
Medicine cannot directly affect genes (I believe. Didn't cite my sources).

I'd like to think "Wolf in sheep's clothing", so the other way around: he's actually a wolf with rare recessive goat genes that make him kinda camouflage, or appear as prey (a sheep or goat)
Well the heat medicine could affect his genes. I learned there's medicine that can cause expression of certain genes (i.e sickle cell anemia meds that activate dormant fetal genes to produce normal blood cells). So maybe there's an adverse reaction in the heat medicine that makes his dormant wolf genes start expressing over the goat ones.
Or just being near his own species during heat triggers it. Either way, we are so deep in this guys. We got it all figured out. And the next chapter probably won't come till 2020 XD T_T
I think that the goat wolf hybrid works something like this:
Sex drive, ON= eyes changing
Sex drive, over 9000= even more of a change
This could be explained by instincts, since herbivores are generally peaceful, but there could be some kind of recessive gene to make a creature more aggressive. In order to channel that aggressiveness, he has to change into a more aggressive animal, or more specifically, a predator. In this case, it just so happens to be a wolf. Hence, the goat-wolf.
(BTW, a recessive gene for those who don’t know is a gene whose effects only show up if there is two of them. In order to have this effect, both parents had to have had this gene, snd BOTH had to pass it down. However, since I’m going to assume that they had a dominant gene as well because they probably aren’t getting chased by government officials and scientists as shown through the small flashbacks here and there and wolf-san being friends with goat-san, both having a seemingly normal childhoods, the effects didn’t show, although the parents still had the recessive gene. However, goat-san happened to inherit ONLY that recessive gene from his parents, meaning that the effects would show.)
And then it turns out that wolf-san is simply hallucinating and all the speculation is going to waste.
But that would be bad writing so I don’t think that will happen.
On a side note, isn’t wolf-san so precious. Like, loOk aT tHAt tAiL. And the nose rub. And when he put the rabbit ears on. hOLy ShIEt.
Please wait as I flop around on my bed like a fish out of water and scream silently into my pillow.
Thank you for listening to my TED talk.