Researchers have found a way to identify which young adults with childhood-onset growth hormone deficiency will benefit from continued growth hormone replacement therapy. The results of the new study will be presented Tuesday, June 17, at The Endocrine Society’s 90th Annual Meeting in San Francisco.

“We found it is now possible to discriminate between transient and permanent growth hormone deficiency of childhood onset,” said a study coauthor, Mohamad Maghnie, MD, of the pediatrics department at the University of Genova in Italy.

Replacement of growth hormone, the hormone that stimulates body growth in childhood, can help children who are deficient in this hormone attain normal or close-to-normal adult height. At that time, treatment ends. However, in some patients, especially those with structural pituitary abnormalities, the condition is permanent. If growth hormone therapy is not restarted, they are at increased risk of health problems, such as cardiovascular diseases, reduced bone and muscle mass, excess body fat, low energy, and high cholesterol.

The diagnosis of growth hormone deficiency most often relies on the insulin tolerance test, in which the patient receives insulin after an overnight fast and undergoes to repeated blood sampling for growth hormone measurement. Doctors also may measure blood levels of insulin growth factor-1 (IGF-1), a growth factor regulated by growth hormone.

Patients between the ages of 16 and 25 years, however, do not meet current pediatric or adult diagnostic criteria for these tests, as demonstrated by a previous paper of Mahgnie’s group. For patients in this so-called “transition age,” the authors proposed a new diagnostic cut point value for these tests. Based on this previous research, several medical associations developed consensus guidelines last year that proposed adopting their cutoffs for the diagnosis of permanent growth hormone deficiency. However, further study was needed to confirm the recommendations.

The new study involved 90 subjects with an average age of about 18 years. All had childhood-onset growth hormone deficiency and had stopped growth hormone therapy for at least a month after reaching adult height. No subject had acquired growth hormone deficiency due to cancer or cancer treatment. The researchers used, as cutoffs to indicate growth hormone deficiency, a peak growth hormone value after the insulin tolerance test of less than 6 micrograms per liter (or less than 6 nanograms per milliliter) and an IGF-1 value less than −1.65 SDS (standard deviation score).

A peak growth hormone value less than six correlated with a low spontaneous nocturnal growth hormone level measured on blood testing, which verified the reliability of the new cutoff, the authors found. Also, nearly 83 percent of the subjects (24 of 29) with a peak growth hormone less than 6 had congenital pituitary abnormalities, as shown by magnetic resonance imaging (MRI). Structural pituitary abnormalities were present in only 11.5 percent of the subjects (7 of 61) whose peak growth hormone was higher than six, Maghnie said.

“Young adult patients with test values indicating insufficient growth hormone should restart growth hormone replacement therapy,” Maghnie advised.

External funding for this study came from Italy’s Ministry of University and Research.

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Founded in 1916, The Endocrine Society is the world's oldest, largest, and most active organization devoted to research on hormones and the clinical practice of endocrinology. Today, The Endocrine Society's membership consists of over 14,000 scientists, physicians, educators, nurses and students in more than 80 countries. Together, these members represent all basic, applied, and clinical interests in endocrinology. The Endocrine Society is based in Chevy Chase, Md. To learn more about the Society, and the field of endocrinology, visit our web site at www.endo-society.org.