A fellow sufferer here, my thin hair sides aren't as worse as yours though. I also have some thinning on behind the ears and in the nap area. As for the traditional male pattern baldness, my hair loss is only limited to the temples (~NW2).
I've been on finasteride for 4 months and recently (~3 weeks) started minoxidil and I am applying it ONLY on the temples, the sides and the nap line in a hope to thicken at least the sides. As far as titles concern, retrograde alopecia seems indeed ambiguous and I have YET to find anyone speaking about its cause over the entire web. The cause is unknown, some place it on DHT (an extension of male pattern baldness), some place it under totally different conditions.
As for myself, I've been suffering from intense stress since 2008, I am hoping that my irregular thin areas are caused by some kind of a chronic Telogen Effluvium. All in all, I am looking forward for them to respond to both finasteride and minoxidil. Good luck.