Rabbi Natan Slifkin writes:
What's the strangest segulah you've ever heard of? Last week, I picked up a book entitled To Fill The Earth: 277 Segulos and Advice on Fertility Issues, In Personal Consultation with Maran HaRav Chaim Kanievsky, Shlitah. Opening it at random, my eye fell upon the following segulah, in a chapter entitled "Segulos Pertaining To Food":"A dried pig's testicle, pulverized and ground up, will help a woman conceive. If the right testicle is used, a male child will be born; if the left testicle is used, a female child will be born (Segulos Yisrael, ma'areches os ayin, from the sefer Mar'eh Yeladim)."
Note that there is no kashrus problem here, for reasons that are too complex to get into right now.
All I can say is, as bad as this nonsense is, it's a helluva lot better than rabbis who convince desperate women they'll conceive a child – but only after the woman's womb is 'opened up' by having sex with the rabbi first. At least this kabbalistic segulah didn't make it into the book Slifkin bought.
As for the kashrut question, once the testicle is dried so much that it can be ground into a powder, it is considered to be "like wood" and therefore essentially becomes pareve. It is this same halakha that allowed the use of animal rennet and animal gelatin for hundreds and hundreds of years and treat them as pareve.
But what about the fact that the pig is inherently non-kosher and can't be eaten in any case? The halakhic answer to that is that medicines made from non-kosher ingredients are permitted to be taken if prescribed by a doctor (or a rabbi, sadly) unless there is an available medicine of equivalent or better efficacy. (And of course when it comes to medicines in pill form that are swallowed whole, even if they're made from non-kosher ingredients they can be consumed because swallowing something whole is not the normal way people eat, and because the pill has no beneficial taste.)