When people talk about factors related to erectile function, Nitric Oxide often comes up. However, Nitric Oxide has a less famous accomplice, Hydrogen Sulfide. Hydrogen Sulfide production is modulated by testosterone, and uses the amino acids cysteine or methionine as building blocks.
I view Hydrogen Sulfide as one of the four key elements of erectile function, alongside DHT, Nitric Oxide and Dopamine.
In vitro study: Testosterone increases production of Hydrogen Sulfide in rat aortas
https://www.ncbi.nlm.nih.gov/pubmed/18511180
The study involved exposing rat aortas to testosterone, which resulted in the cells producing hydrogen sulfide. The effect seemed to be modulated by the cystathionine gamma lyase (CSE) enzyme which converts the amino acid cysteine into hydrogen sulfide, given that when CSE inhibitors (PGG) propargylglycine and BCA were used, the production of H2S significantly reduced.
In vitro study: The impact of Testosterone on Hydrogen Sulfide by be modulated by the androgen receptor (NR3C4)
https://www.ncbi.nlm.nih.gov/pubmed/24750035
http://pubmedcentralcanada.ca/pmcc/articles/PMC4369260/pdf/bph0172-1505.pdf
Testosterone induces rat aortas to produce H2S. This study found that the effect was suppressed if the aortas were pretreated with androgen receptor antagonist nilutamide. As in the previous study, CSE inhibitor propargylglycine also suppressed the effect. Neither progesterone nor estradiol (E2) induced H2S release - suggesting this is a testosterone specific effect. The study also found that CSE is physically associated with the the androgen receptor. Finally, the study also found that H2S blood from healthy human male volunteers were higher than those in females.
NOTE: It's perhaps important to remember that nicotinamide can boost androgen receptor expression.
Enzymes that produce H2S, CSE and CBS, require Vitamin B-6 as a co-factor
https://www.ncbi.nlm.nih.gov/pubmed/15280798
Resveratrol stimulates Hydrogen Sulfide (H2S) in rat penises
http://www.jsm.jsexmed.org/article/S1743-6095(15)34433-7/fulltext
In the mouse brain, SAMe is a H2S regulator
https://www.ncbi.nlm.nih.gov/pubmed/12358731
http://www.jsm.jsexmed.org/article/S1743-6095(15)33601-8/pdf
H2S may be involved in pain processing
https://www.ncbi.nlm.nih.gov/pubmed/23830907
http://www.nature.com/nrurol/journal/v8/n5/full/nrurol.2011.45.html