What Causes Hair Loss?

Learn why women lose their hair, what you can do to re-grow yours, and when it might be time to see your doctor.

Sanaz Majd, MD
5-minute read

Having a long, thick, and healthy mane is regarded as a sign of beauty in our current culture. Hair implants for men is a thriving business. Celebrities have made hair extensions a rather expensive fad. More and more women opt for wigs, and men for toupees than ever before. Our society just might  be obsessed with having a head full of hair.

So when women lose hair, it’s a big deal. Women know when they are losing hair, even if it is not visible to the outsider, and it can be worrisome, saddening, and even traumatizing.

What Causes Hair Loss?

Andrea came to my office in tears. She had always had a full head of hair, and within the last six months she’s noticed quite a drastic change—an overall thinning of her hair. She wanted to know why she was losing so much hair. I’ll tell you what I told her; there are 7 common causes of alopecia, otherwise known as hair loss:

  • Genetics: This is by far the most common cause of hair loss. Genes are responsible for hair loss in both men and women, and hair loss related to genetics may begin as early as age 12. The loss of hair is diffuse and all over the entire scalp--and not just in one spot or patch;--but is worse in the front or sides of the scalp. Andrea’s dad suffers from male-pattern baldness.

  • Pregnancy: Many women lose some hair throughout the pregnancy or after delivery. This is usually reversible, and most regrow their hair with time. Andrea was not pregnant.

  • Thyroid Disorders: Many patients with abnormal thyroid hormone levels can experience hair loss. Andrea’s blood test for a thyroid condition was normal.

  • PCOS: Elevated testosterone levels cause a diffuse thinning of the scalp in women, and that’s why many women with Polycystic Ovarian Syndrome, a condition marked by irregular periods, acne, and abnormal facial/body hair experience hair loss. Andrea’s periods are regular, and she has never had a problem with acne or excessive body/facial hair. To read more about PCOS, refer to my previous article, “What is Polycystic Ovarian Syndrome (PCOS)?

  • Autoimmune Attack: The body can produce certain proteins that attack its own hair follicles. Patients with this type of hair loss typically have a very distinct area of hair loss, and the rest of the scalp is unaffected. But Andrea’s hair loss was diffuse, and she didn’t have any distinct pattern of hair loss.

  • Damaged Hair Follicles: A number of things can damage the hair follicles: 

    • chemicals applied to the scalp
    • infections of the scalp
    • radiation or chemotherapy
    • certain crash/liquid protein diets
    • medications (like hormones and anti-seizure medications)

Andrea told me that none of those applied to her

  • Stress: Stress can also cause a rather diffuse pattern of hair loss all over, and the hair loss typically begins 2-4 months after experiencing a rather traumatic stressful life event. It can last several months, but it is reversible. With time, most women regrow their hair. Andrea finally confessed that she broke up with her boyfriend of eight years about three months ago and has been very depressed since. We have our cause. 


Please note that all content here is strictly for informational purposes only. This content does not substitute any medical advice, and does not replace any medical judgment or reasoning by your own personal health provider. Please always seek a licensed physician in your area regarding all health related questions and issues.

About the Author

Sanaz Majd, MD

Dr. Sanaz Majd is a board-certified Family Medicine physician who graduated from Drexel University College of Medicine in Philadelphia. Her special interests are women's health and patient education.