Most steroid users are eugonadal (testis, pituitary, and hypothalamus function fine) before they start their cycle, and their cycles usually are not enough of an insult to significantly damage the HPG axis. Thus, they are able to restimulate the HPG axis after a steroid cycle. It should be cautioned though that steroid abuse does cause insult to the HPG axis, and a number of steroid abusers will become hypogonadal at some point.
If you have been diagnosed with hypogonadism, your HPG axis is dysfunctional, and the PCT that steroid abusers use to restart the HPG axis will generally only temporarily restart it, until the stimulus (PCT) is removed.
It should also be noted that the NEJM article that showed successful "restarts" of hypgonadal men was able to bring half of the men with test levels of 20-100 ng/dL to levels around 300-400 ng/dL. The other half of men had their test levels raised, but the levels remained below 300 ng/dL.
Most men will find better relief of symptoms through a carefully designed TRT program, which at the present time needs to be utilized for life.