Ernie:
There's a huge variation between individulas in what is
normalNormal saline flush. If your eyebrows are thinner than most, that doesn't represent a disease in an otherwise healthy individual like you, just a variant of
normalNormal saline flush. (Some men are embarrassed by having too much eyebrow hair, "beetling" eyebrows.)
WomenWomen's way with this complaint would use eyebrow pencil. In our culture men don't do that. Any hair products designed to make hair look thicker (by coating it with protein) might be worth a try on the eyebrows. For specific product recommendations, I suggest asking a hairdresser.
Best.
Dr. R