Personalized hair loss therapy – how DNA analysis can optimize treatment

Ruslan Dorfman, PhD, MBA29 Oct 2026

Hair loss, or alopecia, can affect the scalp or the whole body and may be temporary or permanent. It can result from genetics, hormonal changes, thyroid problems, stress, medications or autoimmune disease. Men often notice a receding hairline or thinning on the crown, but women are also commonly affected. Because the causes differ, an accurate diagnosis by a doctor or dermatologist is the first step. Once treatment is chosen, your genes and your other medications can affect how safe and effective it is. This article explains the main types of hair loss, how they are treated and how pharmacogenetic testing can help.

What are the main types of hair loss?

Pattern hair loss (androgenetic alopecia)

Pattern hair loss is the most common type. It runs in families and is driven by dihydrotestosterone (DHT), a hormone made from testosterone. Hundreds of genetic variants contribute to the risk. In men, it causes a receding hairline and thinning on the crown. In women, it usually causes thinning along the part and top of the head.

Thyroid-related hair loss

Both an underactive thyroid (hypothyroidism) and an overactive thyroid (hyperthyroidism) can cause diffuse thinning and brittle hair. Hair usually improves once thyroid levels are treated. Your doctor may also check for iron deficiency, which is another common and treatable cause of hair shedding.

Alopecia areata

Alopecia areata is an autoimmune condition in which the immune system attacks hair follicles, causing round bald patches or, in severe cases, loss of all scalp or body hair. People with alopecia areata are more likely to have other autoimmune conditions, such as thyroid disease, atopic dermatitis and some types of inflammatory arthritis, and also anxiety and depression. Genetic studies show that alopecia areata shares risk genes, including HLA genes, with other autoimmune diseases.

Scarring alopecias

Frontal fibrosing alopecia (FFA) causes a slowly receding hairline at the front and sides of the scalp and often affects the eyebrows. It is most common in women after menopause. Its cause is not fully understood, but genetic studies have linked it to certain HLA types and to variants in the ERAP1 gene, and women who carry both have a several-fold higher risk.

Central centrifugal cicatricial alopecia (CCCA) causes scarring hair loss that starts at the crown. It is most common in Black women. Early treatment with anti-inflammatory medications helps prevent permanent loss, and small studies suggest that metformin applied to the skin or taken by mouth may help.

Stress, mood and medications

Telogen effluvium is heavy shedding that starts two to three months after a major stress, illness, childbirth, rapid weight loss or a new medication. It usually recovers on its own. Hair shedding reported with weight loss medications such as semaglutide (Ozempic, Wegovy) is often this type. Trichotillomania (hair-pulling disorder) is a mental health condition that causes patchy hair loss and is treated with behavioural therapy and, sometimes, medication.

Some medications can cause hair thinning, including methotrexate and leflunomide used for rheumatoid arthritis, some antidepressants and mood stabilizers, and chemotherapy.

How is hair loss treated?

Minoxidil is the most widely used treatment. Topical minoxidil (Rogaine) is approved for pattern hair loss in men and women. Low-dose oral minoxidil, a blood pressure tablet (Loniten) used off-label at much lower doses, is increasingly prescribed. In a 2024 trial in men, oral minoxidil 5 mg a day did not work better than topical 5% minoxidil overall, and about half of the men taking it grew unwanted body hair. Oral minoxidil can also cause dizziness, a fast heartbeat and fluid retention. Minoxidil must be activated in the hair follicle by an enzyme called sulfotransferase (SULT1A1), and small studies suggest that the activity of this enzyme can help predict who responds.

Finasteride (Propecia) blocks the conversion of testosterone to DHT and is approved for male pattern hair loss. It lowers PSA, a blood test used to screen for prostate cancer, by about half, so your doctor needs to know you take it when reading PSA results. Sexual side effects occur in a small percentage of men and, rarely, may persist after stopping. Product labels also warn about depression and suicidal thoughts. Women who are or may become pregnant must not take it or handle crushed tablets.

Spironolactone (Aldactone) blocks the effects of male hormones and is used off-label for female pattern hair loss. It is not used for men because of its feminizing effects. It can raise potassium levels, especially with some blood pressure medications or potassium supplements, and must not be used during pregnancy.

JAK inhibitors are newer tablets for severe alopecia areata. In clinical trials, about one in three people taking baricitinib (Olumiant) 4 mg and about one in four taking ritlecitinib (Litfulo) 50 mg regained most of their scalp hair after six to nine months, compared with only a few percent on placebo. Deuruxolitinib (Leqselvi) was approved in the US in 2024. These medications carry warnings about serious infections, blood clots, heart problems and some cancers, so they need careful monitoring. Ask your dermatologist which are available and covered in Canada.

Corticosteroids, such as triamcinolone (Kenalog) injected into bald patches, are a common treatment for limited alopecia areata and scarring alopecias.

Which genes and drug interactions affect hair loss medications?

Medication	Brand name	Used for	Genes and enzymes	Interactions and cautions
Deuruxolitinib	Leqselvi (US)	Severe alopecia areata	CYP2C9	Not for CYP2C9 poor metabolizers. Avoid with fluconazole.
Ritlecitinib	Litfulo	Severe alopecia areata	Several enzymes (GST, CYP3A4 and others)	Interacts with some other medications.
Baricitinib	Olumiant	Severe alopecia areata, rheumatoid arthritis	Mostly removed by the kidneys	Lower dose for kidney problems.
Finasteride	Propecia	Male pattern hair loss	CYP3A4	Lowers PSA. Not for pregnancy.
Spironolactone	Aldactone	Female pattern hair loss (off-label)	No major genetic effect	Can raise potassium. Not for pregnancy.
Minoxidil	Rogaine (topical), Loniten (oral)	Pattern hair loss	SULT1A1 (activation in the hair follicle)	Oral form lowers blood pressure.
Triamcinolone	Kenalog	Alopecia areata, scarring alopecia (injection)	CYP3A4	Avoid with ritonavir and some antifungals.
Sulfasalazine	Salazopyrin	Rheumatoid arthritis, inflammatory bowel disease (limited evidence for alopecia)	G6PD, NAT2	Risk of anemia with G6PD deficiency. More side effects in NAT2 slow acetylators.

Drug interactions can have the same effect as a gene variant. For example, a person with normal CYP2C9 genes who takes fluconazole can process deuruxolitinib as slowly as a CYP2C9 poor metabolizer. This is why your genes and your full medication list should be reviewed together.

Why does ancestry matter for genetic testing?

Your ancestry affects which gene variants you are likely to carry. Some variants that reduce enzyme activity are common in one population and rare in others. For example, CYP2C9*8 is relatively common in people of African ancestry (about 6% of gene copies) and rare in other groups. A test that does not include it can miss reduced CYP2C9 function, which matters for drugs such as deuruxolitinib. Choose a test that analyzes multiple variants for accurate results.

G6PD deficiency is most common in people of African, Mediterranean, Middle Eastern and Asian ancestry. It is more often severe in men, but women can be affected too.

How does hair loss affect mental health?

Hair loss can have a large emotional impact. People with alopecia areata are more likely to develop anxiety, depression and adjustment disorders. Managing these conditions, along with any related autoimmune disease, is an important part of care. Many people with hair loss also take antidepressants or anxiety medications, which adds to the number of medications to check for interactions.

How can a pharmacogenetic test help?

Genetic tests for the risk of hair loss itself do not change treatment and are not recommended. A pharmacogenetic test is different: it shows how your body processes medications. The deuruxolitinib label, for example, says it must not be used by CYP2C9 poor metabolizers, which only a genetic test can identify.

A Pillcheck test reports CYP2C9, CYP3A4, G6PD and NAT2, along with genes that affect antidepressants, anxiety medications and many medications for autoimmune conditions. Pillcheck reports on 24 genes, increasing coverage with new guidelines and drug labels (see the genes tab), and covers 355 medications, which account for over 70% of dispensed prescriptions. A Pillcheck pharmacist reviews your results together with all your medications, checks for interactions and gives you recommendations to discuss with your doctor or dermatologist. Always check with your pharmacist before starting a new medication or supplement, even one that does not need a prescription.

Summary

Hair loss has many causes, including genetics, hormones, thyroid disease, stress, medications and autoimmune disease, so an accurate diagnosis comes first.
Minoxidil, finasteride, spironolactone, corticosteroid injections and newer JAK inhibitors work for different types of hair loss and have different risks.
Genes such as CYP2C9, CYP3A4, G6PD and NAT2, and drug interactions, can affect the safety of hair loss medications.
People with alopecia areata are more likely to have other autoimmune and mental health conditions that also need treatment.
A pharmacogenetic test with a pharmacist review can help you and your doctor choose safer medications and doses.

Frequently asked questions

Is oral minoxidil better than minoxidil foam or solution?

Not necessarily. In a 2024 trial in men, oral minoxidil did not work better than topical minoxidil overall, and it caused more unwanted body hair. Oral minoxidil may suit people who cannot use a topical product. Your doctor can help you decide.

Can a DNA test tell me if I will go bald?

Not reliably. Pattern hair loss depends on hundreds of genetic variants and other factors, and testing for them does not change treatment. A pharmacogenetic test is more useful because it guides the safety of medications you may take.

Is finasteride safe?

Most men tolerate finasteride well. A small percentage have sexual side effects, and labels warn about depression and suicidal thoughts. Tell your doctor if you notice any mood changes. It also lowers PSA results.

Does Pillcheck test for alopecia risk genes?

No. Pillcheck does not test for the risk of hair loss, and it does not report HLA genes. It shows how your genes affect your response to medications, including some used for hair loss and related conditions.