Further evidence for a role of human growth hormone (hGH) in the control of penile erection in the adult male
Stefan Ückert (DE), Armin Becker (DE), Andreas Bannowsky (DE), Markus Kuczyk (DE)
[Ückert] Hannover Medical School, [Becker] Ludwig Maximilian University, [Bannowsky] Imland Klinik GmbH, [Kuczyk] Hannover Medical School
Context: Examine the role of GH in the mechanism of penile erection. Objectives: Human growth hormone (GH) has been suggested to be involved in sexual maturation and play a role in male reproductive function. Methods: Effects of GH were investigated on electrically (EFS)-induced relaxation of isolated penile erectile tissue in the absence and in presence of ODQ (guanylyl cyclase inhibitor) and L-NOARG (nitric oxide synthase inhibitor, 10 µM). Effects of GH on the production of cGMP in the absence and presence of ODQ and L-NOARG were also elucidated. Blood samples were drawn simultaneously from the corpus cavernosum and a cubital vein during the penile conditions flaccidity (Fl), tumescence (Tu), rigidity (Ri, healthy subjects only) and detumescence (Det) and serum levels of GH determined. Patients: Thirty five (35) healthy males (mean age: 26 years) and 45 patients with erectile dysfunction (mean age: 52 years). Intervention: Blood withdrawal from cubital vein and penis. Main outcome measures: Tissue bath experiments using human erectile tissue, radioimmunometric measurement of GH. Results: ODQ and L-NOARG abolished the relaxation of the tissue induced by EFS, whereas amplitudes were increased by GH (1 nM - 100 nM). The attenuation of EFS-induced amplitudes by L-NOARG but not ODQ was, in part, reversed by GH. cGMP production induced by 10 nM GH was abolished in the presence of ODQ. Combing GH (10 nM) + L-NOARG (10 µM) maintained cGMP-production above baseline. In the healthy males, a marked increase in GH was registered during Tu (5.2 ± 8.2 to 9.5 ± 12.4). In the patients, GH levels were determined to be 7-fold lower than in the blood of the healthy males. Furthermore, the increase in systemic and cavernous GH levels from Fl to Tu was 5-fold weaker. Conclusion: Our data provide evidence that GH is of importance in the maintenance of male erectile function.