GIGANTISM & ACROMEGALY

Acromegaly, also called as gigantism, is a rare disease in which you make too much growth hormone. Due to this there are various symptoms which slowly develop over several years. Common symptoms are that your hands and feet become larger, and features of your face may become more prominent. The cause is usually a small non-cancerous tumor in the pituitary gland. The pituitary gland lies just below the brain. Pituitary hormone produces several hormones, including growth hormone. (A hormone is a chemical that is made in one part of the body, passes into the bloodstream, and then can have effects on other parts of the body.)

Hormone secreted by the body is partly controlled by other hormones which come from a small part of the brain called the hypothalamus. This is just above the pituitary.


It makes growth hormone-releasing hormone (GHRH) which stimulates the pituitary to make growth hormone when the blood level of growth hormone is low. It also makes a hormone called somatostatin which prevents the pituitary from making growth hormone when the level of growth hormone is high.

Growth hormone helps to stimulate growth and repair of various body tissues. It is needed in childhood to help children to grow. Growth hormone acts on some tissues directly.

Causes

The cause of acromegaly is pituitary gland overproducing growth hormone (GH) over time. Secretion of GH into your bloodstream triggers your liver to produce a hormone called insulin-like growth factor-I (IGF-I). Excess of IGF-I can cause abnormal growth of your soft tissues and skeleton and other signs and symptoms characteristic of acromegaly and gigantism.

A tumor is the most common cause of too much GH production in adults:

  • Tumors of Pituitary. Majority of acromegaly cases are caused by a noncancerous (benign) tumor (adenoma) of the pituitary gland. The tumor secretes excessive amounts of growth hormone, causing many of the signs and symptoms of acromegaly. Some of the symptoms of acromegaly, such as headaches and impaired vision, are due to the tumor mass pressing on nearby brain tissues.
  • Tumors from other sites. Tumors in other parts of the body, such as the lungs, pancreas or adrenal glands, cause the disorder in a few people with acromegaly. Sometimes, these tumors actually secrete GH. In other cases, the tumors produce a hormone called growth hormone-releasing hormone (GH-RH), which stimulates the pituitary to make more GH.

Symptoms

The literal meaning of acromegaly is ‘enlarged extremities’ or ‘enlarged hands and feet’. This is a typical feature, but there are many other symptoms. The symptoms develop gradually. Some people have symptoms which develop over 10-15 years before the diagnosis is made.The symptoms are divided into two types: those caused by too much growth hormone, and those caused by the enlarging tumor (adenoma) in the pituitary.

Symptoms caused by too much growth hormone

GH excess in your bloodstream can affect various tissues in your body which can make them thicken or grow. Most patients develop following symptoms:

  • Large and broad hands and feet. Your glove and shoe size may increase over the years. You may not be able to get a wedding ring off.
  • Your skin may thicken (particularly on the face) and become more greasy and sweaty.
  • Face changes may include: thickened lips and nose, thickening of your scalp, your jaw becoming more prominent. These changes develop very gradually so may not actually be noticed by your family or friends. However, looking back at old photographs may suggest your facial appearance has changed.
  • Thickening of vocal cords which may cause your voice to deepen.
  • Your tongue may enlarge so you may often bite your tongue.
  • Thickening of cartilage may cause arthritis in various joints.
  • Nasal passage thickening can make you snore loudly and may cause obstruction in airflow when you are asleep (sleep apnoea). This can make you have a poor night’s sleep with daytime drowsiness.
  • Carpal tunnel syndrome. This is where a nerve going through the wrist is squashed by thickened tissue. It can cause pain, tingling and weakness in parts of the hands or arms.
  • Irregular or absent periods (in women) may occur.

Other symptoms may include:

  • Tiredness in general.
  • Muscle weakness.
  • About 1 in 5 people with acromegaly also develop diabetes as growth hormone counters the effects of insulin.
  • Raised blood pressure develops in about 1 in 3 cases.
  • Raised risk of heart disease and stroke. This is probably because of the increased risk of developing high blood pressure and diabetes.
  • increased chance of developing polyps (small benign growths) in the bowel and a slightly increased chance of developing bowel cancer. People with acromegaly are now routinely screened for these conditions.
Symptoms caused by the growing tumor

Tumor, in many cases, remains small and does not cause pressure symptoms. However, in some cases the tumor grows enough to cause pressure on the nearby tissues. This can lead to:

  • Headaches.
  • Vision problems. The tumor may press on the optic nerves (the nerves going from the eyes to the brain) which are just next to the pituitary.
  • Other normal cells in the pituitary may become squashed and damaged. Therefore, you may develop a lack of other hormones that are made by the pituitary. This can cause an underactive thyroid gland and/or an underactive adrenal gland which can cause various other symptoms.

Diagnosis

  • Blood test can measure the level of growth hormone. However, a single test is not reliable. This is because the levels of growth hormone in the body fluctuate a lot throughout the day in all people.
  • Acromegaly diagnosis can also be made by a glucose tolerance test. In this test you drink a sugar drink containing 75 grams of glucose. You then have a series of blood tests over two hours. The glucose should lower the blood level of growth hormone. However, if you have acromegaly the growth hormone level remains high.
  • Blood test may measure the level of IGF-1 if acromegaly is suspected. This may also be used as an index of disease activity to assess how well treatment is working.
  • Magnetic resonance imaging (MRI) scan can show the size of any tumor.
  • Eye and visual tests can assess if the tumor is pressing on the optic nerve.
  • If you are confirmed as having acromegaly, other tests will be needed to see if the tumor is causing a lack or excess of other hormones made by the pituitary.
  • Other tests may include chest X-ray, electrocardiogram (ECG) and X-rays of some of your joints.

Complications

Common complications of acromegaly are:

  • High blood pressure (hypertension)
  • Cardiovascular disease, particularly enlargement of the heart (cardiomyopathy)
  • Osteoarthritis
  • Diabetes mellitus
  • Precancerous growths (polyps) on the lining of your colon
  • Sleep apnea, a condition in which breathing repeatedly stops and starts during sleep
  • Carpal tunnel syndrome
  • Reduced secretion of other pituitary hormones (hypopituitarism)
  • Uterine fibroids, benign tumors in the uterus
  • Spinal cord compression
  • Vision loss

Treatment

Management goal in acromegaly is to reduce the level of growth hormone in the blood to normal, and to reduce the size of an enlarged tumor. Many of the symptoms and features of acromegaly will reverse or improve with successful treatment (apart from any fixed extra bone growth that had occurred).

Surgery

The most common treatment is to remove the adenoma by surgery. This is done using very fine instruments. Doctors can remove most pituitary tumors using a method called transsphenoidal surgery. In this procedure, your surgeon works through your nose to extract the pituitary tumor. Removing the tumor can normalize GH production and eliminate the pressure on the tissues surrounding your pituitary to relieve associated signs and symptoms. In some cases, your surgeon may not be able to remove the entire tumor. This may result in persistently elevated GH levels after surgery, requiring further medical or radiation treatments.

This is a complex procedure, so it’s important to choose a surgeon experienced in performing this type of surgery. Usually, the more experienced the surgeon, the better the final outcome.

Medication

If surgery is not possible, or not wanted medication can be used. It is also used whilst waiting for surgery or radiotherapy. It can also be used in cases where surgery fails to remove the tumor totally and the level of growth hormone remains high.

  • Somatostatin analogues (octreotide and lanreotide). These medicatins reduce the level of growth hormone to normal in over half of cases, and reduce the size of the tumor in about 8 in 10 cases. However, these medicines need to be given as an injection. They work in a similar way to somatostatin which is a hormone that prevents growth hormone from being released from pituitary cells. These medicines used to be injected several times a day. However, longer-acting preparations are now available as monthly or fortnightly injections. Side-effects are not common with these medicines. Some people develop abdominal pains and diarrhea, but these usually wear off with time. Gallstones can also occur but rarely cause problems.
  • Dopamine agonists (such as cabergoline, bromocriptine and quinagolide). These medications can be taken as tablets. They work by preventing the release of growth hormone from tumor cells. However, they only work well in about 1 in 5 cases. Side-effects such as feeling sick and dizzy are also quite common.
  • Pegvisomant. This medication is taken as a daily injection. However, unlike the other medicines listed above, it does not act directly at the pituitary. Pegvisomant works by blocking the action of growth hormone on your body’s cells. Therefore, although many of the symptoms of growth hormone excess will be eased, it does not reduce the size of the tumor and headaches are not eased.
Radiotherapy

Therapy with radiation is an option to reduce the size of the tumor and hence reduce the production of growth hormone. Radiotherapy focuses high-intensity radiation at your pituitary tumor to destroy the abnormal cells. It may be used if you are not able to have surgery, or if surgery was only partially successful. However, it can take months or years after the radiotherapy is given for the level of growth hormone to reduce to normal. You can take medication whilst waiting for the effects of radiotherapy to work.।

पA possible side-effect of pituitary radiotherapy is damage to other normal pituitary cells. This can cause a reduced level of some other hormones. However, if this occurs you can take replacement hormone therapy.