OR07-2 Simultaneous stimulation of human 20 kDa growth hormone and 22 kDa growth hormone secretion by ghrelin

Abstract

The World Anti Doping Agency has banned the use of recombinant human growth hormone (rhGH). Regardless, rogue athletes may use rhGH in pursuit of improved performance. Current immunoassaybased detection of illicit use of rhGH is complicated by the short half-life of injected rhGH, by the chemical identity of rhGH and a native growth hormone (GH), and by the physiologically high peaks of GH that occur with the pulsatile secretion of GH by a normal pituitary. We hypothesized that injection of rhGH changes the expression patterns of GHmessenger RNA (mRNA) in circulating white blood cells and of microRNA (miRNA) in plasma. Objective: To measure circulating GH mRNA and miRNAs in humans. Methods: We used reverse-transcription quantitative polymerase chain reaction (RT-qPCR) with nested primers to detect and quantify GHmRNA.We usedmiRNAmicroarrays to identify rhGH-dependent miRNA expression and then measured the concentrations of selected miRNAs by RT-qPCR. Following Institutional Review Board approval, we obtained whole-blood or plasma, from 9 healthy volunteers and from 36 patient volunteers. All patients had known or suspected disorders of growth hormone production including panhypopituitarism treated with physiologic doses of rhGH (0.2 to 0.8mg/day) and acromegaly. Results: GH mRNA was quantified in blood from all healthy volunteers and patients with disorders of GH at concentrations ranging from 36 to 4815 copies/100 mL blood. The intra-individual GH mRNA concentration varied less than 3-fold in 17 samples collected over the period of one year in a healthy, athletic volunteer; however, variability increased markedly in the group with pituitary disorders. Initially, 9 specimens from: 3 patients receiving therapeutic growth hormone replacement, 4 patients with acromegaly, and 2 normal controls, were subject to plasma-derived miRNA microarrays. Of 1105 miRNA’s measured in each microarray, 3 were present in plasma of all rhGH replacement users and undetectable in all patients with acromegaly and normal controls. Conclusions: The narrow intra-individual range of its concentration suggests that GH mRNA in blood is not present as a result of pulsatile secretion and thus is worthy of study as a marker of doping with supraphysiologic amounts of rhGH. Further investigation of miRNA in plasma should be performed on samples obtained before and after administration of supraphysiologic amounts of rhGH to confirm the preliminary results in patients receiving therapeutic replacement doses of rhGH.