The eyebrows are two-arched eminences of skin situated above the orbital regions.[3,4] The hairs of the eyebrows are short, thick. and stiff and are set obliquely. The diameter of eyebrow hair is normally thinner than scalp hair in Asians, and the scalp hair in thinner in Caucasians.[5] The eyebrows can be roughly divided into three parts. The medial third is usually below the orbital margin with the hairs in this region oriented vertically. The middle third lies along the orbital margin with hairs oriented obliquely or horizontally. The lateral third usually lies above the orbital margin.[3] Eyebrow hair normally tends to be less dense laterally than medially; thus, hair loss from any cause is apt to be more obvious in the lateral portion.[6]

When a woman is experiencing hair loss and has PCOS, spironolactone is often prescribed and it can be helpful but it’s important as well to address all these other issues when it comes to PCOS related hair loss. It’s also important to know that there is only a mild correlation of elevated testosterone on a blood test and hair loss. This is likely due to the hypersensitivity of the follicle to androgens in PCOS. Basically we get an exaggerated reaction from a smaller amount of testosterone.
Tames and Goldenring described a case of bilateral loss of eyebrows and eyelashes in a patient with AIDS-related complex who had smoked crack cocaine. This has been attributed to hot vapors during the process of smoking, and which therefore caused singeing of the brows and lashes. There was a complete reversal once the patient abstained from cocaine.[93]
Contact dermatitis causes skin inflammation and when severe it can affect the hair follicles as well. It can either be due to some irritant making contact with the skin of the eyebrows or due to a substance to which a person has an allergy. This gives rise to the two types of contact dermatitis – irritant contact dermatitis or allergic contact dermatitis. Substances that could cause contact dermatitis at the eyebrow includes eye makeup including eyebrow pencils, hair removal creams and waxes, other cosmetics, hair dyes and scalp hair styling products.
Alopecia areata is a chronic autoimmune disease in which the immune system erroneously attacks the hair follicles, causing inflammation and temporary hair loss. Any hair-bearing skin site can be affected by alopecia areata, including the eyebrows. Treatment commonly involves corticosteroid injections into the site of eyebrow loss. Eyebrow hairs usually grow back, but may be a different color or texture than the lost hairs.
To prove the fact that this does not happen on your scalp alone, Everyday Health notes, “too much thyroid hormone, the hair on your head can become fine, with thinning hair all over the scalp. When there is too little of this hormone, there can be hair loss, not just on the scalp, but also anywhere on the body”. This proves patients with underactive thyroid (low thyroid) can have their eyelashes and eyebrows falling off.
Thyroid hormone receptors were detected in both dermal and epithelial compartments of the human pilosebaceous unit.[48] T4 and T3 decrease the apoptosis of hair follicles and T4 prolongs the duration of anagen in vitro.[49] 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.[50] 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.[51] The eyebrows and eyelashes may also be lost. Loss of lateral one-third of eyebrows known as Hertoghe sign[38] is a characteristic sign of hypothyroidism.[52] Some people also refer to it as Queen Anne's sign,[53] 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.[21] In hyperthyroidism, there is thinning with breaking off and shortening of hair.[54] Madarosis can also occur in hypopituitarism, hypoparathyroidism,[21] and hyperparathyroidism.[55]
Protein: When the body does not get enough protein, it rations the protein it does get. One way the body can ration protein is to shut down hair growth. About 2 to 3 months after a person does not eat enough protein, you can see the hair loss. Eating more protein will stop the hair loss. Meats, eggs, and fish are good sources of protein. Vegetarians can get more protein by adding nuts, seeds, and beans to their diet.
Unfortunately, there’s no magic solution, pill or product that will correct hair loss entirely. But if you think of your hormones as a cast of characters, knowing which ones are leading the show and which ones are only playing a supporting role can help you get to the bottom of the issue. If you haven’t already, take my free hormone quiz – it can help you determine what tests you may want to request from your doctor and which lifestyle or dietary changes may benefit you most. In the meantime, manage your stress levels and get enough sleep. This will help with general hormone balance and can protect your precious locks from any further damage.
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