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Acromegaly

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Acromegaly is a disease of growth hormone (GH) hypersecretion. Usually, the source is the pituitary tumor. These are always benign (non-cancerous) but often large and invasive. GH itself does not promote growth. Instead, it induces production of yet another hormone, IGF-I or somatomedin C (SmC) in virtually all organs and tissues. High IGF-I in turn promotes somatic growth. Clinically, acromegaly is associated with increased amount of soft tissues (large puffy hands, rough facial features), bone overgrowth (protruding lower jaw, frontal bossing) tall stature (if the disease began before puberty). Other symptoms include headache, sweating, snoring, sleep apnea, carpal tunnel syndrome and joint aches.

The development of the disease is insidious, and at the time of diagnosis the patient usually recalls the existence of symptoms for 5-10 years. Even family rarely notices the gradual development of the disease. Often, the diagnosis is made by a stranger or by a new physician during his/her first meeting with the patient.

Acromegaly is a potentially life-threatening disease: Life expectancy in the patients is shortened on the average by
10-15 years. Heart disease, diabetes and sleep apnea all contribute to excess mortality. It is also possible that certain cancers (colon, breast, and prostate) may be more frequent.

The biochemical diagnosis rests on the finding of high GH and IGF-I levels. Often, the reliance on GH confuses the picture: most laboratories state that GH below 10 or 15 ng/ml is normal. Physicians who are not experienced in pituitary diseases often tell the patient that the diagnosis of acromegaly is excluded if plasma GH is “normal.” In fact, active acromegaly may be accompanied by perfectly normal GH levels, often as low as 0.5-1 ng/ml. Over the past 5 years we have seen close to 20 such patients, whose diagnosis was missed elsewhere because of “normal” GH. We often put such patients in the Clinical Research Center to perform frequent blood sampling and do certain dynamic tests to establish the diagnosis with certainty. Currently, plasma IGF-I is the only valid measure of biochemical activity of the disease. If it is elevated, the diagnosis of acromegaly should be suspected. Similarly, only normalization of IGF-I can serve as a valid parameter of cure.

Surgery is the first option for the patients. It should be done by an experienced pituitary surgeon. A minimum of 20 pituitary surgeries per year is a criterion suggested by some to indicate sufficient experience and proficiency. In experienced hands, microadenomas are totally removed in 80-90% of cases, while the success rate in macroadenomas depends on the size and the invasiveness of the tumor. The success rate of less experienced surgeons is about ½-1/3 as low as that and the incidence of complications is 3-4 times as high. Very large and invasive tumors often cannot be removed surgically, but a sufficient debulking is important to improve the efficacy of subsequent treatments.

Pituitary Disorders
  Prolactinoma
  Acromegaly
  Cushing's Disease

Symptoms

Swelling of the hands and feet

Facial features become coarse as bones grow

Body hair becomes coarse as the skin thickens and/or darkens

Increased perspiration accompanied with body odor

Protruding jaw

Voice deepening

Enlarged lip, nose, and tongue

Thickened ribs (creating a barrel chest)

Joint pain

Degenerative arthritis

enlarged heart

Enlargement of other organs

Strange sensations and weakness in arms and legs

Snoring

Fatigue and weakness
headaches

Loss of vision

Irregular menstrual cycles in women

Breast milk production in women

Impotence in men

After transsphenoidal surgery the patient stays in the hospital overnight. Only rarely do we have to prolong hospitalization for another 2-3 days. Patients usually return to light work within a couple of weeks, but strenuous exertion is not recommended for a month. The recurrence rate is below 10%.

Radiation is very effective in preventing tumor regrowth, but its ability to normalize hormone levels is limited and takes years. Stereotactic radiosurgery (gamma knife) is a confusing misnomer as no surgery is involved. While it is becoming more popular, there is still no evidence that it is any more effective than conventional radiation in normalizing hormone levels. Also, it has a higher complication rate.

Medical Therapy

Medical therapy is most often used if surgery does not result in a cure and sometimes to shrink large tumors before surgery. Three medication groups are used to treat acromegaly.

Somatostatin analogs (SSAs) are the first medication group used to treat acromegaly. They shut off GH production and are effective in lowering GH and IGF-I levels in 50 to 70 percent of patients. SSAs also reduce tumor size in around 0 to 50 percent of patients but only to a modest degree. Several studies have shown that SSAs are safe and effective for long-term treatment and in treating patients with acromegaly caused by nonpituitary tumors. Long-acting SSAs are given by intramuscular injection once a month.

Digestive problems-such as loose stools, nausea, and gas-are a side effect in about half of people taking SSAs. However, the effects are usually temporary and rarely severe. About 10 to 20 percent of patients develop gallstones, but the gallstones do not usually cause symptoms. In rare cases, treatment can result in elevated blood glucose levels. More commonly, SSAs reduce the need for insulin and improve blood glucose control in some people with acromegaly who already have diabetes.

The second medication group is the GH receptor antagonists (GHRAs), which interfere with the action of GH. They normalize IGF-I levels in more than 90 percent of patients. They do not, however, lower GH levels. Given once a day through injection, GHRAs are usually well-tolerated by patients. The long-term effects of these drugs on tumor growth are still under study. Side effects can include headaches, fatigue, and abnormal liver function.

Dopamine agonists make up the third medication group. These drugs are not as effective as the other medications at lowering GH or IGF-I levels, and they normalize IGF-I levels in only a minority of patients. Dopamine agonists are sometimes effective in patients who have mild degrees of excess GH and have both acromegaly and hyperprolactinemia—too much of the hormone prolactin. Dopamine agonists can be used in combination with SSAs. Side effects can include nausea, headache, and lightheadedness

Agonist: A drug that binds to a receptor of a cell and triggers a response by the cell, mimicking the action of a naturally occurring substance.

Antagonist: A chemical that acts within the body to reduce the physiological activity of another chemical substance or hormone.



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