Slight hair thinning, 18M -- I'm not sure I want to start finasteride so soon?

So I’ve experience a mild thinning in the front part of my hair/head (Norwood 0 thankfully – for now.) but noticed my scalp being pretty visible under light with what I believe to be a rather sudden loss in density, so I went to the derm.

The dermatologist I had was very helpful and ordered me to have labs done as well, and I’ll be checking up with them in a few months.

The derm said it could be a number of things, possibly telogen effluvium, micronutrient or vitamin deficiency, etc.

They prescribed me a ketoconazole shampoo and clobetasol (due to scaling), but also this solution with minoxidil, finasteride and tretinoin. The minoxidil, according to the derm, is to kickstart any thinned hairs that may have gotten smaller due to deficiencies and whatnot.

I don’t object because I know I’ll keep my hairs that I had before once I’ve stopped, etc.

The thing is, I’m a bit apprehensive to start finasteride so soon since they’re not sure what is causing any loss just yet, not necessarily for the sides but for possible systemic absorption, also since I also still want new facial hair to develop.

I know that’s a bit strange, but besides my own minor worry, I want to know what other people think as well, if it’s potentially a bit premature to start fin.

Starting fin at your age can help if it’s AGA, but if you’re unsure about systemic effects, focusing on min and addressing potential vitamin deficiencies is a good start. Minoxidil is effective for regrowth, and tretinoin will aid its absorption. You can revisit fin or a topical form if needed later.

Thanks for the reply.
This is probably what I will do, then.