Some people who were treated for cancer during childhood may develop endocrine (hormone) problems as a result of changes in the function of a complex system of glands known as the endocrine system.
The endocrine system is a group of glands that regulate many body functions including growth, puberty, energy level, urine production, and stress response. Glands of the endocrine system include the pituitary, hypothalamus, thyroid, adrenals, pancreas, ovaries (in females), and testes (in males). The hypothalamus and pituitary are sometimes called the “master glands” because they control many other glands in the endocrine system. Unfortunately, some treatments given for childhood cancer can damage the endocrine system, resulting in a variety of problems.
Hormones are chemical messengers that carry information from the endocrine glands through the bloodstream to the body’s cells. The endocrine system makes many hormones (such as growth hormone, sex hormones, adrenal and thyroid hormones) that work together to maintain specific bodily functions.
Growth hormone (GH) is made by the pituitary gland. In order for children to grow to their full height potential, they need adequate amounts of GH. GH works in combination with thyroid hormone, exercise, proper nutrition, and rest to help children and teenagers grow. GH also helps maintain blood sugar levels and is necessary for the normal development of teeth. In addition to helping with bone growth, GH affects how well the heart and blood vessels work; how the body uses fat, makes muscle, and strengthens bones; and overall health throughout life.
In healthy people, GH production continues into adulthood. Adults need small amounts of GH to maintain proper amounts of fat, muscle, and bone. GH may also play a role in stimulating and controlling areas of the brain that regulate mood and emotion.
Growth Hormone Deficiency
Cancer treatments, such as radiation or surgical procedures to structures in the head or brain, may cause the glands that control growth to malfunction. As a result, the pituitary gland may not make enough GH, resulting in growth hormone deficiency.
Signs and Symptoms of Growth Hormone Deficiency
A noticeable slowing of growth (height) is one of the most obvious signs of GH deficiency in children. A GH deficient child usually grows less than 2 inches per year. Children with GH deficiency are smaller and tend to look younger than their peers, but they usually have normal body proportions.
Adults who have GH deficiency may have a variety of different physical symptoms, such as thinning of the bones, decreased muscle strength, increased body fat, or high blood cholesterol levels. Adults may also have emotional symptoms such as feeling tired, anxious, irritable, pessimistic, or unmotivated.
Risk Factors for Growth Hormone Deficiency
- Cancer treatment before reaching adult height, especially if treatment occurred when a child was very young.
- Radiation to the head or brain, especially in doses of 18 Gy (1800 cGy/rads) or higher, including the following fields:
- Cranial (whole brain), especially if given before bone marrow or stem cell transplant
- Craniospinal Nasopharyngeal (nose and throat)
- Oropharyngeal (mouth and throat)
- Eye and Orbit
- Infratemporal (midfacial area behind the cheekbones)
- Total body irradiation (TBI), especially at a dose of 10 Gy (1000 cGy/rads) or higher in a single fraction, or 12 Gy (1200 cGy/rads) or higher in fractionated (split) doses
- Surgery to the brain, especially the central region of the brain where the pituitary gland is located (suprasellar region)
All children’s cancer survivors should have a yearly physical examination including measurement of height and weight, and assessment of pubertal status, nutritional status, and overall well-being. For patients with the risk factors listed above, this screening should be done every 6 months until growth is completed.
Evaluation for other potential causes of growth problems, such as low thyroid function, should also be explored. If GH deficiency is suspected, patients will probably be referred to an endocrinologist (doctor who specializes in hormone problems). The endocrinologist will do more specific tests to evaluate the problem.
Treating Growth Hormone Deficiency
If GH deficiency is detected, the endocrinologist will suggest treatment options. Usually, this involves supplementing or replacing the GH that the pituitary gland is not making on its own. Called synthetic GH, this supplement is given by injection. GH is usually given for several years, until the person reaches acceptable adult height or maximum potential. The endocrinologist can provide a realistic expectation about growth potential. Treatment options for GH deficiency that persists into adulthood should be discussed with the endocrinologist.