Yes, hair transplant surgery can be an effective method for reducing the appearance of a large forehead. The suitability of hair transplant surgery to reduce the size of your forehead can depend on several factors, such as the thickness and quality of your donor hair, the extent of your hair loss, and the specific goals you have for the procedure. Age is another factor that can affect your suitability for the surgery, but it’s certainly the main factor, and you shouldn't be disqualified solely based on that. That being said, 19 is a little too young, and I would suggest waiting for a few more years before a transplant surgery to see if you may be prone to hair loss. You would need to consult with a qualified hair transplant specialist who will outline all the options and suggest the best technique or procedure most suitable and effective for your unique case. Take a look at this young patient of mine who got a forehead reduction through FUE surgery. It’s not for everyone, but it could be for you.