Possible role of human growth hormone in penile erection

Purpose: Treatment with recombinant human growth hormone in adult patients with growth hormone deficiency increases nitric oxide and cyclic guanosine monophosphate (cGMP). We examined the functional in vitro effects of recomb inant human growth hormone on tissue tension and cyclic nucleotide levels o f human corpus cavernosum and detected changes in growth hormone in the cav ernous and peripheral blood during different phases of penile erection. Materials and Methods: Relaxant responses of human corpus cavernosum were i nvestigated using the organ bath technique. Tissue levels of cGMP were dete rmined by a specific radioimmunoassay after dose dependent exposition of is olated human corpus cavernosum strips to recombinant human growth hormone. In 35 healthy potent volunteers blood samples were obtained simultaneously from the corpus cavernosum and cubital vein during different; functional co nditions of the penis, including flaccidity, tumescence, rigidity and detum escence. Penile erection was induced by audiovisual and tactile stimulation . Serum growth hormone was determined by an immunoradiometric assay. Results: Recombinant human growth hormone elicited dose dependent relaxatio n of human corpus cavernosum strips in vitro. The relaxing potency of recom binant human growth hormone was paralleled by its ability to elevate intrac ellular levels of cGMP. In vivo the peripheral growth hormone serum profile of the respective penile conditions did not significantly differ from thos e of cavernous serum. The main increase in growth hormone to greater than 9 0% was determined during developing penile tumescence,followed by a transie nt decrease afterward. Conclusions: These results suggest that penile erection may probably be ind uced by growth hormone through its cGMP stimulating activity on human corpu s cavernosum smooth muscle.