Does metformin treatment effect dihydrotestosterone (DHT) and the (male pattern) hair loss?

Yes metformin is known to cause hair loss.  I suggest you see an expert for treatment.  Best, Dr. Emer.

Fda doesnt advice metformin in hair loss treatments, we can not use that treatment with the knowledge we have so far.

Metformin does not cause hair loss, according to significant scientific research. Taking metformin for a long time may cause hair loss indirectly due to anaemia, according to a study conducted in 2016.Metformin treats diabetes type 2 and PCOS, both known causes of hair loss. In addition, it appears to lower testosterone, thus preventing male pattern baldness.

NO, one can't conclude that metformin has these effects on DHT unless that studies have been done. It would seem likely that it would lower DHT. Certainly metformin would not cause male balding as it's effects on insulin, IGF-1, and androgens are opposite to what potentially causes balding. Metformin improves insulin sensitivity, reduces obesity and lowers free and possibly total testosterone. 
Of course, studies have never been done, but one would hypothesize at least for an obese man, that metformin would help rather than hinder that process of slowing male balding. 
Metformin can cause hair loss....but that's very rare. The type of hair loss induced by metformin, although rare, is not of the male pattern balding type. 

Yes, Metformin has been reported to produce hair loss as does many drugs that are out there.  Check with your doctor about this side effect