active and produce too much thyroid hormone, a condition known as hyperthyroidism. A TSH-producing tumor is one of the rarest types of pituitary tumors. While hyperthyroidism has a number of causes, Grave’s disease being among the most common, very few cases of hyperthyroidism are linked to pituitary tumors. 

Symptoms 

The symptoms of a TSH-secreting pituitary adenoma are the same as those of hyperthyroidism. These may include: 

• rapid heart rate 
• tremors 
• unexplained weight loss 
• increased appetite 
• feeling too warm or hot 
• trouble falling asleep 
• anxiety 
• frequent bowel movements 
• a lump in the front of the neck due to an enlarged thyroid gland 

Diagnosis 

TSH-producing pituitary tumors are diagnosed using blood tests that look for abnormal amounts of TSH and thyroid hormone. You may also need to have an MRI scan of the brain, where the pituitary gland is located, to determine the exact size and location of the tumor. 

Treatment 

The primary treatment for a TSH-secreting pituitary adenoma is surgery to remove the tumor. Sometimes large tumors (macroadenomas) can be difficult to cure with surgery alone and may require therapy, such as radiation therapy.  

Nonfunctioning Pituitary Adenomas 

Nonfunctioning tumors are the most-common type of tumor in the pituitary gland. They occur most often in men between the ages of 50 and 60, but are found in men and women of all ages. The majority of nonfunctioning pituitary adenomas arise in the gonadotroph cells of the pituitary gland. In extremely rare cases, adenomas in the gonadotroph cells secrete the gonadotropic hormones luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These tumors, therefore, are classified as functioning adenomas instead of nonfunctioning adenomas. 

Symptoms  

Nonfunctioning pituitary tumors are usually not diagnosed until they have grown large enough to cause symptoms. As the tumor presses on the nearby optic nerves, symptoms may include headache and vision problems. There can be other symptoms as well if the tumor grows large enough to put pressure on the pituitary gland and block production of certain hormones. For example, men may experience loss of libido due to decreased testosterone. Women may develop irregular or absent menstrual periods. 

Diagnosis 

If your doctor suspects a nonfunctioning tumor, you may need to have an MRI scan of the brain, where the pituitary gland is located, to determine the exact size and location of the tumor. We also perform blood tests to evaluate all levels of pituitary hormones. 

Treatment 

Surgery is the most common treatment for nonfunctioning pituitary tumors. The main treatment for most pituitary tumor patients is a minimally invasive operation called transsphenoidal surgery. Sometimes large tumors (macroadenomas) can be difficult to cure with surgery alone and may require additional therapy, such as radiation therapy

Author

Joseph Mathews, MD, FACP, FACE, ECNU, CCD Joseph W. Mathews M.D., a board certified Endocrinologist and Medical Director of Palmetto Endocrinology, was born and raised in South Carolina. He earned his Bachelor of Science in Biology from the College of Charleston, Cum Laude. He then achieved his M.D. at the Medical University of South Carolina where he also completed his residency in Internal Medicine and a Fellowship in Endocrinology, Diabetes, and Metabolism. Dr. Mathews is also a Fellow of both the American College of Endocrinology and the American College of Physicians, holds an Endocrine Certification in Neck Ultrasound (ECNU) and is a Certified Clinical Densitometrist (CCD). He has extensive experience performing ultrasound guided fine needle aspiration biopsies. His practice includes a range of specializations including prescribing and fitting patients with insulin pumps. Dr. Mathews' practice has drawn patients from out of state to benefit from his expertise in thyroid disorders, diabetes, cortisol problems and their Endocrine disorders.