Testosterone is converted to Dihydrotestosterone (DHT) by 5 Alpha Reductase (5AR) Enzyme. DHT attaches to the androgen receptors on the hair follicle.
DHT causes increased hair loss; gradually miniaturizing the hair follicle.
This miniaturized hair follicle eventually dies and hair loss occurs.
9 Causes of Hair Loss in Women
Everyone loses hair. It happens during your morning shower, while you're blowing it dry, or when you give it a quick brush—and that's normal. "On average, we lose fifty to a hundred hairs a day," says Francesca Fusco, MD, a New York City dermatologist who specializes in hair loss. "That's just hair going through its cycles, and there will be a new one to replace it." But hair loss may be a sign of a more serious medical condition that needs an evaluation by a dermatologist and possible treatment. Here are nine causes of hair loss and how to deal with them.
Telogen effluvium is a phenomenon that occurs after pregnancy, major surgery, drastic weight loss, or extreme stress, in which you shed large amounts of hair every day, usually when shampooing, styling, or brushing. It can also be a side effect of certain medications, such as antidepressants, beta-blockers, and nonsteroidal anti-inflammatory drugs. During telogen effluvium, hair shifts faster than normal from its growing phase into the "resting" phase before moving quickly into the shedding, or telogen, phase.
The symptoms: Women with telogen effluvium typically notice hair loss 6 weeks to 3 months after a stressful event. At its peak, you may lose handfuls of hair.
The tests: There are no tests for telogen effluvium, but your doctor may ask you about recent life events and look for small "club- shaped" bulbs on the fallen hair's roots. The bulbs mean the hair has gone through a complete cycle of growth, suggesting that the cycle may have sped up due to stress.
What you can do: In some cases, such as pregnancy or major surgery, you may have to bide your time until the hair loss slows. If medication is the culprit, talk to your doctor about lowering your dosage or switching drugs. If it's stress-related, do your best to reduce anxiety.
Hereditary Hair Loss
Hair loss that is genetic is known as androgenetic alopecia and, according to the American Academy of Dermatology, is the most common cause of hair loss. The gene can be inherited from either your mother's or father's side of the family, though you're more likely to have it if both of your parents had hair loss.
The symptoms: Women with this trait tend to develop thinning at the hairline behind the bangs, says Pamela Jakubowicz, MD, a dermatologist at Montefiore Medical Center in New York City. The condition develops slowly and may start as early as your 20s. You may be vulnerable if your mother also has this pattern of thinning. In some cases, the hair loss may be diffuse, meaning it's spread across the entire scalp.
The tests: Your dermatologist will examine the pattern of hair loss to determine if it's hereditary and may order blood work to rule out other causes, Dr. Jakubowicz says. A biopsy of your scalp is sometimes done to see if the hair follicles have been replaced with miniaturized follicles, a surefire sign of hereditary hair loss.
What you can do: Slow the hair loss by applying minoxidil (Rogaine) to the scalp twice a day. The drug works on both women and men, although women should use a lower-strength formula to prevent unnecessary side effects. Women should not use minoxidil if they are pregnant or nursing. Men may be treated with finasteride (Propecia), an oral medication.
Millions of people, most of them women, suffer from thyroid disease. When your body produces too little thyroid hormone, the hormone responsible for metabolism, heart rate, and mood, you are said to have hypothyroidism, or an underactive thyroid. If your body makes too much of the hormone, you're said to have hyperthyroidism, or an overactive thyroid. Thyroid hormone is responsible for everything from your basal metabolic rate—the rate at which your body uses oxygen and energy to function—to the growth of your hair, skin, and nails. But when you don't have the right amount, you may notice changes in bodily functions.
The symptoms: Hypothyroidism (too little hormone) may cause a host of symptoms, including unexplained weight gain, fatigue, constipation, depression, and difficulty concentrating. Hair, nails, and skin may become more brittle and break more easily. It's more common in women, especially over the age of 50, says Theodore C. Friedman, MD, MPH, chief of the division of endocrinology, metabolism, and molecular medicine at Charles Drew University in Los Angeles and coauthor of The Everything Guide to Thyroid Disease (Adams Media, 2007). It affects about 5 percent of the US population but is nearly 10 times more frequent in women.
Hyperthyroidism (too much hormone) may cause inexplicable weight loss, heart palpitations, nervousness, irritability, diarrhea, moist skin, muscle weakness, and a startled appearance of the eyes. You may also experience hair loss as metabolism speeds up. Hyperthyroidism is much less common than hypothyroidism and affects about 1 percent of the US population.
The tests: A blood test measures thyroid-stimulating hormone, which is produced by the pituitary gland in an attempt to coax the thyroid to make thyroid hormone. Excess TSH usually indicates hypothyroidism, while abnormally low levels suggest hyperthyroidism.
What you can do: Your doctor may prescribe a thyroid hormone medication to restore levels to normal. Regular TSH tests might be done to ensure an adequate dosage.
Lupus is a chronic autoimmune disease in which the body's own immune system attacks healthy tissues. The condition affects about 1.5 million people and tends to strike women during their childbearing years.
The symptoms: Lupus often causes extreme fatigue, headaches, oral ulcers, and painful, swollen joints. Many people develop a butterfly-shaped rash across the bridge of the nose and become more sensitive to the sun. Other symptoms include fever; swelling in the feet and hands and around the eyes; chest pain; and anemia. Many people also experience hair loss, which may be mild and occur while shampooing or brushing your hair—or it may be more severe, coming out in patches and accompanied by a rash on the scalp, says Arthur Weinstein, MD, director of the division of rheumatology at the Washington Hospital Center. Because these symptoms occur in many other conditions, lupus is often called the great imitator.
The tests: A rheumatologist will examine joints and other tissues for signs of inflammation, such as heat, pain, swelling, and redness. A blood test to measure levels of anti-nuclear antibodies (ANA) may also indicate lupus. Rheumatologists will also determine if patients have four of 11 diagnostic criteria set by the American College of Rheumatology, though fewer criteria along with a skin biopsy may sometimes indicate lupus, Dr. Weinstein says.
What you can do: See a rheumatologist if your hair loss is accompanied by joint pain, fatigue, and other symptoms of lupus, which is treated with oral medications such as prednisone. If you also have a rash on the scalp, you need to see a dermatologist, who is likely to prescribe a topical cream.
Women who have heavy periods or don't eat enough iron-rich foods may be prone to iron deficiency, in which the blood doesn't have enough red blood cells. Red blood cells transport oxygen to cells throughout your body, giving you the energy you need.
The symptoms: Iron deficiency anemia causes extreme fatigue, weakness, and pale skin. You may also notice headaches, difficulty concentrating, cold hands and feet, and hair loss. Any type of exertion may leave you short of breath.
The tests: A blood test to measure ferritin, the protein that stores iron in your body, is usually needed to diagnose iron-deficiency anemia. Your doctor may also check your blood level of hematocrit, which gauges how much of your blood is made up of red blood cells.
What you can do: Eat iron-rich foods such as beef, pork, fish, leafy greens, fortified cereals, and beans—preferably, along with foods rich in vitamin C, which enhances iron absorption. Women need 18 mg of iron a day, 8 mg after menopause; ask your doctor if you should take an iron supplement. You can also find supplements specifically for hair loss, Dr. Fusco says. Key ingredients may include biotin, silica, and L-cysteine, in addition to iron.
Polycystic Ovarian Syndrome
As many as five million women in the United States suffer from polycystic ovarian syndrome. The condition, which can begin as early as age 11, is caused by a hormonal imbalance in which the ovaries produce too many male hormones. PCOS often causes infertility.
The symptoms: PCOS can cause facial hair growth, irregular periods, acne, and cysts on the ovaries. And while you may experience hair loss on your scalp, you may notice more hair elsewhere on the body, Dr. Fusco says.
The tests: Your doctor is likely to do a blood test to look for elevated levels of testosterone and DHEAS (dehydroepiandrosterone), a by-product of testosterone.
What you can do: Most cases of PCOS are treated with birth control pills such as Yasmin, which contains a potent anti-androgen that blocks testosterone. If you can't use birth control pills, your doctor may prescribe spironolactone (Aldactone), which also blocks male hormones. Losing weight can also help by decreasing the effect of the male hormones.
An unhealthy scalp can cause inflammation that makes it difficult for hair to grow. Skin conditions that lead to hair loss include seborrheic dermatitis (dandruff), psoriasis, and fungal infections such as ringworm.
The symptoms: Seborrheic dermatitis causes the scalp to shed its skin, so you'll notice greasy, yellowish scales on your shoulders or in your hair. It may be the result of yeast called Malassezia, hormonal changes, or excess oil in the skin. Psoriasis, an autoimmune condition that causes excessive skin cell turnover, produces a very thick white scale on the scalp that can bleed if pulled off. With ringworm, a fungus you contract by touching an infected person or animal, you'll notice red patches on your scalp, which may be diffuse, Jakubowicz says.
The tests: A physical exam of the scalp will help determine which condition you have. A fungal culture and possibly a biopsy of the scalp may pinpoint ringworm.
What you can do: Each condition usually requires a prescription: a medicated shampoo for seborrheic dermatitis, medications or light therapy for psoriasis, and oral antifungals for ringworm.
Alopecia areata is an autoimmune disorder in which the immune system attacks hair follicles. It affects about 4.7 million people in the United States and occurs equally in men and women. The cause is unknown, but it may be triggered by stress or illness.
The symptoms: The condition can occur in three forms. Alopecia areata commonly causes round, smooth patches of baldness on the scalp, eyebrows, or legs, Dr. Fusco says. Total hair loss on the head is known as alopecia totalis, while hair loss that occurs all over the body is called alopecia universalis. "Some patients have reported that before the bald spot occurred, they felt something in that area—a tingling or an irritation," Dr. Fusco says.
The tests: Observing the pattern of hair loss can usually determine if you have alopecia areata, and blood tests for iron stores, ANAs. and hormones are usually done to rule out underlying conditions that may cause hair loss.
What you can do: Alopecia areata is usually treated with intralesional corticosteroids, Dr. Fusco says. In some cases, minoxidil (Rogaine) may also help. It's also important to reduce stress.
Too much shampooing, styling, and dyeing can harm your tresses. Heat and chemicals weaken the hair, causing it to break and fall out. Often, it's a combination of treatments—keratin, coloring, and blow-drying, for instance—that does the damage.
The symptoms: If the fallout is occurring from external damage caused by styling, it will simply break, and you won't see those club-shaped telogen bulbs at the ends.
The tests: Dr. Jakubowicz does a pull test: She takes a small handful of about 50 strands, pulls gently, and checks to see whether the hair that comes out has bulbs on the ends.
What you can do: Avoid using appliances that overheat your hair. Set your hair dryer on cool and low settings, and minimize your use of flat irons. Don't dye your hair more than one or two shades its normal color: The more severe the color change, the more chemicals you require, which can make hair break. If you use hair gel or hair spray, don't wait for it to dry before you comb through it, because the hair will harden and be more likely to break.
The condition of your hair doesn't just affect your looks—it's an important indicator of your health. If you're experiencing hair loss, talk to your dermatologist.