What is Acromegaly?

Growth hormone (GH) is essential for the normal physical growth of the human body in childhood. GH progressively increases during childhood and peaks during puberty. Produced by the anterior pituitary gland, the hormone has many functions within the body. GH is responsible for strengthening and increasing mineralization of the bones, increasing protein synthesis, stimulating the immune system, decreasing liver uptake of glucose, stimulating the growth of all organs except for the brain, and increasing muscle mass. Growth hormone deficiencies can lead to growth failure, short stature, and delayed sexual maturity in children, and weaker bones in adults.

Often, the first noticeable sign of acromegaly is changes in the size of the hands and feet. Someone may notice that she needs a bigger ring size or that her feet are growing, especially in width. Acromegaly can also cause changes to the face, such as an enlarged nose, protruding brow and lower jaw, wider spacing between the teeth, and thicker lips. Other signs of the condition include headaches, excessive sweating and body odor, muscle weakness, fatigue, an enlarged tongue, loss of interest in sex, enlarged organs including the heart, achy joints, lack of joint mobility, vision impairment, skin tags, coarse, thickened, and oily skin, erectile dysfunction in men, and menstrual irregularities in women. Snoring may occur due to upper airway obstruction, and enlargement of the vocal cords and sinuses may cause a deeper, huskier voice.

As acromegaly progresses, it leads to serious health issues. High blood pressure (hypertension), goiter, osteoarthritis, carpal tunnel syndrome, diabetes mellitus, vision impairment, sleep apnea, and spinal cord compression can occur. Polyps -- precancerous growths -- may also form on the lining of the colon, and heart disease is possible. Early treatment of the condition can prevent complications or keep them from becoming worse. Premature death can occur in individuals with untreated acromegaly.

A pituitary adenoma, a benign tumor that produces too much growth hormone, is the cause of acromegaly in more than 95% of cases. Most growth hormone-secreting pituitary tumors are more than one centimeter in size. How quickly the adenoma grows, and how much excess GH it produces, varies from person to person. In general, younger individuals tend to have more aggressive adenomas. Most pituitary adenomas occur spontaneously (in other words, they are not genetic).

In a small percentage of cases, acromegaly is caused by a tumor in another part of the body, such as elsewhere in the brain, the lungs, or the pancreas. Sometimes these tumors produce growth hormone themselves. Other times, they produce growth hormone-releasing hormone or GH-RH, which stimulates the pituitary gland to make more growth hormone.

Approximately 17% of the American population have adenomas. However, adenomas rarely cause symptoms or create excess growth hormone. Experts estimate that three to four individuals out of one million people develop acromegaly every year. Approximately 60 people out of every one million have the disease at any given time. These numbers may not accurately reflect the true prevalence of the condition because medical practitioners often overlook and misdiagnose it.

After taking a medical and family history and doing a physical examination, if a physician suspects acromegaly, he may order one or more tests to confirm the diagnosis:

• GH and IGF-I Measurement: This is a fasting blood test that measures growth hormone and IGF-I levels. If the test shows high hormone levels, the doctor may suspect acromegaly.
• Growth Hormone Suppression Test: The doctor will measure hormone levels before and after the patient consumes a glucose solution. Glucose suppresses growth hormone levels in healthy individuals. A person with acromegaly will often have high GH levels after drinking glucose.
• MRI: Once the doctor has determined his patient has acromegaly, he may order a magnetic resonance imaging (MRI) scan to look for a pituitary tumor. If no pituitary tumor is present, imaging of the chest, pelvis, and abdomen can help locate a nonpituitary tumor.

Surgery to remove a pituitary adenoma is the first line of treatment for acromegaly. During a transsphenoidal surgery, a neurosurgeon accesses the pituitary gland and removes the tumor through the nose or the upper lip. If the surgery is successful, growth hormone levels drop dramatically. Within a few days of a successful surgery, soft tissue swelling and facial appearance improve. The success of the surgery depends on a surgeon's experience and skill level, as well as the size of the tumor. The most successful surgeries involve tumors smaller than one centimeter in diameter. Overall remission rates after surgery range from 55-80 percent.

Medications can help lower GH levels, in lieu of or following surgery.

• Somatostatin Analogues are a synthetic form of the brain hormone somatostatin. They can interfere with the pituitary's production of growth hormone.
• Dopamine Agonists lower the levels of GH and IGF-I in some people. They can also decrease the size of pituitary tumors.
• Growth Hormone Antagonists block the effect of growth hormone on the body's tissues. This medication can lower IGF-I levels and decrease symptoms of acromegaly, but it does not decrease growth hormone levels or reduce pituitary tumor size.

A patient may require radiation therapy if tumor cells are still present following surgery. Radiation therapy kills tumor cells and slowly normalizes growth hormone levels in the body.

• Conventional Radiation Therapy is typically given every weekday for four to six weeks, but the effects may not be noticeable for many years.
• Proton Beam Therapy delivers a high dose of radiation directly to the tumor.
• Stereotactic Radiosurgery delivers a single dose of high radiation to the tumor. Growth hormone levels in the body may return to normal within five years with this type of radiation.