Diagnosis of Growth Hormone Deficiency in Adults

Abstract

Adult growth hormone deficiency (GHD) has a wide spectrum of clinical presentations including abnormal body composition, increased blood pressure, increased body weight, adverse lipid profiles, increased coagulability, and increased markers of inflammation, all associated with an increased cardiovascular morbidity and mortality. Detection of GHD is important, especially as successful GH replacement therapy improves the adult GHD syndrome and is accompanied by a significant increase in quality of life. Health authorities in many countries have approved the therapeutic use of GH in adult hypopituitary patients in whom GHD has been identified. The identification of adults with GHD remains challenging due to the episodic nature of GH secretion (pulsatile secretion) and multiple GH samples over 24 h are not practical as diagnostic procedure. For this reason in adults with known pituitary disease, diagnostic testing involves provocative tests of GH secretion. The insulin tolerance test (ITT) is regarded as the standard test of choice. Reproducibility, demanding surveillance during the test, and safety issues under some circumstances may be of some concern. Other more powerful provocative tests like the GH-releasing hormone (GHRH) + arginine and GHRH + GH-releasing hexapeptide 6 (GHRP-6) have gained acceptance after being evaluated in a large series of patients and controls. Glucagon test has yet to be evaluated in large series of patients and controls, but has already gained popularity particularly in the US after shortage of GHRH supplies. In adult patients with known pituitary disease, the presence and severity of GHD are related to the number of additional pituitary hormone deficits so that in panhypopituitary patients GH stimulation tests may be unnecessary. In that situation, insulin-like growth factor 1 (IGF-1) may be a useful diagnostic tool. Otherwise, considerable overlap exists for IGF-1 levels between normal subjects and those with GHD. Therefore, IGF-1 is not a reliable marker for diagnosis of GHD. When focused on childhood-onset GHD, these young adults who had previously received GH replacement in childhood need to be reevaluated for GH status.KeywordsGrowth hormoneGrowth hormone deficiencyHypopituitarism