What causes hair loss?
Androgenic alopecia causes hair loss in both men and women. It is hereditary and is the most common cause of hair loss. This type of hair thinning is symmetrical. It spreads over a large area and progresses over time.
Androgenic Alopecia / Male Pattern Baldness in Men – Orange County Hair Restoration had these statistics on male pattern baldness.
- Usually starts in your 20s or 30s and is causes 95% of hair loss in men.
- By age 35, over 60% of American men have some hair loss.
- By age 50, almost 85% of men have significantly thinning hair.
- In men, hair typically, recedes in a distinct pattern, beginning at the front of the hairline and temples or at the bald spot on the back of the head – and ultimately leaves a thin “C” of hair.
- Follicles make finer, lighter hairs until finally hair production stops.
Androgenic Alopecia / Female Pattern Hair Loss – As mentioned above, women also inherit androgenic alopecia. The North American Hair Research Society gives the following statistics on female pattern hair loss.
- Androgenic alopecia occurs in approximately half of women by the age of 50.
- This hair loss starts later in life and is evenly spread.
- Women rarely go completely bald.
- Instead, thinning usually affects the entire top of the head (but can also affect all areas of the head).
- Women may say their ponytail isn’t as thick – or that they can see their scalp more easily than before.
- Hair becomes finer, lighter and has a shorter growth phase.
To Understand Hair Loss, You Have to Understand the Hair Cycle
Hair grows from the hair follicle under the skin. The dermal papilla is the part of a hair follicle that is responsible for hair growth. This is where the cells in the root of the hair divide and differentiate to form a new hair follicle. The papilla directly contacts the capillaries in the skin and brings nutrients for follicle growth. The papilla has many androgen receptors (men have more receptors here than women).There are four stages in the life cycle of a hair and each hair is at a different stage of this cycle. Most people have 25 to 30 hair cycles in a lifetime.
- Anagen / Growth – Over time, the length of the growth stage shortens. Hair can become weaker and thinner after each cycle. Adding supplements to your diet may prevent this thinning. The growth lasts anywhere from 2 – 7 years and determines the length of our hair. About 90% of our hair is in this growth phase at one time.
- Catagen / Transition – In this phase, the hair follicle shrinks and detaches from the dermal papilla. The transition phase lasts about 10 days.
- Telogen / Resting – Around 10-15 percent of our hairs are in this phase which lasts about 3 months. If hairs enter the resting phase too early, noticeable thinning can occur. While the old hair rests, a new hair starts to grow in the follicle.
- Exogen / Shedding – Hair is released from the follicle then shed, and a new hair continues to grow. In normal hair shedding about 50 to 150 hairs fall out each day. In the chart above, the exogen phase is shown as “early anagen.”
How Androgenic Alopecia Progresses in Men and Women
Testosterone levels play a big role in hair loss. When combined with another enzyme (5 alpha reductase) in the hair follicle, testosterone converts to dihydrotestosterone (DHT), a type of androgen. When the healthy hair follicle is exposed to DHT and other androgens for long periods, it shrinks. Hair progressively gets thinner, shorter, and more brittle with a weaker shaft. Some of the hair follicles eventually die. This cycle is called miniaturization.
Miniaturization in androgenic alopecia is due to heredity, the presence of DHT, and age. Some people are born with a genetic predisposition to miniaturization. In these people, DHT interferes with hair growth.
- The more DHT, the more hair is lost.
- Androgen hormones are dominant in men, but are present in smaller amounts in women; so androgens cause more hair loss in men than they do in women.
DHT shrinks hair follicles so they get a reduced flow of blood & nutrients.
DHT shrinks hair follicles so they get a reduced flow of blood & nutrients.
One (or More) of the Following also Cause Hair Loss:
Although androgenic alopecia is the most common type of hair loss in women, thinning hair in females can have many different causes. So it's important that your doctor use diagnostic testing to rule out any underlying physical condition. A correct diagnosis will get you the best treatment and the best result.
These are some of the tests your doctor may use:
- A scalp biopsy can help to determine the cause of hair loss.
- A hair pull test will determine if there is excessive hair loss.
- Densitometry checks for miniaturization of the hair shaft.
- Blood tests evaluate hormone levels.
These are the other things (besides androgenic alopecia) that could be causing your hair loss:
- Diseases – Thyroid disorders, polycystic ovary syndrome, anemia, chronic illness, and some medications can cause hair loss in women. Certain types of autoimmune disorders can cause alopecia areata — an inflammatory condition where hair comes out in clumps or patches. Hair loss can also be caused by low levels of vitamins A and D, iron or other nutrients.
- Stress – Telogen Effluvium causes hair loss following physical trauma such as childbirth, a restrictive diet, or surgery. Hair starts to come out in large clumps as late as 3 months after an event, but grows back when your body recovers.
- Damage to Hair Follicles – Traction Alopecia happens when hair follicles are damaged by hair being pulled too tight. Braiding, cornrows, tight ponytails, and hair extensions can cause this type of hair loss.
- Chemotherapy – Anagen Effluvium is hair loss caused by low metabolic activity of the hair follicle. The same toxic effects of chemotherapy that stop the cancer cells from growing and dividing also negatively impact hair follicles.
- Changes in Hormone Levels – Thinning hair is common in women during menopause and peri-menopause because of changing hormone levels and an imbalance in estrogen and testosterone. Contraceptives and medications that change hormone levels can also cause hair loss. Progestin implants (Norplant), hormone injections (Depo-Provera), birth control skin patches (Ortho Evra), and vaginal rings (Nuvaring) may all cause thinning hair in women with a family history of hormone induced hair loss. If there is a family history of hair loss, it is best to use a contraceptive with the lowest androgen index.
- A Poor Diet causes hair loss. Low levels of vitamins A and D, iron, protein and other nutrients are essential for hair growth.
- Medications like methotrexate, lithium, NSAIDS, anabolic steroids, and some anti-depressants may cause hair loss.
- Aging generally causes hair loss.
Early Treatment is Important!
When hair loss starts, early intervention is needed to prevent more hair loss. Any delay in treatment can cause a permanent loss of hair follicles.
Although androgenic alopecia is the most common cause of hair loss, women especially can have an underlying physical condition that is contributing to their thinning hair. So it's really important to see a doctor to ensure you get the correct treatment for your thinning hair.
Now read our post about hair loss treatment, 5 of the Most Effective Ways to Treat Hair Loss - Without Surgery!
And learn more about PRP and how it can help regrow hair in, Platelet Rich Plasma - How It Restores Skin, Scars & Hair.
Amy Takken is a registered nurse with 20+ years of experience helping people improve their health. Her in-depth skincare articles have been featured on Nazarian Plastic Surgery and The Palm Beach Center for Facial Plastic & Laser Surgery. Amy loves research and constantly watches for new products and treatments to help you improve your skin’s health – because healthy skin is beautiful! To reach Amy, visit our contact page.
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The Information provided on our website is not medical advice and should not be viewed as such. By law, only a medical doctor can diagnose or give medical advice. As a registered nurse, my goal is to educate, so I provide information on skin care, skin care products, and skin care treatments. If you have any condition that concerns you, please see a medical doctor. While most skin conditions are benign, some – like melanoma – can be deadly. If there is any doubt, please, please consult your physician. Thank you!