Thinning eyebrows is common in menopause, and the remaining hairs may grow longer, become coarser, or even change in color. The most common cause of hair and eyebrow loss in menopausal women is the decline in hormone levels associated with this stage of life.
Prostaglandins are hormone-like compounds influenced by estrogen and progesterone. As levels of these hormones drop during menopause, so do prostaglandin levels. Because prostaglandins help signal eyebrow growth, reduced levels can lead to thinning brows.