While androgenetic alopecia accounts for the majority of hair loss cases, numerous medical conditions can cause or contribute to hair thinning and shedding. Identifying the underlying cause is critical because treating the medical condition — rather than just addressing the hair loss symptom — often leads to the best outcomes.

As a hair restoration specialist, I regularly encounter clients whose hair loss has roots in medical conditions they weren't previously aware of. Part of my role is helping them recognize when their situation warrants medical evaluation and connecting them with the right physicians. Understanding these conditions helps you ask the right questions and advocate for thorough evaluation.

Thyroid Disorders

The thyroid gland regulates metabolism, and thyroid dysfunction is one of the most common medical causes of hair loss. Both hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid) can trigger diffuse hair shedding known as telogen effluvium.

In hypothyroidism, the slowed metabolism affects the hair growth cycle, causing more follicles than usual to enter the resting phase simultaneously. The resulting hair loss is typically diffuse — spread evenly across the scalp — and may also affect the eyebrows and body hair. Hair may become dry, coarse, and brittle.

Hyperthyroidism accelerates the body's metabolic processes, which can also disrupt the hair growth cycle and cause premature shedding. Once thyroid hormone levels are normalized through appropriate medical treatment, hair growth typically resumes, though recovery may take several months.

If you're experiencing unexplained diffuse hair loss, a thyroid panel (TSH, free T3, free T4) is a standard and important part of the diagnostic workup.

Autoimmune Diseases

Autoimmune conditions occur when the immune system mistakenly attacks the body's own tissues, including hair follicles. Several autoimmune diseases are specifically associated with hair loss.

Alopecia Areata

Alopecia areata is an autoimmune condition in which the immune system targets hair follicles, producing smooth, round patches of complete hair loss. It can affect the scalp, face, and body. In severe cases (alopecia totalis or universalis), it can result in complete loss of scalp or body hair.

The course of alopecia areata is unpredictable. Some people experience a single episode with full regrowth, while others develop chronic, recurring patches. Medical treatments including corticosteroid injections, topical immunotherapy, and newer biologic medications can help manage the condition.

Lupus (Systemic Lupus Erythematosus)

Lupus is a systemic autoimmune disease that can affect virtually every organ system, including the skin and scalp. Hair loss in lupus may result from inflammation of the scalp, discoid lesions that scar hair follicles, or the diffuse shedding associated with systemic inflammation.

Lupus-related hair loss can be among the first symptoms that lead to diagnosis. Any unexplained hair loss accompanied by other systemic symptoms — fatigue, joint pain, skin rashes, fever — should prompt evaluation for autoimmune conditions.

Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune condition primarily affecting the joints but associated with systemic inflammation that can contribute to diffuse hair loss. Additionally, some medications used to treat RA may have hair loss as a side effect.

Iron Deficiency Anemia

Iron deficiency is one of the most common nutritional causes of hair loss, particularly in women. Iron is essential for the production of ferritin, a protein that stores iron and is necessary for proper hair follicle function. Low ferritin levels — even without full-blown anemia — can trigger significant shedding.

The hair loss from iron deficiency is typically diffuse, and the hair often regrows once iron levels are restored through supplementation or dietary changes. A comprehensive metabolic panel that includes ferritin levels is a critical diagnostic step for anyone experiencing unexplained hair loss, especially women of childbearing age.

Polycystic Ovary Syndrome (PCOS)

PCOS is a hormonal condition affecting women that is characterized by elevated androgen levels, irregular menstruation, and ovarian cysts. The elevated androgens in PCOS can trigger pattern hair loss in women, often presenting as thinning at the crown and a widening part — the same pattern seen in androgenetic alopecia.

PCOS-related hair loss may be compounded by the metabolic and inflammatory components of the condition. Treatment typically involves addressing the underlying hormonal imbalance, often in collaboration with an endocrinologist or reproductive endocrinologist, alongside standard hair loss treatments.

Diabetes

Both type 1 and type 2 diabetes are associated with increased risk of hair loss. The mechanisms are multifactorial — poor circulation reduces blood flow to hair follicles, hormonal imbalances disrupt the growth cycle, and the inflammatory state associated with diabetes can contribute to follicular damage.

Poorly controlled diabetes is more strongly associated with hair loss than well-managed disease. Maintaining optimal blood sugar levels supports overall vascular health, including the blood supply to hair follicles.

Scalp Infections

Fungal, bacterial, and parasitic infections of the scalp can cause hair loss that is often reversible with appropriate treatment.

Tinea Capitis (Ringworm)

Despite its name, ringworm is a fungal infection, not a worm. It's one of the most common scalp infections causing hair loss, particularly in children but also in adults. The fungus invades hair shafts, causing them to break off at the scalp surface, producing patches of hair loss with broken-off hairs and scaling.

Tinea capitis requires antifungal medication, typically oral griseofulvin or terbinafine, to eradicate the infection. With prompt treatment, hair usually regrows fully.

Folliculitis

Bacterial or fungal infections of hair follicles (folliculitis) can cause hair loss when follicles are damaged or destroyed. Severe or chronic folliculitis — particularly folliculitis decalvans, a scarring form — can result in permanent hair loss in affected areas.

Dermatological Conditions

Several skin conditions that affect the scalp can disrupt hair growth.

Psoriasis

Scalp psoriasis causes thick, silvery scales and inflamed patches that can interfere with hair growth. While psoriasis itself doesn't typically destroy hair follicles, severe inflammation and the trauma of scratching can cause temporary hair loss in affected areas. Treatment of the psoriasis usually allows hair to regrow.

Seborrheic Dermatitis

Seborrheic dermatitis causes greasy, yellowish scales and redness on the scalp. Chronic, severe seborrheic dermatitis can contribute to hair loss through inflammation and follicular stress, though the hair loss is typically reversible once the condition is controlled.

Medications That Cause Hair Loss

Drug-induced hair loss (telogen effluvium or, rarely, anagen effluvium) is a well-documented side effect of numerous medications. Common culprits include:

Beta-blockers and ACE inhibitors used for blood pressure management
Antidepressants including SSRIs and tricyclics
Blood thinners such as heparin and warfarin
Anticonvulsants including valproic acid and carbamazepine
Immunosuppressants used in chemotherapy and autoimmune disease treatment
Retinoids including isotretinoin (Accutane)
Hormonal contraceptives and hormone replacement therapy
NSAIDs with chronic use
Cholesterol-lowering medications such as statins

If you suspect a medication is contributing to hair loss, never discontinue the medication without consulting your prescribing physician. Alternative medications with fewer hair-related side effects may be available, and the benefit-risk calculation should be evaluated by your doctor.

When Hair Loss Signals a Bigger Health Issue

While most hair loss is caused by genetics, certain warning signs should prompt immediate medical evaluation:

Sudden, dramatic shedding
Patchy hair loss with scalp changes (scaling, redness, pain)
Hair loss accompanied by systemic symptoms (fatigue, weight changes, joint pain, fever)
Hair loss that doesn't respond to standard treatments
New onset of hair loss after age 40 without family history
Scalp symptoms including persistent itching, burning, or pain

Hair can be a window into your overall health. Unexplained changes sometimes lead to the early detection of treatable conditions.

My Role in Your Hair Loss Journey

As a hair restoration specialist, I'm not a medical professional, and I don't diagnose or treat medical conditions. However, I've developed a keen eye for recognizing when a client's hair loss pattern may have a medical component that requires physician evaluation.

At my studio in St. Ann, I maintain partnerships with medical professionals in the St. Louis area. When I observe signs that suggest an underlying medical cause, I connect clients with the appropriate specialists for thorough evaluation and treatment. This collaborative approach ensures that no potential cause is overlooked and that you receive comprehensive care.

Understanding the medical landscape of hair loss is the first step toward finding the right treatment path. Whether your loss is genetic, medical, or a combination of both, an informed approach gives you the best chance of successful management.

This article is for educational purposes and does not constitute medical advice. Always consult with a qualified healthcare provider for diagnosis and treatment of hair loss.

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