
If he's peeing AND pooing in the lounge, it's not likely to be linked to his hormones. Spraying is quite different from normal peeing and is directed up against vertical surfaces. Pooing can in some cases be territorial but my gut feeling is that he's either feeling stressed, or has become confused about appropriate surfaces to eliminate on.
How many litter trays do you have, and how many cats? The rule of thumb is one per cat and one extra, as some cats in multi-cat households can intimidate others to prevent them using certain trays. Or he may be stressed about one of the other cats - something you probably haven't even noticed as cats are very good at pretending nothing is happening, the only signs being elimination in the wrong place/s.
Where is the tray he uses the most, sited? If you've moved it recently he may be objecting to that. Have you changed brand of cat litter lately? That might also put him off using the tray.
I would exclude him from the lounge completely if you can, and give it a thorough deep clean with appropriate odour eliminators. Only let him back in once you are satisfied he is using his tray normally again elsewhere. The problem is that once cats start pooing and peeing on certain surfaces (such as carpet or upholstery) they can develop a preference for those surfaces, so you may need to restrict him to areas without any of these surfaces for a while to 'retrain' him.