HIGH GROWTH HORMONE LEVELS IN CLINICALLY SHORT STATURE CHILDREN

Abstract

Background: Growth Hormone (GH) is secreted from the anterior pituitary gland. It binds toreceptors on the surface of target cells, stimulates production of Insulin-like growth factor-I (IGFI) leading to growth of almost all tissues of the body capable of growing. Growth failure (heightbelow 3rd centile) occurs in children who do not secrete sufficient amount of GH. In somechildren, however, short stature is present in the presence of high levels of GH in their blood andthey also secrete normal to increased amounts of GH in response to stimulation tests when testedfor possible deficiency of GH. This condition is known as GH resistance syndrome or Laronssyndrome (LS). Methods: All patients after a thorough clinical evaluation underwent GHevaluation protocol as follows. On arrival in the lab a blood sample was collected for basal GHlevel in each patient. Screening was performed by subjecting the patients to exercise stimulationtest and/or L-dopa stimulation test. Patients with GH deficiency underwent insulin tolerance test(ITT) after one week for confirmation. All the basal and post-stimulation samples were analyzedfor GH levels. A level below 10mIU/L indicated GH deficiency, between 10-20mIU/L asborderline and an adequate response was defined as a GH >20mIU/L. Patients with a basal GHlevel of >20mIU/L and/or a post-stimulation level of >40mIU/L were arbitrarily considered ashaving exaggerated GH levels. This article evaluates the high plasma growth hormone levelsamong clinically short stature children undergoing growth hormone stimulation tests. Results:Two hundred ninty-three patients reported for GH evaluation. Twenty were excluded for variousreasons. Thus 273 patients were included for GH evaluation out of which 66(24.2%) showed GHdeficiency, 89(32.6%) were borderline while 118(43.2%) patients exhibited adequate response,with GH levels of >20mIU/L. A number of patients unexpectedly showed very high GH levels onscreening tests. Out of 118 patients, 21 showed either very high basal levels of >20mIU/L and/or amuch-exaggerated response to stimulation tests with levels more than about 40mIU/L. Closeconsanguinity was found in 67% of patients showing very high GH levels. Conclusion: Somechildren with idiopathic short stature may show high levels of GH during their evaluation for GHdeficiency. We identified a considerable number of such patients. These patients require furtherinvestigations.KEY WORDS: Growth Hormone, Resistance Syndrome, Short Stature, Exercise, L-dopa, InsulinTolerance Test (ITT).