Eyebrow hair loss, no other hair loss - young male

I have been experiencing eyebrow hair loss for about 1-2 years. I am a 27 year old male with no other hairloss. My eyebrow hairs fall out very easily and have a white bulb at the end. But, they always grow back fast. It seems as if the hairs are extremely weak. Thyroid and blood test came back healthy. No itching or redness on my face/eyebrows. The dermatologist could only prescribe ketoconazole shampoo to put on my scalp and on my eyebrows. This had no effect.