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8 Illnesses That Cause Hair Loss

Katelyn Hagerty

Reviewed by Katelyn Hagerty, FNP

Written by Sheryl George

Published 02/19/2021

Updated 07/10/2023

File hair loss under things you don’t want to deal with, right up there with making returns and picking an insurance plan. Sigh. Being an adult seemed way more fun in the third grade, right?

Still, it’s important to understand the causes of hair loss so you can figure out the right course of action to keep those hairs on your noggin. In this article, we’ll cover medical conditions that could lead to hair loss, plus potential treatments to help promote new hair regrowth.

If you’ve been seeing a receding hairline or some overall thinning, you have to figure out the root cause to know how to treat it. Several illnesses and medical conditions can be a cause of hair loss, including androgenic alopecia, alopecia areata, nutritional deficiencies, fungal infections, autoimmune disorders, cancer, diabetes and trichotillomania.

Here’s what to know.

Androgenetic Alopecia

This common form of hair loss can affect up to 50 percent of men. That’s a lot of dudes, for real. Sometimes called male pattern hair loss or male pattern baldness, the condition is primarily caused by a predetermined genetic sensitivity to androgens. 

In androgenetic alopecia, a sensitivity to dihydrotestosterone (DHT) causes hair follicles to become smaller and shorter due to a progressively shorter anagen phase, resulting in thinner and shorter hair.

Hair loss tends to occur in bitemporal (the sides or temples of your hairline), vertex (the crown of your head) and mid-frontal scalp areas. This non-scarring alopecia may be reversible if caught early enough.

For a deeper dive, see our guide to androgenetic alopecia.

Alopecia Areata

This autoimmune disease occurs when the immune system attacks anagen hair follicles and sends them prematurely into the catagen phase (when hair stops growing) of your hair growth cycle.

The cause of alopecia areata is not yet understood, but some triggers are thought to include emotional or physical stress, vaccines, drugs and viral infections. While alopecia areata often appears on the scalp, it can also move to other parts of the body.

Read our blog to learn why this happens and how to stop alopecia from spreading.

Onset of alopecia areata usually occurs quickly with patchy bald spots (sometimes called patchy hair loss), as opposed to the gradual thinning typically seen in androgenetic alopecia. It’s been linked to other medical conditions, like thyroid disease, vitiligo, psoriasis, lupus erythematosus, inflammatory bowel disease and rheumatoid arthritis.

Learn more about all the different alopecia types in our comprehensive guide.  

Nutritional Deficiencies

Truly, we wish that Cheetos® were one of the food groups to include in a healthy diet. While they can have their place, a balanced diet filled with vitamins and essential nutrients is critical for healthy hair growth. Like Batman and Robin, they go together.

With that said, nutritional deficiencies can influence both hair growth and structure. Certain vitamin deficiencies can even cause hair loss.

Androgenetic alopecia and telogen effluvium are two prevalent forms of hair loss. Research has indicated that adding small amounts of vitamin D to your diet can help alleviate symptoms associated with these conditions.

We also like soaking up some sunshine in the pursuit of better hair. Bookmark our guide to vitamin D and hair loss for more hair knowledge.

Other issues like iron deficiency can lead to anemia hair loss. Biotin deficiency has been linked to thinning hair as well. Talk to your healthcare provider and get blood tests done to see where your levels fall. If necessary, they can recommend the proper supplements for optimal hair growth.

If you’ve gone through sudden weight loss, you may also experience telogen effluvium hair shedding. Learn more about hair loss and diet in our guide.

Fungal Infections

Fungus is no fun when it’s growing in your bathroom shower, and it’s certainly not a party when it’s growing on your scalp — ugh.

Scalp fungus (or tinea capitis) is a fungal infection that affects your scalp hair. It also goes by the somewhat alarming names herpes tonsurans and ringworm.

The main culprits behind this condition are the dermatophyte species Microsporum and Trichophyton. These fungi have the ability to infiltrate the outer root sheath of your hair follicles and can even make their way into the hair shaft itself. This form of scalp inflammation can lead to hair thinning.

Autoimmune Disorders

A number of autoimmune conditions like thyroid disorders, lupus erythematosus and irritable bowel syndrome can take a toll on your hairline. By the way, we have a full guide on autoimmune diseases that cause hair loss, so bookmark that for some more digging.

Hair loss is also among the common signs of SLE (systemic lupus erythematosus), with upwards of half of patients experiencing it over the course of their illness.

Cancer

While cancer itself doesn’t typically cause hair loss, the medical treatments and drugs used to treat it can cause thinning. Anagen effluvium is a form of hair loss often linked to chemotherapy.

This condition occurs when the anagen hairs are exposed to a harmful or inflammatory substance, which causes the hair shaft to break. Anagen effluvium is also known as chemotherapy-induced alopecia.

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Diabetes

Having diabetes doesn’t just mean you have to watch out for sweets. Insulin resistance can have various side effects, one being hair loss.

Insulin is present in hair follicles and may be involved in regulating androgen metabolism and the hair growth cycle, both of which are important factors in male pattern baldness.

The miniaturization of hair follicles (when your hair follicles get smaller) can also be a factor of diabetes. If you’ve recently been diagnosed with diabetes, you can learn more in our guide to diabetes hair loss.

Trichotillomania

Trichotillomania (TTM) is a long-term impulse-control disorder involving compulsive hair pulling, which can lead to visible hair loss. Onset typically appears in childhood or the teenage years.

It’s often seen along with other mental health disorders, such as anxiety disorders, eating disorders, substance use disorders, mood disorders and personality disorders.

Learn more about stress and hair loss in our guide.

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Depending on the illness and the form of hair loss, treatments can vary. Your dermatologist or healthcare provider can determine which type of hair loss treatment will best work with your medical condition.

Here are a few options they might recommend:

  • Finasteride. FDA-approved to treat androgenetic alopecia, this oral treatment is a 5-alpha-reductase isoenzyme that helps block the conversion of hormones responsible for thinning hair seen in androgenetic alopecia.

  • Topical finasteride & minoxidil spray. This quick-drying spray combines two gold-star treatments, finasteride and minoxidil, to effectively treat shrinking hair follicles from multiple pathways.

  • Minoxidil 5% foam. Minoxidil is FDA-approved for androgenetic alopecia. It’s also used off-label to treat various hair loss disorders, including alopecia areata, telogen effluvium, anagen effluvium and chemotherapy-induced alopecia. Studies have shown improved hair growth within various causes of hair loss. A 2% minoxidil solution is also available for those who may have more sensitive scalps.

Hair loss treatments, delivered

From nutritional deficiencies to hypothyroidism and diabetes, many medical conditions can cause hair loss. Here’s what to keep in mind:

  • Make a move. Whether you’re noticing signs of male pattern baldness or are having more concerning issues like insulin resistance, don’t just ignore your symptoms. Things won’t just magically go away (except money, which seems to disappear pretty quick).

  • Speak with a pro. While you may be used to Googling everything or asking your best bud for advice, our rec is to speak with a dermatologist or another healthcare professional if you’re noticing hair loss. You want to rule out any underlying causes and get the appropriate attention and care for your condition. Your provider can determine the right hair loss treatments you may need.

  • Get treated. Whether it’s a combination of therapies, like medication for your illness, a hair loss treatment or supplements, treatment options can help slow down or even reverse hair loss. For instance, minoxidil has shown success in varying forms of hair loss conditions.

If you’re ready to get started, take this easy quiz to set up an online hair consultation.

9 Sources

  1. Katta, R., & Guo, E. (2017, January 31). Diet and hair loss: effects of nutrient deficiency and supplement use. NCBI. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5315033/
  2. Almohanna, H., Ahmed, A., Tsatalis, J., & Tosti, A. (2018, December 13). The Role of Vitamins and Minerals in Hair Loss: A Review. NCBI. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6380979/
  3. Al Aboud, A. M., & Crane, J. S. (2023, April 16). Tinea Capitis - StatPearls. NCBI. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK536909/
  4. Popa, A., Carsote, M., Cretoiu, D., Dumitrascu, M., Nistor, C. E., & Sandru, F. (2023, January 31). Study of the Thyroid Profile of Patients with Alopecia. NCBI. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9918246/
  5. Saleh, D., Nassereddin, A., & Cook, C. (2022, August 8). Anagen Effluvium - StatPearls. NCBI. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK482293/
  6. Bakry, O. A., Moneim Shoeib, M. A., Kamel El Shafiee, M., & Hassan, A. (2014, September). Androgenetic alopecia, metabolic syndrome, and insulin resistance: Is there any association? A case–control study. NCBI. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4144211/
  7. Franklin, M. E., Zagrabbe, K., & Benavides, K. L. (2011, August 11). Trichotillomania and its treatment: a review and recommendations. NCBI. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3190970/
  8. Suchnowanit, Poonkiat, Thammaruchu, Sasima & Leerunyakul, Kanchana. (2019, Aug 9) Minoxidil and its use in hair disorders: a review. NCBI. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6691938/
  9. Moghadam-Kia S and Franks AG. Autoimmune Disease and Hair Loss. Dermatologic Clinics. (2023, January). Retrieved from https://www.derm.theclinics.com/article/S0733-8635(12)00096-4/fulltext
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