Frontal thinning is a side-effect of Androgenetic Alopecia (male pattern baldness) not Finasteride.
While some men will claim Finasteride sped up their hairloss process, this has no bases in science nor do any of these men provide clear photographic evidence.
The two most likely scenarios are:
#1. You are a non-responder to Finasteride either in general or in certain areas.
How?
Finasteride inhibits the type II 5ar enzyme thus reduces DHT levels by preventing testosterone from being converted into DHT. However, Finasteride does not inhibit 100% of DHT nor is DHT the only androgen.
So, if your hair in general is still sensitive enough to the remaining androgens or if certain areas of your scalp are more sensitive to androgens you may see a continuing of the balding process.
Furthermore, underlying medical conditions such as a thyroid problem or Telogen Effluvium can exaggerate and accelerate the balding process.
#2. When you start on Finasteride there has been some people who have suggested that hairs near the telogen phase (resting phase) are pushed into telogen prematurely. This causes a shed which can make the hair thinner in the affected areas.
This is further exaggerated as men with male pattern baldness usually have a higher telogen to anagen ratio.
Shed hair takes 3 months before it starts growing again. If the hair was almost already "dead" you may not recover it. However, such hair would have been lost soon anyhow so it really doesnt matter. Hair that could be saved should grow back the same or even stronger/thicker.
Long story short, Finasteride doesnt cause thinning of your hair. male pattern baldness causes thinning of your hair!
Good luck and consider giving Finasteride not only a solid 6 months to one-year before drawing any conclusions but also take monthly pics with a high quality camera (preferably a digital one).
