Yup.
You're treating the follicles, not the hair that you shaved off.
Get on Propecia, 1mg daily. If you experience side effects, depending on the severity, try and see them through.. otherwise you can stop taking Propecia and you will be fine again.
Get minoxidil, depending on the stage of hairloss.. otherwise you will want to use Propecia for a year first, to judge if it has worked for you.. before adding minoxidil to your regimine.
Get Nizoral 1% shampoo from the pharmacy or grocery store.
Those are called "The Big 3" around these parts.. they're the most important to help maintain hair (Propecia), regrow hair (Minoxidil), and keep inflammation/itching to a minimal, for nice hair growth environment (Nizoral 1% shampoo, 2 - 3x weekly.. let it sit for 5 minutes or so each time you use it). Nizoral also has added anti-androgen properties, which can't be a bad thing in the fight against male pattern baldness.