I’ve tracked down two studies, both of which trialled men with no obvious somatic cause for their dysfunction. The studies reported significant increase in npt for the men taking naltrexone (but not the placebo).
The first (University of Rome) trial reported that 11 of 15 patients improved their sexual performance too, and that two months later, five were still improved. The second (University of Bonn) trial again reported much increased npt, but implied little or no improvement in sexual function.
No increase in LH or testosterone was found in either trial, suggesting that the positive effect of the drug on sexual behaviour was exerted at a central level. There were no significant side effects.
The Bonn trial reflects my general experiences with my own ‘experiments’: increases in npt are easy, but translating that to better sexual function is not.
The Rome trial was a little vague about the extent of improvements in erectile function
But naltrexone is reasonably cheap (about £10 a week) and I might give it a try.