Synthetic Growth Hormone

Q:  I've been researching the subject of synthetic human growth hormones but have found very little information. My son, who is 12 years old, is often mistaken for someone three to four years younger. He has been growing an average of one inch a year for the last several years. His pediatrician seems unconcerned, though growth charts indicate 99% of kids his age are taller than he.

What is your opinion of synthetic growth hormone, and has it been used safely ? I worry about side effects.

A:  Growth hormone, which is secreted by the pituitary gland, was discovered in 1956 and first used to treat dwarfism two years later. Back then the hormone was derived from the brains of human cadavers. In 1985 genetically engineered growth hormone was finally approved for use.

True growth hormone deficiency is very rare, occurring in only about 20,000 children in this country. Dr. David Wyatt, Chief of Pediatric Endocrinology at the Medical College of Wisconsin, told me that in over 15 years of a large referral practice, he has discovered only about 175 cases, or about 1 child a month. These children then require a daily injection of growth hormone, which causes no side effects, but is very expensive, costing about $15,000 - 40,000 a year.

Growth hormone given to "normal" children probably will have little effect on height, although a Stanford University endocrinologist, Raymond Hintz, has given growth hormone to "severely short" but otherwise healthy children. They added an average of 3 inches to their projected adult height. He believes that such treatment can help prevent psychological damage that results from being small. Other studies have not proven that premise.

Each person has a genetic target range of height, and one can get a good idea of your son's potential height by first considering parental height. Are both of you average height, or is one on the shorter side? Next, how does he compare to other 12 year-old-boys? You mentioned that he is in the lower 1% on the growth charts, but remember that the lowest and the highest 1% are extremes of a NORMAL range.

According to Dr. Wyatt, the most critical step in evaluating your son is to look at his growth chart. Average growth rates are about 2 1/3 inches per year at age 7, slowing down to 2 inches a year by age 11. Everyone has a dip in growth rates just before puberty, but the later you enter puberty, the more you slow down, so that "late bloomers" may grow at slower rates as low as 1 inch a year. Your son, who has had similar rates of growth, may fall into that category. By the end of puberty, late bloomers usually have caught up to early bloomers.

The odds are great that your son does not have a growth hormone deficiency. Dr. Wyatt estimates that 50% of the kids he evaluates don't need any further workup after he analyzes their growth charts. The remainder are usually watched for a full year before growth hormone therapy is started - if at all.

"Dear Doctor" is a compilation of patient questions answered by doctors from the Medical College of Wisconsin.