As a dermatologist and Stanford professor, Anne Lynn S. Chang has scientifically shaped the interface of skin, aging, and hormones – thereby highlighting how delicately the skin-hair-hormone system is regulated. Sudden hair loss appears dramatic, yet it is often a biological signal, not a destiny. Those who understand the hormonal triggers can quickly redirect the focus towards regeneration – for health, performance, and peace of mind.

Sudden diffuse hair loss is medically termed Telogen effluviumincreased transition of many hairs simultaneously into the resting phase (Telogen) followed by shedding. Common triggers are often hormonal and metabolic stressors: thyroid hormones regulate the timing of the hair cycle, Cortisolstress hormone from the adrenal gland affects the hair root, and Melatoninsleep-associated hormone with antioxidant effects on hair follicles modulates growth phases. In women, PCOSpolycystic ovary syndrome; a combination of hyperandrogenism, menstrual disturbances, and often insulin resistance can increase androgen effects, making the hair follicle more sensitive. Crash diets deprive the highly active hair matrix tissue of energy and micronutrients. The result: Many follicles collectively shut down – a few weeks later, the “shedding” occurs.

For high performers, this is more than a cosmetic issue. Increased chronic stress can shift cortisol patterns; measurable cortisol in hair samples reflects longer-term stress and correlates with stress-related assessments ^[1]. This hormonal imbalance promotes hair loss and reduces sleep quality and regeneration – a triple hit for energy, focus, and training adaptation. Restrictive diets with rapid weight loss classically trigger telogen effluvium; in clinical observations, affected individuals experienced clumps of hair loss within two to five months after starting the diet, with telogen rates reaching up to 50% – regrowth only occurred after re-nourishment ^[2]. Sleep deprivation weakens the melatonin-regulated stability of the hair cycle; human studies suggest benefits of topical melatonin solutions for density and shaft thickness ^[3], while foundational research shows the role of melatonin as an antioxidant regulator of the anagen phase ^[4]. Environmental toxins can also act as inflammatory and endocrine disruptors – from fine particulate matter to polycyclic compounds and heavy metals – thereby destabilizing scalp biology ^[5].

Stress and cortisol: In a field study involving employees, mobile stress assessments were compared with hair cortisol over 12 weeks. The correlation to common questionnaires was low; however, the relationship between hair cortisol and the assessment of stressful life events was significant ^[1]. Relevance: Not every subjective stress leaves the same biochemical trace – the cognitive assessment appears crucial. In practice, this means cause-oriented stress management rather than merely "symptom relaxation."

Crash diets and telogen effluvium: A case series documented massive hair loss two to five months after strict calorie restrictions resulting in weight loss of 12–25 kg; telogen rates increased to 25–50%, with hair regrowing after nutritional normalization ^[2]. Key message: The hair matrix is a high-energy tissue. Deficiencies trigger shutdown – reversible if the supply is restored.

Melatonin and hair growth: A systematic review identified 11 human studies, most of which showed improvements in growth, density, and shaft thickness after 3–6 months of daily topical melatonin application, especially in androgenetic alopecia ^[3]. Mechanistically, a current review supports the role of melatonin as an antioxidant and cycle-regulating factor for follicles, incorporating Wnt/BMP signaling ^[4]. Relevance: Sleep hygiene and targeted topical applications can support anagen stability.

- Prioritize medical evaluation: Have TSH, fT4/fT3, and antibodies (if suspected) checked; also check androgens, menstrual patterns, and metabolic markers in women to exclude or manage PCOS ^[6]. Early diagnosis creates room for intervention.
- Correct dietary strategy: Avoid crash diets. Plan for moderate weight loss (about 0.5–1% body weight/week), 1.6–2.2 g protein/kg/day, sufficient carbohydrates around training, and micronutrient density (iron, zinc, biotin, vitamin D as necessary clarification). This protects the hair matrix from telogen effluvium induced by energy deficits ^[2].
- Sleep as a growth factor: Prioritize 7–9 hours of consistent sleep. Darkness in the evening, cool room temperature, fixed times. Data suggest benefits of topical melatonin solutions (0.0033–0.1% once daily over 3–6 months) for follicle support; consult a doctor, especially in combined therapy ^{[3] [4]}.
- Address stress causally: Identify stressors with a brief daily reflection (What triggered it? What is within my control?). Combine stress reduction (delegation, meeting hygiene) with evidence-based recovery windows (e.g., 10-minute breathing focus after intense blocks). The goal: stabilize cortisol daily profiles rather than just “downregulating” ^[1].
- Minimize environmental exposure: In the city: wear head coverings in high UV/fine particulate matter exposure, conduct gentle evening scalp cleansing, and regularly ventilate/filter living spaces. Actively manage occupational exposures (solvents, pesticides): implement protective measures and, if possible, reduce exposures – to protect hormonal balance and scalp health ^[5].

The future of hair medicine will be more personalized: Biomarkers such as hair cortisol, digital stress trackers, and precise hormone profiles will guide therapeutic pathways. Expect combined approaches from endocrinological fine-tuning, chronobiology, and environmental medical protection – ensuring that hair not only regrows but also remains resilient.