Run a solid PCT, I did 1, 4, and Epi Andro for 8 weeks over spring time, used Sup3r PCT, Nolva, Super Rhanderol, and Sustain Alpha plus ate slightly above maintenance cals and seemed to have kept most of my gains.
To answer your question you would lose gains because your natural test levels will be bottomed out, your E levels will rebound, and your cortisol will spike after cycle.
A general thing people do in PCT is run a OTC all in one PCT product, a natty test booster (that's what Sustain Alpha does) and some kind of natty anabolics.
After my next cycle I will be using BPS Sustain Alpha&Androcrine (transdermal Laxogenin), OL EP1C Unleashed (Epicat) and Sparta Trojan (OTC PCT) along with my SERM. Probably sounds like a lot of $$$ but it's worth it IMO to keep and solidify the gains you made on cycle.
Hope this helps.