For other women, the problem with estrogen dominance is that they’re also experiencing lower levels of progesterone relative to estrogen—and progesterone helps protect hair follicles from the hair-thinning effects of testosterone, DHT, and estrogen. Evidence suggests that progesterone may act as an aromatase inhibitor and other research suggests that the genes involved in aromatase activity are implicated in female hair loss.
If you’ve overplucked your brows too many times, you may have caused trauma to the follicles in the meantime, signalling not only those hairs you plucked to stop growing back, but also the hairs in surrounding areas. The good news: If the hair follicles aren’t dead, they can possibly be shaken from their resting state with a good brow enhancer. (like WINK  yes of course, we have to say it). There’s no sure bets, but it’s worth a try–plus Wink has a money-back guarantee!
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]