Steroid Fatigue is a common catchphrase these days, and refers to another important function of estrogen in both the female and male body, its ability to promote wakefulness and a mentally alert state.
Given the steroids that have aromatase inhibitors, bodybuilders today are noticing at some points more fatigue and extreme estrogen suppression than they had in the past.
Under these conditions, the athlete,though on a productive cycle of drugs or steroids as you can name them, may not be able to maximize his or hers gains due to an inability to train at full vigor. This effect is also called sometimes steroid lethargy and sometimes it is followed by a sensation of fatigue and the reason is that estrogen plays an important supporting role in the activity of serotonin.
Serotonin is one of the body`s principal neurotransmitters, vital to mental alertness and the sleep/ wake cycle. Interference with this neurotransmitter by steroids or anything else is also associated with chronic fatigue syndrome so from that you can see how vital it is to fatigue (the serotonin).
Although not everyone that is using steroids notices this problem with fatigue when estrogen levels are low, for those that do, a little testosterone or estrogen can go a long way in correcting this.
The use of strictly non-aromatizable steroids sometimes causes this effect of fatigue as well, likely due to the suppression of natural testosterone production cutting of the main substrate used by the male body to make estrogen.