Three Types of Hair Loss, Three Different Biomarker Stories
Walk into a pharmacy and the hair loss aisle will offer you biotin capsules, keratin-enriched shampoos, scalp serums, and collagen powders. Walk into a GP surgery in Germany and you are likely to leave with a reassurance that your blood work "looks fine." Neither response addresses the most common reason diffuse hair shedding escalates over months: something in your blood changed before your hair did.
Hair loss affects an estimated 50% of women by the age of 50 [1]. The causes are not mysterious. They are biological, they are measurable, and, critically, many of them are correctable if caught early enough. But "caught early" requires testing the right markers. And the markers that matter most for hair loss are rarely the ones your Hausarzt orders by default.
Before the biomarkers, it helps to understand which type of hair loss is in play. The three most clinically relevant are telogen effluvium, female pattern hair loss (androgenetic alopecia), and alopecia areata. Each has a different biological fingerprint, and each points to a different set of blood markers to investigate.
Telogen Effluvium, When Stress Tells Follicles to Stop
Hair follicles cycle between growth (anagen), transition (catagen), and rest (telogen) phases. Normally, roughly 85 to 90% of follicles are in anagen at any time. Telogen effluvium occurs when a physiological trigger pushes an abnormal proportion of follicles into the resting phase simultaneously. Those triggers include nutritional depletion, hormonal shift, systemic illness, and acute psychological stress. Three months later, they shed en masse. That three-month lag is why patients are often baffled: they had their stressful event or their surgery, felt fine for a while, and then suddenly their pillow was covered in hair.
This lag also matters diagnostically: you are testing for the nutritional state of three months ago, not today. Iron stores, thyroid status, and vitamin D levels at the time of the trigger are what caused the effluvium, which is why a single "normal" test result taken months later can miss the problem entirely.
Female Pattern Hair Loss, the Androgenic Side
Female pattern hair loss (FPHL, also called androgenetic alopecia) involves gradual miniaturisation of hair follicles driven by dihydrotestosterone (DHT), a metabolite of testosterone. Unlike telogen effluvium, which typically causes diffuse all-over shedding with a positive pull test, FPHL tends to produce widening at the parting with preserved frontal hairline, the "Christmas tree" pattern on dermoscopy.
The biomarker picture here involves androgens: free testosterone, SHBG, DHEA-S, and occasionally prolactin. A 2023 study of 155 female patients with alopecia found that nutritional deficiencies frequently co-existed with androgenic causes, with iron deficiency accounting for 70.3% of cases and zinc deficiency for 39.4% [2]. The two pathways are not mutually exclusive. Iron-depleted follicles are more vulnerable to androgen-mediated miniaturisation. Testing one without the other gives you half a picture.
Alopecia Areata, the Autoimmune Thread
Alopecia areata is an autoimmune condition in which the immune system attacks hair follicles, producing patchy, well-defined areas of hair loss rather than diffuse thinning. It is strongly associated with other autoimmune conditions, particularly autoimmune thyroid disease. Studies consistently find elevated thyroid antibodies (TPO-Ab, Tg-Ab) in alopecia areata patients at rates significantly higher than in controls [3]. Testing for Hashimoto's is therefore clinically relevant whenever alopecia areata is suspected, even if TSH is within range.
If you are experiencing hair shedding and want to understand why, the investigation starts with blood work, not with the supplement aisle. Aniva's comprehensive panel includes ferritin, the full iron panel, thyroid markers with antibodies, vitamin D, zinc, SHBG, testosterone, and hs-CRP, the complete set of markers that dermatologists and trichologists actually use to investigate hair loss. Get started with Aniva →
Ferritin: The Most Consistently Linked Marker
If there is one biomarker that appears in virtually every study of diffuse hair loss in women, it is ferritin. Not haemoglobin. Not serum iron. Ferritin, the protein that stores iron in your tissues and releases it when the body needs it.
A 2020 study comparing 54 patients with diffuse nonscarring hair loss against 55 healthy controls found mean ferritin levels of 14.72 ng/mL in the hair loss group versus 25.30 ng/mL in controls, a statistically significant difference (p<0.001) [4]. A 2025 case-control study of 200 women replicated this finding, showing ferritin as an independent predictor of hair loss even after adjusting for confounders [5]. The pattern is consistent across decades of research: hair loss patients have lower ferritin. Not always severely low, often just below the threshold the follicle needs to function optimally.
Why Ferritin Falls Before Haemoglobin Does
The body treats blood supply as a higher priority than hair. When iron stores begin to deplete, the body maintains haemoglobin levels, the oxygen-carrying molecule in red blood cells, by pulling from ferritin reserves. Hair follicles, being metabolically demanding but physiologically non-essential, are among the first tissues to receive reduced iron supply. The result: a patient with perfectly normal haemoglobin and a "normal" blood count (großes Blutbild) can simultaneously have ferritin stores so low that follicles are struggling to sustain the anagen phase. Our full article on iron and ferritin covers this hierarchy in depth.
This is why the großes Blutbild, which tests haemoglobin but not ferritin, is the wrong test if hair loss is your concern. It will reassure you that you are not clinically anaemic. It will tell you nothing about whether your iron stores can support your hair growth cycle.
What "Normal" Ferritin Looks Like on a Lab Report (and Why It Isn't Enough)
The lower end of the laboratory reference range for ferritin is typically 12 to 15 µg/L in most European labs. Clinically, this is the threshold below which frank iron deficiency anaemia begins to develop. It is emphatically not the threshold at which hair follicles function optimally.
In trichology practice, ferritin below 30 µg/L is increasingly considered concerning for hair loss, and the functional optimum for hair follicle health is generally cited as 50 to 70 µg/L or above [6]. A patient with a ferritin of 16 µg/L will be told her iron is "within normal range." A trichologist will tell her something different.
There is an additional complication: ferritin is an acute-phase reactant. During active inflammation or infection, ferritin levels rise regardless of actual iron stores. A patient with genuine iron depletion and concurrent inflammation may show a falsely normal ferritin. This is why testing ferritin alongside hs-CRP provides a more accurate picture. High ferritin with high CRP warrants more investigation, not reassurance.
The French RCT That Changed the Conversation
A randomised controlled trial published in the Canadian Medical Association Journal tested iron supplementation in non-anaemic women with ferritin below 41 µg/L and persistent fatigue. After 12 weeks, the iron group showed a 47.7% reduction in fatigue scores compared to placebo [7]. These were women with "normal" haemoglobin, women who would have been told by any standard blood test that their iron was fine.
The hair implications are direct: if iron below 41 µg/L is sufficient to drive significant fatigue in non-anaemic women, it is also sufficient to compromise the energetically demanding process of hair follicle cycling. The tissue most sensitive to marginal iron depletion is not always the one showing symptoms.
Thyroid Hormones: TSH Alone Won't Tell You Enough
The relationship between thyroid dysfunction and hair loss is well established and operates through multiple pathways. Thyroid hormones directly regulate the anagen phase of the hair cycle: triiodothyronine (T3) prolongs anagen and stimulates keratinocyte proliferation in the hair matrix, while hypothyroidism shortens it [8]. Both underactive and overactive thyroid states can cause hair loss. Hypothyroidism typically produces diffuse thinning across the scalp including the lateral eyebrows, while hyperthyroidism causes finer, more fragile hair with accelerated shedding.
The diagnostic complication is that subclinical thyroid dysfunction, the stage where TSH is at the high or low end of the normal range but not yet outside it, can be sufficient to affect hair cycling while remaining invisible on a screening TSH alone.
The Case for Testing Free T3, Free T4, and Antibodies
TSH is a pituitary hormone, not a thyroid hormone. It tells you how hard the pituitary is pushing the thyroid to produce hormones. It does not tell you whether the thyroid is converting T4 to the active form T3 efficiently, nor whether autoimmune thyroid disease is developing beneath a still-normal TSH reading.
Autoimmune thyroiditis (Hashimoto's disease) is particularly relevant for hair loss patients. Hashimoto's can cause episodic thyroid inflammation with fluctuating hormone levels that produce hair loss during the inflammatory phases while TSH remains intermittently normal. The only reliable way to identify it early is to measure TPO antibodies (anti-thyroid peroxidase) and Tg antibodies (anti-thyroglobulin). In the population of women presenting with diffuse hair loss, identifying subclinical Hashimoto's, before overt hypothyroidism develops, is one of the most clinically useful things a comprehensive panel can do.
The standard thyroid check ordered in response to hair loss complaints, a single TSH, will miss impaired T4-to-T3 conversion and will miss early autoimmune thyroiditis. Full thyroid assessment means TSH, free T4, free T3, and antibodies.
Testing the full thyroid panel costs almost nothing extra relative to TSH alone, but it provides a categorically different quality of information. Aniva's panel includes TSH, free T4, free T3, TPO-Ab, and Tg-Ab as standard. Start your membership →
Vitamin D: A Receptor in Every Hair Follicle
Vitamin D receptors (VDRs) are expressed in keratinocytes throughout the hair follicle. This is not a peripheral observation. It suggests a direct regulatory role for vitamin D in follicle cycling. Mice with deleted VDR genes develop alopecia despite normal circulating vitamin D levels, which indicates that the receptor itself matters, not just the ligand. In humans, the evidence linking low vitamin D to non-scarring alopecia is consistent across multiple studies, even if causality remains to be fully established.
The same 2020 study that found significantly lower ferritin in hair loss patients also found significantly lower 25-hydroxyvitamin D: mean 14.03 ng/mL in hair loss patients versus 17.01 ng/mL in controls (p=0.01) [4]. The 2025 case-control study replicated this, showing vitamin D as an independent predictor of hair loss in the multivariate model [5].
Why Northern Europeans Are Disproportionately Affected
In Germany and Finland, the sun angle between October and March is insufficient for meaningful cutaneous vitamin D synthesis. The Robert Koch Institut's DEGS study found that approximately 56% of adults in Germany have 25-hydroxyvitamin D levels below 50 nmol/L, the threshold below which most researchers consider supplementation clinically warranted [9]. For a woman with diffuse hair loss presenting in spring after a Northern European winter, low vitamin D should be on the differential before any other explanation is reached for. It is ubiquitous, it is measurable, and it is correctable. Our detailed analysis of vitamin D in Northern Europe covers the broader deficiency data.
One important nuance: the hair loss literature uses ng/mL while many European labs report nmol/L. The conversion factor is 2.5 (40 nmol/L = 16 ng/mL). The hair loss study cut-offs, typically 20 to 30 ng/mL, correspond to 50 to 75 nmol/L. Supplementing vitamin D without testing first means guessing at a dose. The only way to know where you are, and where you need to get to, is to measure.
Zinc, Selenium, and the Cu/Zn Ratio
The role of zinc in hair health is mechanistically well supported: zinc acts as a cofactor in enzymes involved in keratin synthesis, inhibits hair follicle regression, and supports sebaceous gland function. Severe zinc deficiency produces dramatic hair loss among its hallmark features, as seen in acrodermatitis enteropathica, a rare genetic disorder of zinc absorption [10].
The question is whether more modest zinc depletion, common in European dietary patterns, is sufficient to contribute to non-severe hair shedding. The evidence is mixed. A 2024 retrospective study of zinc testing in hair loss patients found that hair loss patients had statistically but not clinically significantly lower zinc levels than controls [11]. Routine zinc testing for every hair loss patient is not universally recommended. Testing is most useful when there are additional risk factors: vegetarian or vegan diet, restrictive eating history, or a dietary pattern low in red meat and shellfish.
The Copper/Zinc Ratio as a Diagnostic Marker
More interesting than absolute zinc alone is the copper-to-zinc ratio. A 2024 case-control study of 90 women with chronic telogen effluvium found the Cu/Zn ratio to be a statistically significant predictor of chronic TE diagnosis, while neither copper nor zinc alone reached significance [12]. This makes physiological sense: zinc and copper compete for absorption, and the balance between them, rather than either in isolation, reflects the functional mineral status of the body.
This has a direct implication for supplementation. Taking high-dose zinc without monitoring copper can deplete copper over time, potentially creating a deficiency that worsens the very condition you are trying to address. Testing both, and evaluating the ratio, prevents this. It is a good example of why single-marker testing misses what panel-based testing catches.
Selenium
Selenium deficiency has been associated with hair loss in animal models and small human studies, with the 2025 case-control study finding lower selenium as an independent predictor of hair loss in multivariate regression [5]. Selenium is also required for glutathione peroxidase activity, the enzyme that protects follicle cells from oxidative damage. Like zinc, selenium excess can also cause hair loss (selenosis), making the testing-before-supplementing principle particularly relevant here.
Sex Hormones: SHBG, Testosterone, and Androgens
In women with female pattern hair loss, the relevant hormonal markers are those related to androgen availability: total and free testosterone, DHEA-S (adrenal androgen), and SHBG. It is not always the absolute level of androgens that matters. What counts is whether those androgens are biologically available to hair follicle receptors, and that availability is governed by SHBG.
The SHBG Effect
Sex hormone binding globulin binds to testosterone (and oestradiol), rendering it biologically inactive. When SHBG is low, free testosterone rises, meaning even modest total testosterone levels can drive androgenic hair loss if SHBG is suppressed. What suppresses SHBG? Caloric restriction, aggressive intermittent fasting, elevated insulin, liver stress, and hypothyroidism. Chronic cortisol elevation also plays a role through its effects on insulin sensitivity and, downstream, SHBG.
The clinical implication is that a woman on a restrictive diet, experiencing high stress, and presenting with diffuse hair loss may have "normal" total testosterone, and still have elevated free testosterone driving FPHL because her SHBG has been suppressed. Testing total testosterone without SHBG gives you half the picture and may miss the driver entirely.
Hair loss that has been dismissed because "your hormones look fine" may simply mean the wrong hormones were tested. Free testosterone and SHBG together tell a fundamentally different story than total testosterone alone. See the full Aniva biomarker panel →
Inflammation as a Root Cause: hs-CRP
Chronic low-grade inflammation disrupts the hair growth cycle through multiple pathways: it can trigger premature telogen entry, damage follicle stem cells, and, when associated with autoimmune activity, directly target follicle structures. High-sensitivity C-reactive protein (hs-CRP) is the practical clinical marker for systemic inflammatory load.
Elevated hs-CRP is also clinically relevant for interpreting ferritin results, as noted above. A high ferritin in the context of high hs-CRP indicates inflammation rather than iron sufficiency. Running both markers together is essential for accurate interpretation.
Beyond its role in hair specifically, hs-CRP above 3 mg/L warrants investigation of its cause, whether that is metabolic dysfunction, gut issues, or an undiagnosed autoimmune condition that may itself be contributing to the alopecia.
The Practical Panel: What to Actually Request
A GP visit for hair loss in Germany will typically result in a großes Blutbild. That checks haemoglobin and white blood cell differentials. For hair loss specifically, this tells you almost nothing useful. What a dermatologist or trichologist would actually want to see is:
Iron status: Ferritin (the single most important marker), serum iron, transferrin saturation. Not haemoglobin alone.
Thyroid: TSH, free T4, free T3, TPO antibodies, and Tg antibodies. Not TSH alone.
Nutritional markers: 25-hydroxyvitamin D, zinc, selenium, vitamin B12 (B12 deficiency can co-occur with iron deficiency, particularly in vegetarians). Folate if indicated.
Hormonal assessment (for pattern hair loss): Total testosterone, free testosterone (calculated from SHBG), SHBG, DHEA-S. In women with suspected PCOS, also LH and FSH.
Inflammation: hs-CRP. Provides context for ferritin interpretation and flags systemic inflammation as a contributing factor.
This is not an exotic or expensive panel. It is the standard workup that hair loss specialists use. The challenge is that it is not what the German statutory health system orders by default. As we have written in detail about the großes Blutbild, there is a substantial gap between what the Krankenkasse funds and what comprehensive preventive testing actually requires.
What Good Results Look Like (and When They Don't)
It is worth stating clearly what you are trying to achieve with this testing, because "within the reference range" is not the goal. The targets most relevant to hair health:
Ferritin: Above 50 µg/L is typically cited as the functional optimum for follicle health. Between 30 and 50 µg/L is a grey zone. Below 30 µg/L is strongly associated with effluvium in the literature, regardless of haemoglobin status.
Vitamin D: 75 to 150 nmol/L (30 to 60 ng/mL) is the range most evidence supports for optimal tissue function. The standard "sufficient" threshold of 50 nmol/L represents the minimum, not the target.
TSH: Most thyroid specialists consider 1.0 to 2.5 mIU/L as functionally optimal. Many laboratories report up to 4.0 mIU/L as normal. The upper end of this range is associated with subclinical hypothyroidism in symptomatic patients.
Zinc: The reference range lower limit for serum zinc is typically 60 to 70 µg/dL in European labs. Values in the lower third of this range, particularly combined with elevated Cu/Zn ratio, are clinically relevant for hair loss even if technically "normal."
One blood draw. One panel. A complete picture of the biological variables that actually govern hair follicle function, rather than another bottle of biotin. Aniva's annual membership covers all of these markers at €199/year, at an ISO 15189-certified German laboratory, with a personalised report explaining what your results mean for your health. Begin your membership →
Key Takeaways
Diffuse hair loss has biological causes that are measurable in blood. The großes Blutbild, the default test for most German patients, checks none of the markers most relevant to hair loss. Ferritin is consistently the most important marker. The functional optimum (50+ µg/L) is far higher than the laboratory lower limit of normal (~12 to 15 µg/L). Thyroid assessment requires TSH plus free T4, free T3, and antibodies, because TSH alone misses Hashimoto's and impaired T4-to-T3 conversion. Vitamin D below 50 nmol/L is endemic in Northern Europe and directly affects follicle cycling via vitamin D receptors in the hair matrix. SHBG and free testosterone together reveal androgenic hair loss drivers that total testosterone alone misses. Inflammation (hs-CRP) is both a potential driver of hair loss and an essential context marker for accurate ferritin interpretation.
The supplement industry has made hair loss feel like a deficiency of biotin and collagen. The research suggests it is more often a deficiency of iron, vitamin D, and, frequently, adequate investigation.
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Sources
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2. Lin CS, Chan LY, Wang JH, Chang CH. "Diagnosis and treatment of female alopecia: Focusing on the iron deficiency-related alopecia." Tzu Chi Medical Journal. 2023. PMC10683524
3. Thyroid autoantibodies and alopecia areata, clinical summary. HairGP.co.uk. 2025. Source
4. Güder H et al. "Serum ferritin and vitamin D levels should be evaluated in patients with diffuse hair loss prior to treatment." Advances in Dermatology and Allergology. 2020. PMC7394174
5. Sharaf et al. "Quantitative Analysis of Selected Circulating Hematological Biomarkers in Females Affected by Hair Loss." Diseases. 2025;13(11):352. MDPI
6. Zhang D, LaSenna C, Shields BE. "Serum Ferritin Levels: A Clinical Guide in Patients with Hair Loss." Cutis. 2023. Source
7. Vaucher P et al. "Effect of iron supplementation on fatigue in nonanemic menstruating women with low ferritin." CMAJ. 2012;184(11):1247-1254. PubMed
8. van Beek N et al. "Thyroid hormones directly alter human hair follicle functions." Journal of Clinical Endocrinology & Metabolism. 2008. PubMed
9. Rabenberg M et al. "Vitamin D status among adults in Germany, results from the German Health Interview and Examination Survey for Adults (DEGS1)." BMC Public Health. 2015;15:641. PMC4530987
10. Guo EL, Katta R. "Diet and hair loss: effects of nutrient deficiency and supplement use." Dermatology Practical and Conceptual. 2017. PubMed
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12. Türkoğlu IN et al. "A comprehensive investigation of biochemical status in patients with telogen effluvium." Journal of Cosmetic Dermatology. 2024;23(12):4277-4284. PMC11626366
This content is for informational purposes only and is not medical advice. Hair loss has multiple potential causes, including genetic, hormonal, and medical conditions that require assessment by a qualified dermatologist or physician. Blood test results should always be interpreted in the context of your individual health history and clinical picture. Always discuss symptoms and test results with a qualified healthcare professional before making changes to supplementation or treatment.
