Telogen effluvium, a type of scalp hair loss characterized by hair shedding, may affect the eyebrows as well. It can be caused by any emotional or physiological stress, for example acute or chronic illnesses, hormonal changes, nutritional deficiencies, and medications that alter the normal hair cycle and cause the hair the enter the telogen phase prematurely.  

Dutasteride is a 5-alpha-reductase inhibitor that binds both types I and II enzymes. Compared with finasteride, its inhibition of type II enzymes is three times more potent; its inhibition of type I enzymes is 100 times more potent (Clark et al., 2004). Dutasteride is not approved for the treatment of FPHL by the FDA, and ongoing studies on the efficacy of the inhibitor are promising but largely focus on male patients (Gupta and Charrette, 2014, Olsen et al., 2006). A study of women after 3 years of therapy showed that dutasteride may be more effective than finasteride in women under 50 years of age as measured by hair thickness (not hair density) at the center and vertex scalp (Boersma et al., 2014). One case report of a 46-year-old female with FPHL showed some response after 6 months of treatment with a dose of 0.5-mg dutasteride daily despite a minimal response to treatment with finasteride and minoxidil (Olszewska and Rudnicka, 2005). Data with regard to the treatment side effects in women is extremely limited. Dutasteride is classified as pregnancy category X because of teratogenicity and should have the same theoretical risk of breast cancer as mentioned in relation to finasteride (Kelly et al., 2016).
When men have hereditary hair loss, they often get a receding hairline. Many men see bald patches, especially on the top of the head. Women, on the other hand, tend to keep their hairline. They see noticeably thinning hair. The first sign of hair loss for many women is a widening part. In rare cases, men see noticeably thinning hair. And in rare cases, women can see a receding hairline or bald patches. The reasons for this are unknown.
Insulin regulation is also a big factor in hair health, as an imbalance can lead to various hormonal effects. Insulin helps to regulate blood sugar levels, which effects fat storage and hormone balance. Fat storage and hormone balance play a role in hair growth because fat storages will secrete excess estrogen in the body, and can desensitize hormone signals.  
It is perfectly normal for people to shed 50 to 100 hairs per day. This generally doesn't cause noticeable thinning of scalp hair because new hair is growing in at the same time that hair is shedding. However, hair loss occurs when this hair growth cycle and shedding is disrupted or when the hair follicle becomes destroyed and replaced with scar tissue. Female pattern hair loss (androgenetic alopecia) is the most common form of hair loss in women. This occurs gradually and is caused by genetics (from either side of the family), age, and the action of a specific male hormone, dihydrotestosterone (DHT). This hormone is found in lesser amounts in women and it preys on the hair follicles, preventing them from receiving vital nutrients for proper hair follicle growth, leading to the hairs shrinking, and resulting in a shorter lifespan. Interestingly, DHT does not need to be elevated to generate hair loss. Estrogen, when lowered as commonly seen in menopause, creates a change in the ratio of male to female hormones, giving an edge to these male hormones. Compounded with the sensitivity of DHT to the hair follicles, heredity can affect the age at which a woman begins to lose her hair, as well as the rate of hair loss and the extent of baldness.  

Sara Gottfried, MD is the New York Times bestselling author of the new book, Younger: A Breakthrough Program to Reset Your Genes, Reverse Aging, and Turn Back the Clock 10 Years. Her previous New York Times bestsellers are The Hormone Cure and The Hormone Reset Diet. After graduating from Harvard Medical School and MIT, Dr. Gottfried completed her residency at the University of California at San Francisco. She is a board-certified gynecologist who teaches natural hormone balancing in her novel online programs so that women can lose weight, detoxify, and slow down aging. Dr. Gottfried lives in Berkeley, CA with her husband and two daughters.
Here is one small European study which looked at 20 pre-menopausal women with female pattern hair loss to check their serum levels of estradiol, free and total testosterone, SHBG, LH, FSH, and DHEAS. These levels were compared to those of a control group without hair loss. Estradiol is one of the three naturally occurring forms of estrogen found in the body.
Another reason that you have thinning eyebrows might be low thyroid (which is called hypothyroidism. The thyroid gland controls the rate of use of energy sources, protein synthesis by producing thyroid hormones. I the thyroid gland does not produce enough hormones, you might feel tired, freeze in the cold, gain weight or lose your hair. The most common cause of hypothyroidism is iodine deficiency.
Reproductive hormone changes can also play a part, and dermatologists believe the same factors that cause hair loss from the scalp, a common problem for women as they age, may contribute to thinning brows. Nanette Santoro, M.D., ob/gyn and professor of reproductive endocrinology at the University of Colorado at Denver, says, “Abrupt hormone changes can cause sudden hair loss (telogen effluvium) that recovers over about six months' time. It happens postpartum to many women and can happen at menopause.”
This is an autoimmune disorder that is also known as “spot baldness” and can result in hair loss ranging from just one location (alopecia areata monolocularis) to the entire scalp (alopecia totalis), or to every hair on the entire body (Alopecia areata universalis). Although it is thought to be caused by hair follicles becoming dormant, what triggers alopecia areata is not exactly known. In most cases, the condition corrects itself.
Traumas such as major surgery, poisoning and severe stress may cause a hair loss condition known as telogen effluvium, in which a large number of hairs enter the resting phase at the same time, causing shedding and subsequent thinning hair in men and women alike. The condition also presents as a side effect of chemotherapy. While targeting dividing cancer cells, this treatment also affects hair’s growth phase, with the result that almost 90% of hairs fall out soon after chemotherapy starts.
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.
It is known that during pregnancy, because of an increased level of estrogen, there is a tremendous growth of new hair. However, during menopause it is noticeable that the reduced level of estrogen hormone tends to cause hair loss. When the estrogen hormone levels tend to drop, the hair follicles fall under the influence of the male sex hormone or the testosterone, which cause the shortening of the growth phase of hair. Subsequently there is a noticeable hair loss. This hair loss caused due to the drop down of estrogen levels may cause patchy hair loss or complete baldness.
If you’ve undergone chemotherapy recently, you know the effects that it has on your hair, including your brows and lashes. First of all, I want to point you to this awesome resource by FairyHairs (click here), that shows in intervals, with pictures, what you can expect with regrowing your hair after chemo (Thank you, Jenny Mealy!). The article also includes ways to regrow your hair after chemo.
Check for hypothyroidism. If you also notice unexplained weight gain, chronic fatigue, feeling depressed, or feeling colder than usual in low temperatures, your thyroid gland may not be producing enough hormones. You may also notice your periods getting heavier or becoming sporadic. Hypothyroidism is most common in women, especially over age 50, and it can be treated with a synthetic hormone.[31]
Hypothyroidism, or an underactive thyroid gland, adversely affects scalp and body hair growth. Thinning of the eyebrows can be a late sign of hypothyroidism. Other symptoms of hypothyroidism include chronic fatigue, weakness, constipation, weight gain and skin dryness. Treatment of hypothyroidism with thyroid hormone replacement medication typically leads to regrowth of lost eyebrow hair.
This is most commonly found in women wearing ponytails, tight braids or any hairstyles that typically pull on hair with excessive force. In addition, rigorous brushing, heat styling and rough scalp massage can damage the cuticle, the hard outer casing of the hair. This causes individual strands to become weak and break off, reducing overall hair volume.
Take extra care in looking after your hair. Use a gentle, nourishing shampoo (we love Bumble and Bumble Gentle Shampoo) to promote good condition and prevent breakage. Try using a silk or satin pillowcase. Avoid harsh styling products and techniques that apply heat to the hair (blow drying, curling irons etc) as these can cause more damage to fragile hair.
Over Plucking: I know the temptation of tweezing your eyebrows when you don’t want to endure the pain of threading. But when you pluck your eyebrow hair, you’re pulling it out from the follicle and essentially damaging it. And repeatedly plucking your hair eyebrow hair can permanently damage your follicles over time and prevent them from producing new hair.
Like with low thyroid, there can be a myriad of imbalances at play with PCOS related hair loss making it a complex issue that’s often written off as merely high testosterone. While androgen excess and hypersensitivity of the hair follicles to these hormones are part of the issue, these are other contributing factors to PCOS related hair loss as well:
Yes. If you wear pigtails or cornrows or use tight hair rollers, the pull on your hair can cause a type of hair loss called traction alopecia (say: al-oh-pee-sha). If the pulling is stopped before scarring of the scalp develops, your hair will grow back normally. However, scarring can cause permanent hair loss. Hot oil hair treatments or chemicals used in permanents (also called “perms”) may cause inflammation (swelling) of the hair follicle, which can result in scarring and hair loss. 

Menopause is a natural biological process that all women experience at some point in their lives. During this time, the body goes through numerous physical changes as it adjusts to fluctuating hormone levels. Many women have unpleasant symptoms during menopause, including hot flashes, mood swings, and insomnia. Hair loss is another common occurrence.
For now, therapies include cortisone injections directly into the bald patches; topical cortisone; Minoxidil — known to many people under the brand name Rogaine; and anthralin cream. A less-widely available option is topical immunotherapy: certain chemicals applied to the scalp can trigger an allergic rash, which alters the immune response, NAAF notes.
Surgeries, severe illnesses and emotional stress can cause hair loss. The body simply shuts down production of hair during periods of stress since it is not necessary for survival and instead devotes its energies toward repairing vital body structures. In many cases there is a three month delay between the actual event and the onset of hair loss. Furthermore, there may be another three month delay prior to the return of noticeable hair regrowth. This then means that the total hair loss and regrowth cycle can last 6 months or possibly longer when induced by physical or emotional stress. There are some health conditions which may go undetected that can contribute to hair loss. These include anemia or low blood count and thyroid abnormalities. Both of these conditions can be detected by a simple, inexpensive blood test.
Scurf refers to the scales and greasy crusts that accumulate along the hair shaft and indicates the presence of seborrhea.[26,27] Collarettes are composed of hard fibrinous scales[25,28] surrounding each individual eyelash. They travel upward along with the growth of the lashes and are indicative of staphylococcal infection. Sleeves or cylindrical dandruff comprise scales that form a cuff around the lash root and are connected with it, in contrast to greasy scales which are not connected to the lash root.[29] Sleeves indicate infestation with Demodex folliculorum.

Hair loss is something that everyone experiences sooner or later, but some get it earlier than others. Losing hair prematurely can be traumatic. Because of that, there is an infinite number of products that claim to cure and reverse the problem. But what if you could find out the likelihood that you will experience hair loss so that you could prevent it before the symptoms even showed? Researchers in the United Kingdom have reportedly found a way to predict who is at risk.
Giorgos Tsetis: There are really two industries at work here that have to be separated. First, there's the drugs, the pharma, which is the FDA world. Then, you have the naturals, the formulas, and the actual supplements industry. The supplement industry is really not properly regulated in this country. More surprisingly, starting a supplement company is very easy. That's why you see all of these supplements popping up, and the FDA doesn't even have the capacity to monitor them all and make sure people are able to substantiate proper claims. As a supplement manufacturer, all you have to do is create your products in a FDA approved facility, and there thousands of them in the United States. That means anyone can put a formula together and get away with claims until they get challenged by consumers or competitors. When you step into these factories, you see it's messy. You're not talking about state-of-the-art factories where people are doing the work. It's really scary. 

Most of us look at the eyebrows as a patch of hair that has an aesthetic purpose and it is often shaped for cosmetic purposes. Although the exact purpose of the eyebrows is not conclusively understood, it is believed to be prevent water or sweat from falling on to the eyes itself. For most people its function is of little concern compared to its cosmetic purpose. As with hair anywhere on the body, eyebrow hair and the follicles from where it arises can be prone to the same diseases and disorders which may lead to hair loss..
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