Among other things, in a drug that is used to treat BPH (benign prostatic hyperplasia — a non-cancerous enlargement of the prostate), and male pattern hair loss. It's also sometimes used as a hormone replacement in FtM transgender individuals.

It's widely rumored that President Trump uses it for hair loss, which I suspect is part of why this article was shared, and is being upvoted; this side effect wasn't exactly unknown before this study...

they are used for treating prostrate enlargement as well as hair loss in men, among other things..

https://en.wikipedia.org/wiki/Finasteride https://en.wikipedia.org/wiki/Dutasteride

But I don't think that this side-effect was unknown. ED / sexual dysfunction is a documented side effect for both the drugs in a significant percentage of the patient population.

I think this study is exploring "persistent" ED, which is less known. ED is a documented side effect, but this shows that some men continue to experience ED even after they stop taking the drug.

The linked Wikipedia article cites references to persistent ED and diminished libido common enough to warrant changing the labeling on the drug in 2014.

So, yes, this study is exploring that side effect, but it's inaccurate to call it "less known".

EDIT: fixed some word salad phrasing.

The common brand names are Propecia and Proscar.

Propecia and Proscar are finasteride. The common brand for dutasteride is Avodart.

They are both drugs to treat enlarged prostate (benign prostatic hyperplasia)