Growth Disorders

One of the remarkable roles of the endocrine system is the regulation of growth and development throughout our bodies. This work is directed by the pituitary gland — perhaps the most important “master gland” of the endocrine system. A small oval-shaped organ at the base of the brain, the pituitary gland releases many types of hormones into the blood stream. One of these is growth hormone (GH) called somatotropin. Once in the blood, GH travels to bone, muscle, and other tissues where it has many effects. The hypothalamus, a small structure located at the base of the brain just above the pituitary, controls the release of growth hormone by the pituitary gland. The principal stimulator of growth hormone secretion is called the growth hormone-releasing hormone.

In children, for example, GH stimulates linear growth, or height. It is also important for the development of muscle and bone, and the distribution of body fat throughout the body. In adults, GH affects energy, muscle strength, bone health, and psychological well being. Having either too much or too little GH can cause health problems.

In some cases, individuals may have too much GH, a condition called acromegaly in adults. Acromegaly is usually caused by a non-cancerous pituitary gland tumor of the pituitary gland. In the rare instances when it occurs, too much GH in children causes gigantism.

A more common growth disorder is growth hormone deficiency (GHD). This is the condition of having too little GH. There are several possible explanations for its occurrence:

  •  A child can be born with GHD.
  • The condition also may arise because of damage to the hypothalamus or pituitary gland as a child or adult because of a tumor, an infection, or radiation to the brain — usually for the treatment of a tumor.
  • A deficiency in GH may also have an undefined cause. (In this case, it is said to be of idiopathic origin.

 

Symptoms

Adults usually have large hands and feet, thick lips, coarse facial features, a protruding forehead and jaw, and widely spaced teeth. Often patients perspire excessively. Many of the signs and symptoms evolve slowly, so the diagnosis is often made years after the symptoms begin.

There are numerous symptoms that may be associated with growth disorders:

  • Headaches
  • Numbness or burning of the hands or feet; carpal tunnel syndrome
  • Glucose intolerance, (also known as insulin resistance, this condition puts one at risk for type 2 diabetes)
  • Cardiac dysfunction (heart attack, heart failure, or enlarged heart)
  • High blood pressure
  • Goiter (enlarged thyroid gland)
  • Sleep apnea
  • Tiredness
  • Menstrual disorders (irregular bleeding; absence of periods)
  • Decreased libido (low sex drive)
  • Vision problems (tunnel vision; vision loss)
  • Psychological problems (depression; anxiety)

In children with gigantism, the main symptom is increased linear growth (height) causing extremely tall stature. This can also be associated with obesity, increased head size (macrocephaly) and a prominent forehead (also called frontal bossing).

 

Growth Hormone Excess: Treatment Options

Because excess GH — acting alone or together with excess IGF-1 — produces adverse health effects, eliminating the hormone imbalance and reducing the levels to normal is desirable. Surgery, medication and/or irradiation of the pituitary gland may be appropriate to achieve these goals.

Surgery. The most common cause of GH hypersection is a non-cancerous tumor of the pituitary gland, which produces GH. For these patients, surgery to remove the tumor is the treatment of choice. Unfortunately, in other cases there is a generalized enlargement of the pituitary gland, which is called pituitary hyperplasia. This makes surgery impossible since there is not a discrete area to be removed.

If surgery does not normalize the GH level, or if a patient is not a candidate for surgery, other therapies are used. Medication and irradiation of the pituitary gland are options as primary or supplemental therapy.

Medications. Three types of drugs are now available for the treatment of GH excess — somatostatin analogues, GH receptor antagonists, and dopamine agonists. These medications do not “cure” the disorder but work, instead, to reduce levels of GH or IGF-1. These medications must be taken for life if surgery or irradiation fails to eliminate the cause of GH excess.

Pituitary Irradiation. Radiation therapy is another therapeutic approach for patients with acromegaly, who have undergone pituitary surgery and still have excess GH. This remaining overproduction of GH may occur if the pituitary gland tumor removed during surgery had spread beyond the pituitary gland. Because complete removal of invasive tumors is often challenging, additional therapy may be needed to achieve normal GH and IGF-1 levels.

Although pituitary irradiation can ultimately achieve complete remission, its disadvantage is the time needed to reach that goal. Conventional radiation therapy may take 10 years or longer to be fully effective. Newer methods of focused delivery — such as gamma knife, proton beam, or linear accelerator — of a high dose of radiation to the tumor often affect an earlier remission than the conventional method. Unfortunately, there still may be a significant delay.

Although it takes longer to attain remission with irradiation than with medications, once remission is reached, the effects of irradiation are permanent. Patients may need to take medication until the radiation therapy achieves its effect.

Unlike in adults, radiation is consisted a last resort in children with GH excess, as there as concerns about its effects on the developing brain.