SARMs will cause some suppression, but a lot of it also depends on the individual. Unfortunately, not a lot of or any actual human studies have been done on this issue. Right now we are relying heavily on individual experiences to evaluate short term and long-term effects of SARMs. From what I have found by people willing to share their blood work and other testing is that if used properly and cycled properly you should not have any issues, but I am not a medical professional in any way and I don't see medical professionals putting their license on the line by making those claims.
Any time you use SARMs, Steroids, or other PEDs you need to understand you are taking on some risk of things not going right. It is just up to you to research known side effects and benefits and decide for yourself if you are willing to accept the risk of the bad for the good benefits that come with it.