The best way to think of the way hair grows is to picture a garden. How well it grows is completely a result of what is happening “underground.”
“Like a garden, a normal hair cycle should lead to a product, which is the hair,” says Wendy Roberts, MD, a dermatologist in Rancho Mirage, CA. “Growth cycles are important because when they go awry, that is one of the reasons we have hair loss.”
And things that interfere with the cycle -- like medication, illness, infections, or chemicals -- have the potential to stop hair from being formed properly.
"It’s a very dynamic place and anything that can get the cycle off can cause hair loss,” Roberts says.
Although hair loss may seem like a more prominent problem in people assigned male at birth, you may be nearly as likely to lose, or have thinning, hair if you're assigned female at birth. Most women notice it in their 50s or 60s, but it can happen at any age and for a variety of reasons.
Taking hormones can change hair growth for anyone. Researchers are looking into how it affects people who are transgender or nonbinary, specifically. Transgender people don't identify with the sex they were assigned at birth. Nonbinary means that the person doesn't identify as male or female, and may identify as a combination of genders. A person can identify as both.
Way to Grow
Hair grows in three different cycles: anagen, catagen, and telogen. About 90% of the hair on the head is in the anagen, or growth phase, which lasts anywhere from 2 to 8 years. The catagen, or transition phase, typically lasts 2-3 weeks, during which the hair follicle shrinks. During the telogen cycle, which lasts around 2 to 4, the hair rests.
An overwhelming majority of the time the hair is on the scalp, it is growing. Only about 10% of the strands are in transition or resting at any time. Hair grows about 6 inches a year for most people.
At a Loss
Most people lose anywhere from 50 to 100 strands of hair each day, according to the American Academy of Dermatology. But 1 out of 3 women shed more than that. Lots of things can be responsible, including hormones, medication, stress, and even your styling habits. On the days when hair is washed, people can lose up to 250 strands, Roberts said. But don’t avoid washing in an attempt to keep the hair, as it will fall out eventually, anyway.
For those who don’t plan on counting their hair every day, there are ways to know when hair is thinning or being lost at a higher rate. Roberts says that women will see a difference. When waking up in the morning, there may be an usually large amount on your pillow. When you comb your hair (especially without tugging, which can pull the hair out), more than normal will be left in the comb.
There are also other visual cues that women can look for over time. Although men’s hair tends to recede from the forehead or the crown of the head, women tend to notice thinning on the top third to one half of the scalp. Sometimes their frontal line stays intact, says Nicole Rogers, MD, of Old Metairie Dermatology in Metairie, LA. Women may see a part that is gradually becoming wider or see more of their scalp than normal when their hair is pulled back.
Female Pattern Baldness
Another way to diagnose the problem is by looking and listening, Rogers says. She asks what a patient’s mother, aunts, or grandmothers look like -- if they have similar or greater amounts of hair loss. Using magnification on the scalp can show if the follicles vary in size, with some thick and others thin. These are two telltale signs of female pattern hair loss, also called androgenetic alopecia. (That term is also known as male pattern baldness, which affects specific areas instead of the whole head in people assigned male at birth).
This is a hereditary condition that affects about 30 million American women, according to the America Academy of Dermatology, and is the most common kind of hair loss Rogers sees in her practice. She says it happens to about 50% of women. Although it mostly occurs in the late 50s or 60s, it can happen at any time, even during teenage years, Rogers says.
Typically, each time a normal hair follicle is shed, it is replaced by hair that is equal in size. But in women with female pattern hair loss, the new hair is finer and thinner -- a more miniaturized version of itself, Rogers says. The hair follicles are shrinking and eventually they quit growing.
In men, the hair tends to thin out at the temples and can make them go bald. In women, it usually starts at the top of the head or at the part. It can look like a Christmas tree with thinned-out branches. You might hear it called female pattern baldness. But women rarely lose all their hair. Instead, their hairs tend to get sparse so you can see their scalps.
Illnesses That Cause Hair Loss in Women
If hair follicles are uniform in size, or if the hair loss is sudden, it is likely to be caused by something other than heredity, like a medical condition, Rogers says.
There is a wide range of conditions that can bring on hair loss, with some of the most common being pregnancy, thyroid disorders, and anemia. Others include autoimmune diseases, polycystic ovary syndrome (PCOS), and skin conditions such as psoriasis and seborrheic dermatitis, Rogers says.
Though there has been a link between menopause and hair loss, Roberts says she doesn’t think there is a direct correlation. It could be that menopause and hair loss just occur at the same age.
Other reasons for hair loss include extreme stress, physical trauma like surgery or intense illness, dramatic weight loss over a short period of time, and taking too much vitamin A, Roberts says. And hair loss can occur a couple of weeks to 6 months after any of these experiences.
“Someone can have surgery and be just fine and then 2 weeks later their hair starts falling out,” Roberts says. “It can be very scary when it starts falling out in big clumps.”
Other medical conditions that could lead to hair loss include:
- Ringworm, which can spread from person to person and can cause balding
- Infections or high fever
- Radiation and chemotherapy for cancer
- Autoimmune disease called alopecia areata. It makes your body attack your hair and leave round, bald patches.
- Scarring alopecia. This more often affects African-American women. Hair starts to fall out from the middle of the scalp and fans out, leaving parts of the scalp smooth and shiny.
- Birth control pills, blood thinners, and some steroids
Easy Does It
One other way to thin hair is self-inflicted: Hairstyles like cornrows or too-tight braids can cause hair loss called traction alopecia.
Other styling habits that can lead to problems include:
- High heat from a blow dryer or flat iron
- Harsh chemicals from bleach, perms, or other products
- Tightly pulled hair from clips, bands, or pins
- Over-shampooing or brushing and combing too much, especially when your hair is wet
All of the things women do to manipulate their hair -- dyes, chemical treatments, bad brushes, blow dryers, and flat irons -- can result in damage and breakage, Roberts says. This includes brushing too much and towel drying aggressively when the hair is wet. See how to spot the signs of traction alopecia before it becomes permanent.
Luckily, for most of these issues, the hair grows back or the loss can be reversed with medical treatments. But it is important to see a dermatologist if there seems to be something wrong because the sooner treatment is started, the better the chances are for improving your growing season. Learn more about how to reverse traction alopecia.
Hair Loss in Transgender and Nonbinary People
Anyone can experience androgenetic alopecia. These hair changes can make it hard to maintain how you want to look, especially if you are transgender or nonbinary. You may want to shift where hair grows (or doesn't) to show your affirmed gender. It can be distressing when hair loss patterns don't align with your affirmed gender. Taking hormones can change hair growth all over your body. If you're a transgender man, masculinizing hormone therapy (taking testosterone) may cause androgenetic alopecia. Some transgender women taking feminizing hormones like estrogen or antiandrogens experience hair growth on their scalps. (But that may not be enough for the growth to be significant, so you may need other treatments.)
One survey of more than 750 people found 91% had taken hormones to affirm the gender they identify with. Of them, 59% were transgender men, 31% were trans women, and 9% were nonbinary.
Of all participants, 65% of trans women, 43% of trans men, and 35% of nonbinary people said they had hair loss or thinning on their scalps. Hair loss was more common in transgender men taking masculinizing hormones compared to those who didn't take hormones. Trans women didn't report significant hair loss whether they took hormones or not, according to the survey.
Hair loss got worse for trans men after starting masculinizing hormone therapy, but there wasn't a big change for trans women starting feminizing hormone therapy.
New mothers sometimes find their hair falling out in clumps. Blame it on sinking levels of estrogen after childbirth. The hair usually regrows when the hormones even out.
Menopause is another hormonal trigger for temporary hair loss. Again, your hair will grow back, but it may not be quite as full as before.
A big upset in your life, like a death in the family, a divorce, or unemployment, can cost you a chunk of your hair. A sudden shock or an illness can lead to a condition called telogen effluvium. A large amount of your hair could fall out while you comb or wash it.
Stress also can give some people the urge to pluck hairs from their head, eyebrows, and other places. It’s called trichotillomania, and it’s a way to ease tension, frustration, and other uncomfortable feelings.
Diet and Nutrition
If you lose a lot of weight, more than 15 pounds, you might also lose some of your hair. Other reasons include:
- Too little iron, protein, and other nutrients
- Too much vitamin A (usually from supplements)
- Too little vitamin D (can be corrected by taking supplements). Learn more about the connection between vitamin D and alopecia.
- Anorexia (severely restricting yourself from food) and bulimia (throwing up on purpose after eating)
When a patient comes in with concerns about hair loss, there is a combination of ways to make a diagnosis, Rogers says.
Your doctor can zero in on what’s behind your hair loss with different tests. They’ll probably start with a physical exam and ask about your family history and medical history.
Blood tests. These look for conditions like low iron and thyroid problems.
Hair shaft exam. Your doctor will use a light microscope to check your hair shaft for any disorders.
Pull test. They’ll gently pull a chunk of your hair. It gives a rough idea of how much of your strands are being lost.
Scalp exam. Your doctor will check for any infections or swelling and to see where your hair’s falling out. This can help you find out if you have female pattern hair loss.
Biopsy. Your doctor gently scrapes skin samples from your scalp and sends them to a lab for testing. This can give your doctor a more detailed look at your scalp and hair roots.