Hair Loss: Symptoms, Causes, Diagnostic Tests, and Treatment

Hair loss is one of the most common reasons for visiting a dermatologist or primary care physician, as it can significantly affect both an individual's appearance and psychological well-being. Although losing approximately 50 to 100 hairs per day is a normal part of the natural hair growth cycle, excessive or prolonged hair shedding may indicate an underlying condition that requires further investigation.

Hair loss is not a disease in itself but rather a clinical symptom with a multifactorial etiology. It may be associated with genetic factors, hormonal changes, nutritional deficiencies, chronic psychological or physical stress, autoimmune diseases, endocrine disorders, medications, or other pathological conditions. Identifying the underlying cause is essential, as different mechanisms require different therapeutic approaches.

The modern evaluation of hair loss is not limited to examining the scalp alone. Instead, it involves assessing the individual's overall health in order to identify potential metabolic, hormonal, inflammatory, and nutritional factors that may disrupt the normal hair growth cycle. For this reason, appropriate laboratory testing is a fundamental tool for personalized diagnosis and targeted management.

Epidemiology

Hair loss is one of the most common scalp disorders worldwide, affecting millions of people regardless of age or sex. Its prevalence depends on the underlying cause, age, sex, genetic predisposition, and the presence of coexisting medical conditions. While some forms of hair loss are temporary and reversible, others follow a chronic course and require long-term monitoring.

The most common form of hair loss is androgenetic alopecia. It is estimated to affect approximately 30% of men by the age of 30, 50% by the age of 50, and more than 70% at older ages. Although it occurs more frequently in men, a significant proportion of women also develop female pattern androgenetic alopecia, particularly after menopause, when hormonal changes become more pronounced.

Diffuse hair loss (telogen effluvium) is also a very common condition. It typically occurs several months after a significant physiological or psychological stressor, such as a severe infection, surgery, pregnancy, rapid weight loss, or marked nutritional deficiencies. The increased incidence observed following the COVID-19 pandemic highlighted the important role of systemic inflammatory stress in disrupting the normal hair growth cycle.

Alopecia areata is considerably less common, with an estimated lifetime risk of approximately 2%. It is an autoimmune disease that can occur at any age and is characterized by sudden, localized hair loss. In more severe cases, it may extend to involve the entire scalp or even the whole body.

In Greece, there are no large-scale epidemiological studies that accurately document the prevalence of all forms of hair loss in the general population. Nevertheless, clinical experience and available data from Greek dermatology clinics indicate that androgenetic alopecia is the leading cause of chronic hair loss, whereas telogen effluvium is particularly common among women of reproductive age, especially in the presence of iron deficiency, thyroid disorders, significant psychological stress, or strict calorie-restricted diets.

In recent years, an increasing number of studies have emphasized that hair loss often reflects broader disturbances in overall health. Consequently, the timely and comprehensive investigation of potential metabolic, hormonal, inflammatory, and nutritional factors may contribute not only to improving hair health but also to identifying underlying disorders that might otherwise remain undiagnosed.

Symptoms and Signs

Hair loss may present in different forms, with varying severity and patterns of progression, depending on the underlying cause. In some cases, it develops gradually over several years, whereas in others the onset is sudden and the hair loss is particularly severe.

Careful evaluation of the pattern of onset, distribution, and associated symptoms provides valuable diagnostic information. The most common symptoms and clinical signs include:

Increased hair shedding during washing or brushing. This is one of the earliest signs noticed by most patients. When excessive shedding persists for several weeks or progressively worsens, it may indicate a disturbance of the normal hair growth cycle.
Reduced hair density. Hair thinning is usually first noticed on the crown, along the central parting, or at the temples. In women, the reduction in hair density is often diffuse, whereas in men it typically follows the characteristic pattern of recession of the frontal hairline together with thinning at the vertex.
Hair shaft miniaturization. Newly growing hairs become thinner and have a smaller diameter than normal hairs. This is a hallmark of androgenetic alopecia and reflects the progressive miniaturization of hair follicles.
Localized hairless patches. The sudden appearance of round or oval areas without hair is characteristic of alopecia areata. The skin in these areas is usually normal, without scarring or visible inflammation.
Changes in hair quality. Hair may become more brittle, dry, dull, or prone to breakage. Although these findings do not always represent true hair loss, they frequently coexist with nutritional deficiencies or metabolic disorders.
Increased hair loss affecting the entire body. In some cases, hair loss is not confined to the scalp but also involves the eyebrows, eyelashes, or other areas of the body. This presentation may be associated with autoimmune diseases, severe systemic illnesses, or medication use.

In addition to hair loss, many patients experience scalp-related symptoms such as itching, a burning sensation, tenderness, or increased oiliness. Although these symptoms are not present in all forms of hair loss, when they do occur they may suggest inflammatory or dermatological conditions, such as seborrheic dermatitis or psoriasis.

Hair loss is also frequently accompanied by signs and symptoms affecting the entire body. Fatigue, reduced exercise tolerance, brittle nails, pallor, menstrual irregularities, changes in body weight, intolerance to cold or heat, and mood changes may all point toward nutritional deficiencies, thyroid disorders, hormonal imbalances, or other systemic diseases.

A thorough assessment of all symptoms, together with the patient's medical history, physical examination, and appropriate laboratory investigations, is the most important step in identifying the true cause of hair loss and selecting the most appropriate therapeutic approach.

Underlying Causes of Hair Loss

Hair loss is the final consequence of disruption of the normal hair growth cycle. Under normal conditions, hair follicles progress through successive phases of growth, transition, and rest. When this balance is disturbed by internal or external factors, a greater number of hair follicles prematurely enter the shedding phase, or their ability to produce new healthy hairs is reduced.

In most cases, more than one etiological factor is involved, making a comprehensive laboratory evaluation essential rather than focusing solely on treating the symptom itself.

Genetic Predisposition and Androgenetic Alopecia
Androgenetic alopecia is the most common cause of chronic hair loss in both men and women. It results from the combination of genetic predisposition and increased sensitivity of hair follicles to dihydrotestosterone (DHT), an active metabolite of testosterone. Over time, hair follicles gradually shrink (miniaturize), producing progressively finer and shorter-lived hairs until they eventually become inactive. However, genetic predisposition alone does not determine the age of onset or the rate of progression of hair loss. Hormonal imbalances, nutritional deficiencies, chronic inflammation, oxidative stress, and other environmental factors may significantly influence disease progression, highlighting the importance of an individualized clinical and laboratory evaluation.

Nutritional Deficiencies
Normal hair growth requires an adequate intake of protein, iron, zinc, selenium, biotin (vitamin B7), vitamin D, vitamin B12, folate, and other essential micronutrients. Inadequate intake, malabsorption, or increased physiological requirements can impair hair follicle function and lead to diffuse hair loss. Iron deficiency is one of the most common reversible causes, particularly in women of reproductive age.

Hormonal Disorders
Hormones directly influence the hair growth cycle. Thyroid disorders, adrenal dysfunction, polycystic ovary syndrome (PCOS), hormonal changes during pregnancy and the postpartum period, as well as the hormonal changes associated with menopause, can all lead to significant hair loss. In many women, hair loss is the first manifestation of an underlying endocrine disorder.

Chronic Inflammation and Oxidative Stress
In recent years, chronic low-grade inflammation has been recognized as an important factor affecting the normal function of hair follicles. Increased production of inflammatory cytokines and reactive oxygen species damages cells within the hair root, accelerating their transition into the shedding phase. Obesity, metabolic syndrome, chronic infections, and an unhealthy lifestyle are common sources of persistent inflammation.

Psychological and Physical Stress
Severe or prolonged stress is one of the most important triggers of telogen effluvium. Activation of the hypothalamic–pituitary–adrenal (HPA) axis and the resulting increase in cortisol production disrupt the normal hair growth cycle. Likewise, severe infections, major surgery, high fever, or significant trauma can lead to substantial hair shedding two to four months after the triggering event.

Autoimmune Diseases
In alopecia areata, the immune system mistakenly attacks the hair follicles, causing sudden hair loss in well-defined areas. Similar mechanisms may also be involved in other autoimmune diseases, such as Hashimoto's thyroiditis, systemic lupus erythematosus, and celiac disease, in which hair loss is a common associated finding.

Gastrointestinal Disorders and Nutrient Malabsorption
Proper gastrointestinal function is essential for the absorption of the nutrients required for healthy hair formation. Conditions such as celiac disease, inflammatory bowel disease, chronic gastritis, Helicobacter pylori infection, and disturbances of the gut microbiota may lead to vitamin and trace element deficiencies, even when dietary intake is adequate.

Medications and Medical Treatments
Many medications may cause hair loss as an adverse effect. These include certain anticancer drugs, anticoagulants, retinoids, antithyroid medications, antiepileptic drugs, beta-blockers, and some antidepressants. In most cases, hair loss is reversible after discontinuation or adjustment of the medication, always in consultation with the treating physician.

Rapid Weight Loss and Restrictive Diets
Very low-calorie diets, inadequate protein intake, and rapid weight loss are common causes of diffuse hair loss. When the body is in a state of energy deficiency, it prioritizes the distribution of nutrients to vital organs while reducing their supply to non-essential tissues such as the hair follicles, thereby preserving basic metabolic functions.

Environmental and Lifestyle Factors
Smoking, excessive alcohol consumption, chronic sleep deprivation, a sedentary lifestyle, increased exposure to air pollution, and frequent chemical or heat treatments applied to the hair may all impair hair follicle function. Although these factors are usually not the sole cause of hair loss, they often act synergistically with other contributing factors, accelerating disease progression.

Clinical and Laboratory Evaluation of Hair Loss

The evaluation of hair loss cannot rely on a single diagnostic test. Instead, it requires a combination of conventional and specialized laboratory investigations to identify the underlying biological mechanisms affecting the hair growth cycle. In androgenetic alopecia, genetic predisposition is assessed primarily through the patient's personal and family history, together with the clinical presentation. However, even when there is a clear genetic predisposition, investigating potentially modifiable factors, such as nutritional deficiencies, hormonal imbalances, and chronic inflammation, may help personalize the therapeutic approach. The selection of laboratory tests should therefore be individualized according to the patient's age, sex, medical history, associated symptoms, and overall clinical presentation.

(a) Specialized Dermatological Investigations
The diagnosis of hair loss usually begins with a clinical assessment by a dermatologist. The following investigations help determine the type of alopecia and exclude scalp disorders that require a different therapeutic approach.

Scalp dermoscopy (Trichoscopy): A non-invasive examination used to evaluate hair follicles and assist in the differential diagnosis of the various forms of alopecia.
Scalp skin biopsy: Performed in selected cases when scarring alopecia or rare dermatological disorders are suspected.
Hair Pull Test: A simple clinical test used to assess the degree of active hair shedding.
Phototrichogram: A quantitative method for evaluating hair density, growth rate, and hair shaft diameter.
Evaluation by a dermatologist specializing in scalp disorders: Contributes to a comprehensive clinical assessment and the accurate interpretation of laboratory findings.

(b) Conventional Laboratory Tests
Once the type of hair loss has been established, the basic laboratory work-up is performed to investigate common causes such as anemia, thyroid dysfunction, and iron deficiency. Specifically, the following tests may be recommended:

Complete Blood Count (CBC): Evaluates anemia, white blood cells, and platelets. Iron-deficiency anemia and other hematological disorders are common causes of diffuse hair loss.
Ferritin: The most reliable indicator of the body's iron stores. Even mildly reduced ferritin levels may be associated with increased hair shedding, particularly in women.
Serum Iron, TIBC, and Transferrin Saturation (%): These tests complement the assessment of iron metabolism and help distinguish true iron deficiency from functional iron deficiency.
TSH, Free T4 (FT4), and Free T3 (FT3): Assess thyroid function. Both hypothyroidism and hyperthyroidism may cause significant hair loss.

(c) Functional Medicine Testing
Functional Medicine testing complements conventional laboratory investigations by exploring the underlying biological mechanisms that may contribute to the development or persistence of hair loss.

Assessment of Nutritional Deficiencies
Identifying true nutritional deficiencies allows for targeted dietary and nutritional supplementation strategies.

Comprehensive Vitamin Assessment (NutriScan®): Evaluates the major water-soluble and fat-soluble vitamins, including B7 (biotin), B9 (folate), B12, A, C, D, and E, all of which play essential roles in keratin synthesis, cellular proliferation, and antioxidant protection of hair follicles.
Comprehensive Serum Trace Elements Profile (Metals&Traces®): Measures essential trace elements such as zinc, selenium, copper, iron, magnesium, and manganese, which are required for keratin synthesis, cellular growth, and the antioxidant defense of hair follicles.
MetaBolomiX™ Organic Acids Analysis (NutriScan®): Provides information on cellular metabolism, energy production, B-complex vitamin metabolism, and the body's antioxidant capacity. This test may reveal functional metabolic disturbances that indirectly affect the hair growth cycle.

Assessment of Hormonal Disorders and the Stress Axis
The HormoneScan® testing panel helps investigate hormonal imbalances, hyperandrogenism, and dysfunction of the hypothalamic–pituitary–adrenal (HPA) axis, all of which may contribute to hair loss. The most appropriate test is selected according to the patient's sex, age, and clinical presentation.

Comprehensive Thyroid Evaluation: Thyroid dysfunction is a common cause of diffuse hair loss. This assessment includes TSH, fT3, fT4, rT3, the fT3/rT3 ratio, and anti-TPO and anti-TG antibodies, allowing for a comprehensive evaluation of thyroid function and screening for autoimmune thyroiditis.
Adrenal Function Assessment (AdrenalScan®): Evaluates the daily cortisol profile and DHEA-S levels, providing insight into the function of the hypothalamic–pituitary–adrenal axis. It is particularly useful in patients with chronic hair loss accompanied by significant stress, fatigue, or sleep disturbances.
Basic Male Hormonal Assessment: Intended for men with hair loss and suspected hormonal abnormalities. It includes biomarkers such as testosterone, dihydrotestosterone (DHT), DHEA-S, and other hormones influencing hair follicle function, thereby contributing to the evaluation of androgenetic alopecia.
Comprehensive Menstrual Cycle Assessment (CycloScan®): Provides a detailed evaluation of hormonal fluctuations throughout the entire menstrual cycle. It is particularly useful in women with hair loss associated with menstrual irregularities, infertility, or suspected hormonal imbalance.
Comprehensive Menopause Assessment (MenoScan®): Evaluates the hormonal profile of women during the perimenopausal and menopausal periods, when changes in estrogen, progesterone, and androgen levels are common causes of progressive hair thinning.

Assessment of Chronic Inflammation and Oxidative Stress

Chronic Inflammation Assessment (ImmuneScan®): Includes biomarkers such as IL-1β, IL-6, IL-8, TNF-α, hs-CRP, and LPS, providing an evaluation of chronic low-grade inflammation. It is useful when persistent inflammatory burden is suspected to be affecting the hair growth cycle.
Oxidative Stress Assessment (DetoxScan®): Evaluates biomarkers of oxidative stress and antioxidant defense, contributing to the investigation of metabolic disturbances that may impair hair follicle function.

Assessment of Gut Microbiota Disorders

Gut Microbiota Assessment (EnteroScan®): Evaluates the composition of the gut microbiota and identifies dysbiosis. This test is useful in patients with chronic or unexplained hair loss, as gastrointestinal disturbances may impair nutrient absorption and immune function.

Assessment of Environmental and Toxic Exposures

Heavy Metals Assessment (Metals & Traces®): Chronic exposure to heavy metals such as mercury, lead, and arsenic may disrupt cellular metabolism and contribute to hair loss. This test is indicated when there is a relevant history of occupational or environmental exposure.

Therapeutic Approaches to Hair Loss

The choice of the most appropriate treatment depends on the type of hair loss and its underlying causes. For this reason, thorough clinical assessment and laboratory investigation should always precede treatment, ensuring that management is both targeted and individualized. In most cases, the combination of conventional medical therapies and evidence-based natural interventions yields the best outcomes.

(a) Conventional Treatments
The available conventional treatment options vary according to the type of hair loss and should be initiated only after appropriate medical evaluation.

Topical minoxidil: The most commonly used treatment for androgenetic alopecia in both men and women. It promotes hair growth and increases hair density. Initial results are usually observed after 3 to 6 months of continuous use. The most common adverse effects include mild scalp irritation, itching, and temporary increased hair shedding during the initial phase of treatment.
Finasteride and dutasteride: Primarily used in men with androgenetic alopecia. These medications work by reducing dihydrotestosterone (DHT) levels, a hormone involved in the progressive miniaturization of hair follicles. They may cause adverse effects such as decreased libido or erectile dysfunction in a small percentage of patients (see our detailed article on finasteride for more information). They are contraindicated during pregnancy, and finasteride is not recommended for women of reproductive age.
Antiandrogen therapy in women: Women with elevated androgen levels or polycystic ovary syndrome (PCOS) may be treated with medications such as spironolactone or certain hormonal contraceptives. Treatment should always be prescribed by the treating physician and requires regular monitoring.
Corticosteroids and immunomodulatory therapies: In alopecia areata, topical or intralesional corticosteroids may be used. In more severe cases, newer immunomodulatory therapies, such as JAK inhibitors, may be prescribed under the supervision of a specialist.
Platelet-Rich Plasma (PRP) and Hair Transplantation: Platelet-rich plasma (PRP) therapy is used in selected patients to enhance hair follicle function. Hair transplantation is a surgical option for individuals with stabilized androgenetic alopecia and can provide permanent restoration of hair growth when an adequate donor area is available.

(b) Natural Therapies
The primary goal of a natural approach to hair loss is to correct the underlying biological disturbances that impair hair follicle function. Unlike treatments that focus exclusively on reducing hair shedding, interventions involving lifestyle, nutrition, and dietary supplements aim to address the root causes, such as nutritional deficiencies, hormonal imbalances, chronic inflammation, increased oxidative stress, and gastrointestinal dysfunction. For this reason, the selection of appropriate interventions should be based on the findings of a comprehensive laboratory evaluation and individualized according to each patient's needs.

Nutrition
A balanced diet is a fundamental prerequisite for normal hair growth. Adequate intake of high-biological-value protein provides the amino acids required for keratin synthesis, while foods rich in iron, zinc, selenium, vitamin D, B-complex vitamins, and omega-3 fatty acids support normal hair follicle function. At the same time, adherence to the Mediterranean diet, characterized by a high intake of vegetables, fruits, legumes, nuts, fish, and extra virgin olive oil, contributes to reducing chronic inflammation and oxidative stress. In contrast, strict calorie-restricted diets and inadequate protein intake are common causes of worsening hair loss.

Lifestyle
Adequate sleep, regular physical activity, and effective management of chronic stress can significantly impact the hormonal and metabolic pathways that regulate the hair growth cycle. Smoking cessation, limiting excessive alcohol consumption, and avoiding frequent heat styling or chemical hair treatments also help preserve normal hair follicle function. In addition, appropriate management of coexisting conditions such as obesity, diabetes mellitus, and thyroid disorders is an essential component of the overall therapeutic strategy.

Dietary Supplements
Supplementation should always be based on documented laboratory deficiencies rather than empirical use.

Iron supplementation is recommended only when iron deficiency has been confirmed. The usual dosage ranges from 30–60 mg of elemental iron daily, preferably taken together with vitamin C to enhance absorption. Possible adverse effects include gastrointestinal discomfort and constipation, while supplementation is contraindicated in conditions associated with iron overload.
Vitamin D should be prescribed only in cases of confirmed deficiency, with dosage individualized according to 25-hydroxyvitamin D [25(OH)D] levels and the recommendations of the treating physician. Excessive supplementation may lead to hypercalcemia and other adverse effects.
Zinc supplementation is appropriate only when deficiency has been documented, typically at doses of 15–30 mg daily for a limited period. Long-term use of high doses may result in copper deficiency.
Vitamin B7 (biotin) does not appear to provide benefit in individuals with normal biotin levels but may be useful in the rare cases of true deficiency. Furthermore, high-dose biotin supplementation can interfere with the results of several immunoassays and should therefore be discontinued before laboratory testing according to the laboratory's recommendations.

Herbal Therapies
Several herbal preparations have been investigated as adjunctive treatments for androgenetic alopecia. Serenoa repens extract is the best studied, as it appears to exert mild inhibitory effects on 5-alpha-reductase activity. Although some studies have demonstrated modest benefit, the available evidence is insufficient for it to replace established medical therapies. Other botanical agents, such as rosemary oil, have also shown encouraging but limited scientific evidence and should be used only as complementary interventions following the recommendation of a healthcare professional.

The Importance of an Individualized Approach

Hair loss is a multifactorial disorder that often results from a combination of nutritional deficiencies, hormonal imbalances, chronic inflammation, increased oxidative stress, gut microbiota dysfunction, or other metabolic disturbances. Consequently, there is no single treatment that is effective for every patient.

The selection of the most appropriate therapeutic approach should be based on careful clinical assessment and comprehensive laboratory evaluation in order to identify the true underlying causes of hair loss and implement targeted interventions. An individualized approach increases the likelihood of meaningful and long-term improvement while avoiding unnecessary treatments or the empirical use of dietary supplements without documented indications.

References

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