The Use Of Growth Hormones In Children

Our pediatrician is worried about my son’s size, since he has fallen below the third percentile for his age. He wants to take x-rays for bone age and refer him to an endocrinologist, and has mentioned that he might be a “pituitary dwarf.” Can you help me to understand what is going on?

Short stature and slow growth in children can have many causes, ranging from the familial — that is, having short parents — to poor nutrition, psychosocial deprivation, or chronic heart, lung, kidney or infectious diseases. Pituitary dwarfism is not a common cause of such short stature, but since it is a treatable cause, it is important to rule out the possibility.

Pituitary dwarfs have slow growth and short stature with normal body proportions. This is in contrast to the more common achondroplastic dwarfs, who have a defect in cartilage and bone formation, and tend to have short arms and legs with a relatively long trunk. Achondroplasia is not a treatable condition at this time.

Pituitary dwarfism is caused by a deficiency of growth hormone, one of the many hormones produced by the anterior part of the pituitary gland. This deficiency may be caused by a tumor that destroys the pituitary or it may be idiopathic, meaning that the cause is not known. The child’s height is reduced for his age, and the growth velocity, the amount of growth that occurs per year is reduced. The bone age is usually more than two years behind the child’s actual age. The x-ray that the doctor wants to order is probably an x-ray of the child’s hand. Bone age is measured by comparing an x-ray of the child’s hand with a table showing how the bones appear at different ages in normal children.

Growth hormone levels can be measured in the blood, as can a major product of growth hormone called insulin-like growth factor-1 (IGF-1). Random measurements of growth hormone are not very helpful, however, since it is one of the hormones that is secreted in spurts; and often, particularly in younger children, the test may not find any hormone in the blood, even in a normal child. Growth hormone secretion is stimulated by low blood sugar, exercise, or stress. Provocative testing, measuring the blood level of the hormone after the blood sugar has been lowered by giving insulin, may be necessary to confirm the diagnosis.

It is also important to evaluate the other hormones that are dependent on the pituitary for stimulation. These include thyroid hormone, the adrenal hormone hydrocortisone, and — if the child is an adolescent — the two hormones that stimulate the ovaries and testes. Delayed onset of puberty will usually be present with growth hormone deficiency if it has not been corrected by adolescence.

Treatment of confirmed growth hormone deficiency is now fairly straightforward with daily injections of the hormone under the skin, similar to insulin injections. Adverse side effects are not common. The hormone is now made by recombinant DNA technology, and is not actually extracted from human pituitary glands as in the past. Nonetheless, it is very expensive, and treatment can run around $10,000 per year or more. If begun in childhood, treatment will often allow the child to achieve a “normal” height that one might expect based on heredity.

Some experts recommend this treatment for short children who have the clinical appearance of pituitary dwarfism, yet have normal blood hormone studies — that is, children who do not have a demonstrable deficiency of growth hormone. This treatment is continued for six to twelve months, and is continued longer if there is a substantial increase in the growth velocity. This approach is quite controversial, since it is expensive and it may convince a normal child that there is something medically wrong.

There has been some recent interest in using growth hormone injections in the elderly. Growth hormone levels do decline with age, and injections of it will cause an increase in muscle and bone mass, and a loss of fat. Some short-term studies have demonstrated these changes, but as yet there have been no long-term studies that would enable doctors to evaluate possible detrimental side effects, such as the stimulation of cancer growth. Such hormone supplements are, therefore, seldom prescribed.

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