Growth hormone deficiency occurs when the pituitary gland does not produce enough growth hormone.
- Growth hormone deficiency is the most common pituitary hormone deficiency and is accompanied by poor overall growth and short stature.
- Other symptoms of growth hormone deficiency depend on the child's age and the cause of the deficiency.
- Most often, doctors do not find a cause for growth hormone deficiency, but sometimes it is caused by a congenital disorder or brain tumor.
- The diagnosis is based on a physical examination, review of the child's growth charts, and testing that may include x-rays, blood tests, genetic tests, stimulation tests, and imaging tests.
- Treatment typically includes hormone replacement therapy.
Hormones are chemical messengers that affect the activity of another part of the body. Growth hormone regulates growth and physical development and is produced by the pituitary gland, which is located at the base of the brain.
Pituitary: The Master Gland
The pituitary, a pea-sized gland at the base of the brain, produces a number of hormones. Each of these hormones affects a specific part of the body (a target organ or tissue). Because the pituitary controls the function of most other endocrine glands, it is often called the master gland.
If the pituitary gland does not produce enough growth hormone, abnormally slow growth and short stature with normal proportions can result. Children who are deficient in growth hormone can also be deficient in other pituitary hormones such as thyroid-stimulating hormone, adrenocorticotropic hormone, follicle-stimulating hormone, and luteinizing hormone (this disorder is called hypopituitarism).
Short stature is defined as height below the 3rd percentile for the child’s age (according to standard growth charts for age and height). In addition to a deficiency of growth hormone, short stature can occur for other reasons. For example, most children and adolescents who have short stature are short because their families are short, or because their growth spurt came at the late end of the normal range of time for such development. Some children are short because of poor weight gain and poor nutrition or because they have certain chronic illnesses that affect the thyroid, heart, lungs, kidneys, or intestines. Other children have genetic disorders that affect bone growth.
A deficiency in growth hormone production most often has an unknown cause, but about 25% of cases have an identifiable cause, including
- Congenital disorders
- Brain tumors or injuries
- Infections (such as meningitis and tuberculosis)
Symptoms of Growth Hormone Deficiency
Symptoms of growth hormone deficiency depend on various factors such as the child's age and the cause.
Children have poor overall growth rates, usually below 2 inches (5 centimeters) per year, and most have short stature but normal upper and lower body proportions. Some children may have a delay in tooth development or a delay in puberty.
Other abnormalities may be present depending on the cause of the growth hormone deficiency. Newborns with growth hormone deficiency may have low blood sugar (hypoglycemia), jaundice (hyperbilirubinemia), or other congenital abnormalities such as a small penis (micropenis) in males or face defects (such as a cleft palate). Children may also have symptoms of other hormone deficiencies such as central hypothyroidism.
Diagnosis of Growth Hormone Deficiency
- A doctor's evaluation of growth criteria and past medical history of disorders known to cause slow growth
- Blood and other laboratory tests
- Sometimes genetic testing
- Magnetic resonance imaging
- Usually stimulation tests
Growth hormone levels in the blood vary widely and are not as useful as other hormone levels in determining why a child's growth is decreased. Thus, doctors make the diagnosis based on a collection of findings.
First, doctors measure the child's height and weight and plot the measurements on age-specific growth charts to determine whether they are growing too slowly. Then they often do x-rays of bones in the hand. Such x-rays can show if the bones are developing normally for the child's age. Children who are simply short have normal bone development for their age. Children who have growth hormone deficiency have delayed bone development. Delayed bone development can also occur in other conditions, such as hypothyroidism and delayed puberty.
It is difficult for doctors to assess growth hormone production because growth hormone production fluctuates throughout the day. As a result, measurement of random growth hormone levels is often not helpful. Instead, doctors do blood tests to measure levels of other substances in the blood that are stimulated by growth hormone. Such substances include insulin-like growth factor 1 and insulin-like growth factor binding protein 3. However, these substances may be affected by other conditions, such as hypothyroidism, celiac disease, and undernutrition, so doctors may do tests to rule out these conditions.
Other laboratory tests are done to look for other causes of poor growth (such as thyroid, blood, kidney, inflammatory disorders, and immune disorders). Genetic testing may be done if doctors suspect the child has a specific syndrome (such as Turner syndrome).
If test results suggest that the child has a pituitary disorder, imaging tests of the brain using magnetic resonance imaging (MRI) may be done to look for structural abnormalities in the pituitary gland and for tumors.
If children have no other cause of poor growth and their growth hormone levels are low, doctors typically do a stimulation test. The stimulation test involves giving drugs that stimulate growth hormone production, then measuring growth hormone levels over several hours.
Treatment of Growth Hormone Deficiency
- Replacement of growth hormone
- Sometimes replacement of other hormones
Children are given injections of synthetic growth hormone. The hormones are given until children reach an acceptable height or until children do not grow more than 1 inch (about 2.5 centimeters) in a year. During the first year of treatment, children may grow up to 4 to 5 inches (10 to 12 centimeters), but individual responses vary. Children do not usually have side effects from growth hormone therapy, although some develop mild swelling of the limbs that usually resolves quickly or infrequently develop more serious side effects such as increased pressure in the brain (idiopathic intracranial hypertension or a problem in the upper thigh bone that can show up as knee or hip pain or limping (slipped capital femoral epiphysis).
Growth hormone also may be used to increase height in children who are short but have normally functioning pituitary glands, but this use is controversial. Some parents feel that short stature is a disorder, but many doctors do not approve of the use of growth hormone in these children. Regardless of the cause of short stature, growth hormone is effective only if given before the bones stop growing.
If identified, some brain tumors can be removed surgically, but children are at high risk of hypopituitarism because surgery may damage the pituitary. Children who have hypopituitarism are given hormones to replace the ones they are lacking (see treatment of hypopituitarism).