Hair loss 1/2: what your body is trying to tell you

A few more hairs in your brush, on your pillow, or in the shower? It is not always easy to know whether this is normal... or a real warning sign.

Because yes, we all lose hair every day. Some daily shedding is part of the normal hair cycle. The hair follicle works in cycles: a growth phase, a transition phase, then a resting phase before shedding.

But when hair density visibly decreases, the part starts to widen, the temples thin out, or shedding becomes unusual and persistent, this is no longer simply part of the normal cycle.

Hair loss is often a reflection of an underlying biological, hormonal, nutritional, or inflammatory terrain that needs to be understood.

And above all: it is not inevitable. The earlier the cause is identified, the more effectively it can be addressed.

What is normal... and what deserves further investigation

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What remains within the normal range

• Mild, diffuse shedding with no visible thinning areas, without a noticeable change from your usual baseline

• No sudden change in volume or density over a few weeks

Signs that should prompt us to look deeper

• Significant hair loss that persists

• A widening part

• Loss of density at the crown

• Receding temples or hairline

• Sudden shedding a few weeks or months after stress, illness, childbirth, surgery, or a hormonal change

• Hair that becomes finer, more brittle, and less dense than before

Why are you losing your hair? The key underlying factors to know

Main causes of hair loss

Hair loss is rarely caused by just one factor. In real life, several mechanisms often overlap.

1. Deficiencies or insufficient intake: when the follicle lacks resources

The hair follicle is a highly metabolically active tissue. To maintain its growth phase, it needs energy, protein, iron, and several micronutrients.

Among the factors most often found in lab work:

• Low ferritin / iron deficiency, sometimes even without overt anemia

• Low vitamin D

• Low zinc

• Sometimes B12 or folate, depending on dietary or digestive context

What you may notice: diffuse shedding, finer hair, duller hair, less regrowth, overall loss of density.

Useful biomarkers: CBC, ferritin, iron, transferrin saturation, vitamin D, B12, folate, zinc.

2. Hormones: androgens, estrogens, and thyroid

Hair is highly sensitive to the hormonal environment.

Androgens and DHT

In both men and women, some forms of hair loss are linked to progressive follicle miniaturization, classically under androgen influence. In women, this often appears as a widening of the central part and reduced density on the top of the scalp. In men, the pattern is more classic: temples, vertex, and hairline.

In some women, this pattern may be encouraged by androgen excess, particularly in the context of PCOS.

Estrogens

Female hormonal shifts also matter. A sharp drop in estrogen can promote increased shedding, especially after childbirth or after stopping an estrogen-containing treatment. This is also one reason why some women notice changes in their hair during perimenopause and after menopause.

Thyroid

The thyroid plays an important role in normal follicle function. Both hypothyroidism and hyperthyroidism can be associated with diffuse hair loss. This is an axis that should not be overlooked, especially if the hair loss is accompanied by other signs such as fatigue, feeling cold, constipation, palpitations, weight loss or gain, cycle irregularities, or skin changes.

Useful biomarkers: TSH, free T4, free T3, thyroid antibodies, total and free testosterone, SHBG, DHEA-S, and depending on the context, estradiol.

3. Physiological stress and telogen effluvium: the delayed "shock"

This is probably one of the most common mechanisms when the shedding is sudden, diffuse, and dramatic.

A major stressor can push a large number of follicles into the resting phase. The consequence is not immediate: shedding often appears 2 to 3 months later, sometimes longer.

Common triggers include:

• Infection or fever

• Surgery

• Childbirth

• Rapid weight loss

• Under-eating

• Major emotional stress

• Physical or mental overwork

• Certain medications

What you may notice: diffuse shedding, often in handfuls, even though the hair previously seemed normal.

This can be very distressing, but the good news is that this type of hair loss is often reversible, provided the trigger is identified and the underlying terrain is corrected.

4. Inflammation, metabolic health, and insulin

The follicle does not exist in isolation. It is influenced by the broader terrain: low-grade inflammation, insulin resistance, androgen excess, and metabolic dysfunction.

In some women, especially in the context of PCOS or hyperandrogenism, insulin may indirectly contribute to the problem by promoting increased androgen production. In both men and women, metabolic dysfunction can also aggravate an inflammatory terrain that is already unfavorable to the follicle.

Metabolic health can be part of the picture, especially when it overlaps with hormonal or inflammatory factors.

Useful biomarkers: fasting glucose, fasting insulin, HbA1c, high-sensitivity CRP.

5. Scalp disorders, autoimmune forms, and scarring hair loss

Not all hair loss is related to deficiencies or hormonal imbalance.

Some cases require prompt dermatological evaluation:

• Alopecia areata: round or oval well-defined patches, often autoimmune in origin

• Frontal fibrosing alopecia: progressive recession of the frontal hairline, sometimes with eyebrow loss

• Seborrheic dermatitis, psoriasis, fungal infections: scaling, itching, local inflammation

These situations should not be minimized and require dermatological consultation.

Age and genetics also play a role in hair health. They influence follicle sensitivity, the rate of miniaturization, and the likelihood of developing certain forms of progressive hair loss, particularly androgenetic alopecia. But even here, predisposition does not mean inevitability: identifying the underlying terrain early often allows for more effective action.

Losing your hair can be very destabilizing. It can affect self-image, confidence, and sometimes even social life. But one essential point is worth remembering: hair loss is often an early signal. In other words: the earlier the cause is identified, the more options there are to act.

Which biomarkers can help us understand what is going on?

At Lucis, we analyze more than 100 biomarkers, several of which can help clarify hair loss depending on the context:

• Iron status: ferritin, iron, transferrin saturation

• Thyroid: TSH, free T4, free T3, antibodies

• Hormones: testosterone, SHBG, DHEA-S, and in some cases female hormones

• Inflammation: high-sensitivity CRP

• Metabolism: glucose, insulin, HbA1c

• Micronutrients: vitamin D, B12, folate, zinc

The goal is to understand the terrain, so that we can act with more precision, in a more personalized way, and avoid generic solutions.

To go further listen to our special episode on hair loss on the Lucis podcast

With Jonathan Encaoua, founder of Oma & Me (a brand specializing in hair health), we decode the real causes of hair loss in both men and women, the myths we still hear everywhere, and the concrete steps to take BEFORE it's too late.

The information contained in this article is provided for educational purposes only and does not constitute medical advice. It does not replace consultation with a qualified healthcare professional. In the case of significant, sudden, localized, or persistent hair loss, medical or dermatological advice is recommended.

References

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3. Fabbrocini G, Cantelli M, Masara A, et al. Female pattern hair loss: A clinical, pathophysiologic, and therapeutic review. Int J Womens Dermatol. 2018;4(4):203-211.

4. Grymowicz M, Rudnicka E, Podfigurna A, et al. Hormonal Effects on Hair Follicles. Int J Mol Sci. 2020;21(15):5342.

5. Harwood JM, Chakmakjian M, Kroumpouzos G. Female Pattern Hair Loss and Polycystic Ovary Syndrome: A Review. Skin Appendage Disord. 2023;9(1):1-7.

6. National Institute on Aging. How Stress Causes Hair Loss. 2023.

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8. Phillips TG, Slomiany WP, Allison R. Hair Loss: Common Causes and Treatment. Am Fam Physician. 2017;96(6):371-378.

9. Rossi A, Bellisario M, Dario V, et al. Postpartum Telogen Effluvium: Literature Review and Clinical Study in a Cohort of Women. Int J Womens Health. 2024;16:175-186.

10. Trost LB, Bergfeld WF, Calogeras E. The diagnosis and treatment of iron deficiency and its potential relationship to hair loss. J Am Acad Dermatol. 2006;54(5):824-844.