I had this problem several years ago.
As it happened I had to see a dermatologist about something else.
The consultant noticed the loss of frontal hair and eye brows.
He diagnosed Frontal Fybrosing Alopecia.
He prescribed a strong steroid lotion to be applied around the thinning hair area and a six months course of antibiotics.
I am beyond grateful to this wonderful, caring consultant (NHS)
because the treatment halted the hair loss. Now you would never know.
I do have an area on my forehead which is scar tissue, where the loss occurred, but the healthy growth above it conceales this.
Sometimes I see women who have this condition and have completely lost their hair from just above the forehead to the crown of the head.
If you suspect this could be what you have, please ask for a referral.
I was lucky. I hadn't asked, it was the kindness of the consultant who took the trouble to go above and beyond his remit on my behalf. I'm beyond grateful. 