New Diagnosis for Very Short Kids
Growth Factor Deficiency Stunts Growth of 30,000 U.S. Kids
Sept. 10, 2004 -- A study of very short American kids shows that many of them suffer from a potentially treatable problem.
Not every short child has a problem. But children who are among the shortest 2.5% of their age group clearly aren't growing the way they should. Some of these kids don't make enough growth hormone -- and treating them with growth hormone restores normal growth patterns.
Despite this success, many kids with short stature don't respond to growth hormone treatment. For many of these kids, the reason now seems clear. They suffer from too little of another kind of growth hormone, called insulin-like growth factor type 1, or IGF-1, according to a report at last week's 12th International Congress of Endocrinology meeting in Lisbon, Portugal.
The report, based on data collected in the U.S. National Cooperative Growth Study, comes from Tercica Inc. in South San Francisco, Calif. Tercica makes recombinant IGF-1, currently being tested as a treatment for IGF-1-deficient children.
"We usually say that out of every 10 kids referred to a doctor for short stature, one walks away with a prescription for growth hormone. So 90% walk away with basically nothing," Tercica CEO John Scarlett, MD, tells WebMD. "There is another group of patients who are not growth-hormone deficient for whom we now have another treatable condition: primary IGF-1 deficiency. There are some 30,000 of these kids in the U.S. today that potentially can respond to treatment."
Long Chain of Events, Short Stature
Growth hormone comes from the pituitary gland in the brain. When it reaches liver cells, it flips the master growth switch called the growth hormone receptor. This activates the gene for IGF-1, which starts IGF-1 flowing to the cartilage and bones, where it stimulates growth.
If there simply isn't any growth hormone coming from the brain, giving a kid growth hormone jump-starts this process. But many short-stature kids have plenty of growth hormone. It just isn't doing its job. Either it isn't flipping the growth-hormone-receptor switch, or else something is wrong with the IGF machinery. In either case, treatment with IGF-1 might help. It might bypass the growth-hormone receptor. Or it might bypass the clog in the IGF system. Either way, the right signal would go to the bone and cartilage.
At least, this should happen in theory. Does it happen in real life? Earlier this year, Tercica researchers reported results from a 10-year clinical trial of their recombinant human IGF-1 injection product. Sure enough, kids started to grow.
"The children in this study were only growing an inch a year -- half the normal growth rate," Scarlett says. "In the first year of treatment, they did catch up growth. Eventually they settled in at twice their previous growth rate."