I’m not big on studies, due to their flawed/ corrupt nature, but I have seen a study where they compared fertility levels in guys using cyp, and guys using prop, at the same dosage per week, and the men on prop had pretty significantly higher sperm counts, and quality
I haven’t dug too deep into Natesto, or Jatenzo, but from my understanding, both preserve fertility better than longer ester preparations of test, like test cyp/ enanthate. I assume this is due to their very short half lives, and therefore less HPTA suppression
Proviron has been shown to actually improve fertility levels, in men with low sperm counts. Part of the reason it’s able to avoid being as suppressive, in regards to fertility, as other AAS, is most likely due to it’s short half life.
And my personal anecdote doesn’t confirm anything, but with my latest child, I switched from deca and test enanthate, to NPP and test prop, to attempt to make conceiving easier, and me and my fiance were able to conceive the first month we tried. This is me being on HRT for a little over a decade, as well as being on pretty significantly higher dosages than most guys using HRT. Now would we have conceived the first month trying if I stayed on deca and test enanthate, maybe. Impossible to say, obv. But from everything I’ve seen/ read over the years, I fully believe that test preparations with either no ester, or a very short ester, will result in less HPTA suppression than longer ester test preparations. Btw, for reference, I’ll be 38 this year, and my son is 4 months old as of today