Ox can and will supress htpa. It also depends on the individual. I did 40 mg a day for 12 weeks and it shut me down, made my nuts hurt and diminish in size by the 6 week mark, Now, if that has nothing to do with HTPA, then I could be wrong, but I am willing to bet if you asked a the bros on this board who did an Anavar only cycle of any substance (40+mg a day) a majority of them will tell you that it will shut you down. Although anavar has a low incidence of side effects, you will be fooling yourself if you think that there are none. I did not get acne, no hair loss etc- but I did get shut down pretty hard.
In theory, homeostasis keeps nat test production leveled off. When you introduce a steady supply of outside test, or a test derivitave, or another similar compound into the body then the body senses that there is now a constant outside source, so it begins to slow or stop production. With Anavar, it has such a short half life that if it is taken in one dose it is out of the body in less than 24 hours, thus not being a steady supply of outside test. So, as a result the body does not shut down as hard. That is probobaly as clear as mud, but I am pretty sure that is why I shut down and some guy that took it all in the am might not.
C.