My opinion is that anything that encourages or creates leg muscle growth, will increase your testosterone levels. Doing intervals and making bigger tears in the muscle to gain a higher amount of power/ftp will increase your testosterone levels as well. If you are doing such long rides and not nourishing your body properly, I could see how you would start to loose muscle/become emaciated and have your test levels decrease. Just my two cents, I am not a doctor and I do not have any reference material to site.