A number of skin and hair disorders can lead to eyebrow hair loss and sometimes it may be linked to systemic diseases like lupus. Specific skin and hair disorders that are most likely to lead to eyebrow thinning and hair loss have been discussed below but other conditions like psoriasis may also be involved if it occurs on the eyebrow or forehead. Eyebrow hair loss may occur in people on chemotherapy (cancer medication) and with radiation therapy to the head.
Thyroid Dysfunction: Since the thyroid gland regulates many body functions by releasing hormones, any disruption in its functioning can cause loss of hair, including eyebrow hair. If your thyroid is underactive, it could cause you to lose the outer third of your eyebrow. The only way to treat thyroid dysfunction is through medication. However, there’s still no guarantee that your eyebrow hair will grow back.
Furthermore, Penn dermatopathologists developed an even more advanced method called the HoVert technique for diagnosing hair loss and other disorders from a scalp biopsy. The technique uses a unique horizontal and vertical testing approach that provides a greater amount of information to the referring dermatologist than standard industry longitudinal scalp biopsies.
Try to include 'hair friendly' foods in your diet, such as Omega 3 rich salmon and walnuts; beat-carotene rich sweet potato, butternut squash, carrots, pumpkin and spinach (yes, dark green veggies are a good source of beta-carotene too); and foods like eggs (rich in biotin, B6, B12, selenium, zinc and copper), lentils (which are loaded with hair-healthy vitamins and minerals), chicken or turkey (which contain lots of protein, B vitamins and minerals), plus vitamin C-rich fruits and vegetables like blueberries, kiwi, strawberries and tomatoes.
Thyroid hormone receptors were detected in both dermal and epithelial compartments of the human pilosebaceous unit. T4 and T3 decrease the apoptosis of hair follicles and T4 prolongs the duration of anagen in vitro. Thyroidectomy delays initiation of anagen. Administration of thyroxine advances anagen, initiation of which is however delayed once toxic doses are given. Therefore, ratio of telogen to anagen hairs is increased in hypothyroidism as well as hyperthyroidism. Thus, the hair follicles are affected in thyroid disorders, and madarosis is caused due to disturbances in hair cell kinetics. Hypothyroidism is associated with generalized hair loss probably due to coarse, dull, and brittle hair with reduced diameter. The eyebrows and eyelashes may also be lost. Loss of lateral one-third of eyebrows known as Hertoghe sign is a characteristic sign of hypothyroidism. Some people also refer to it as Queen Anne's sign, after Anne of Denmark whose portrait with shortened eyebrows has been interpreted by some as indicative of the presence of goiter, even though such a fact has not been proved by any known sources of information. Madarosis may even be the presenting sign in hyperthyroidism. In hyperthyroidism, there is thinning with breaking off and shortening of hair. Madarosis can also occur in hypopituitarism, hypoparathyroidism, and hyperparathyroidism.