Diagnosis of growth hormone deficiency in adults b... - GHRP-6 Study

Key Findings

GHRP‑6 alone produced a clear difference in GH peaks between deficient (≈1.3 µg/L) and sufficient (≈25.7 µg/L) subjects.

Combining GHRP‑6 with GHRH gave even larger peaks (≈4 µg/L vs ≈55 µg/L).

Cut‑off values of <7 µg/L for GHRP‑6 alone and <13 µg/L for the combo correctly identified all GH‑deficient patients.

Only mild flushing was reported as a side effect.

Practical Outcomes

You can use a single GHRP‑6 injection (1 µg/kg) to gauge your own GH production without the dangerous insulin tolerance test. Measure GH levels over the next 90 minutes; if the peak is under 7 µg/L you likely have a deficiency. Adding GHRH improves the signal, with a cut‑off of 13 µg/L, and the protocol is safe with only mild flushing as a side effect.

Summary

A study showed that giving the peptide GHRP‑6 (1 µg/kg) – either alone or together with GHRH – can reliably tell if an adult has growth‑hormone deficiency, matching the gold‑standard insulin tolerance test but with far fewer risks.

Abstract

The diagnosis of GH deficiency in adults should be made using provocative testing of GH secretion. The insulin tolerance test (ITT) is recommended as the gold standard investigation. Because of the risk of serious complications, patients with epilepsy or known ischemic heart disease should not undergo this test. GHRP-6 is a synthetic hexapeptide that releases GH by binding to specific hypothalamic and pituitary receptors. We assessed the diagnostic capability of GH stimulation by GHRP-6 alone or in combination with GHRH in comparison to the results of an ITT. Twenty patients underwent an ITT for suspected pituitary or adrenal disease. Either GHRP-6 (1 microg/kg) alone, or GHRP-6 in combination with GHRH (1 microg/kg) were administered on different days. Blood samples were obtained during a subsequent 90-min period for measurement of GH. Ten patients had a GH peak response of less than 3 microg/l during ITT and were considered growth hormone deficient (GHD). The GH mean peak (+/-S.E.M., range) in this group was 0.7 microg/l (+/-0.3, 0.1-2.9) compared with 14.5 microg/l (+/-3.5, 3.8-40.8) in the group of patients with a GH peak response of more than 3 microg/l (growth hormone sufficient (GS)). For the GHRP-6 test, the GH mean peak was 1.3 microg/l (+/-0.6, 0.1-6.7) in the GHD group versus 25.7 microg/l (+/-5.5, 7.7-54.2) in the GS group. After GHRP-6+GHRH, the GH mean peaks were 4.0 microg/l (+/-1.3, 0.2-11.9) versus 54.7 microg/l (+/-11.1, 13.9-136.0) respectively. During administration of GHRP-6, the only side effects observed were flush symptoms. Peak GH levels below 7 microg/l for the GHRP-6 test and below 13 microg/l for the combined GHRP-6+GHRH test identified all patients with GH deficiency correctly as defined by ITT. The results suggest that testing with GHRP-6 or GHRP-6+GHRH is as sensitive and specific as an ITT for the diagnosis of adult GH deficiency.

Study Information

Provider

pubmed

Year

2002

DOI

10.1530/eje.0.1460667