Hair loss is one of the most emotionally distressing conditions a person can experience — yet it remains one of the most clinically underinvestigated. For most people, a GP visit results in a referral to a dermatologist or a prescription for minoxidil. What rarely happens is a systematic investigation of the underlying drivers: iron deficiency, thyroid dysfunction, hormonal imbalance, nutritional gaps, chronic stress, alcohol, and environmental triggers.
This article is for informational purposes only and does not constitute medical advice. Please consult a qualified healthcare professional for diagnosis and treatment.
Understanding Hair Biology: The Growth Cycle
Before addressing causes, it helps to understand how hair actually grows. Each hair follicle operates on an independent cycle with three phases:
- Anagen (growth phase) — active hair production, lasting 2–7 years. Approximately 85–90% of scalp hairs are in this phase at any time.
- Catagen (transition phase) — follicle shrinks and detaches from blood supply, lasting 2–3 weeks.
- Telogen (resting/shedding phase) — hair is shed and the follicle rests before re-entering anagen, lasting 3–4 months.
Normal daily shedding is 50–100 hairs. When a significant stressor disrupts the anagen phase — nutritional deficiency, hormonal shift, illness, surgery, extreme stress — large numbers of follicles simultaneously enter telogen, producing the diffuse shedding known as telogen effluvium, typically appearing 2–4 months after the triggering event.
Types of Hair Loss: A Clinical Overview
Androgenetic Alopecia (AGA)
The most common form — affecting approximately 50% of men by age 50 and 40% of women by age 70. Driven by the conversion of testosterone to dihydrotestosterone (DHT) via the enzyme 5-alpha reductase. DHT binds to androgen receptors in genetically susceptible follicles, progressively miniaturising them until they can no longer produce visible hair. In men, this produces the classic receding hairline and crown thinning (Hamilton-Norwood pattern). In women, it typically presents as diffuse thinning over the crown with preservation of the frontal hairline (Ludwig pattern).
Telogen Effluvium (TE)
Diffuse shedding triggered by a systemic stressor — nutritional deficiency, illness, surgery, childbirth, extreme psychological stress, rapid weight loss, or hormonal shifts. Usually reversible once the underlying cause is addressed, though recovery takes 6–12 months.
Alopecia Areata (AA)
An autoimmune condition in which T-cells attack hair follicles, producing patchy, well-demarcated hair loss. Can progress to alopecia totalis (complete scalp hair loss) or universalis (complete body hair loss). Strongly associated with other autoimmune conditions (thyroid disease, vitiligo, type 1 diabetes) and psychological stress.
Traction Alopecia
Mechanical damage from chronic tension — tight ponytails, braids, extensions. Reversible if caught early; permanent if follicle scarring occurs.
Scarring Alopecias (Cicatricial)
Inflammatory conditions (lichen planopilaris, frontal fibrosing alopecia, discoid lupus) that permanently destroy follicles. Require specialist management.
The Hormonal Drivers of Hair Loss
DHT and Androgenetic Alopecia
DHT is the primary hormonal driver of pattern hair loss in both sexes. The enzyme 5-alpha reductase (types 1 and 2) converts testosterone to DHT in the scalp, skin, and prostate. Genetically susceptible follicles express higher levels of androgen receptors and are more sensitive to DHT's miniaturising effects.
Pharmaceutical interventions:
- Finasteride (Propecia) — 5-alpha reductase type 2 inhibitor. Reduces scalp DHT by ~70%. Highly effective in men; used off-label in post-menopausal women. Not safe in women of childbearing age.
- Dutasteride — inhibits both type 1 and type 2 5-alpha reductase; more potent than finasteride.
- Minoxidil (Rogaine) — vasodilator that prolongs the anagen phase and increases follicle size. Available topically (2–5%) and orally (low-dose). Works independently of DHT; effective in both AGA and TE.
- Spironolactone — androgen receptor blocker used in women with hormonal hair loss; also reduces adrenal androgen production.
Natural DHT support:
👉 Gaia Saw Palmetto 60vc — Serenoa repens inhibits 5-alpha reductase activity, reducing DHT conversion. The most studied natural DHT blocker with RCT evidence for AGA.
👉 Saw Palmetto Plus — a comprehensive formula combining saw palmetto with additional botanical support.
Oestrogen, Progesterone, and Female Hair Loss
Oestrogen is profoundly hair-protective — it prolongs the anagen phase and counteracts DHT at the follicle level. This explains why hair is often thickest during pregnancy (peak oestrogen) and why postpartum shedding (postpartum telogen effluvium) is so dramatic as oestrogen crashes after delivery.
In perimenopause and menopause, declining oestrogen and progesterone unmask androgenic sensitivity, producing the diffuse thinning characteristic of female pattern hair loss. Oestrogen dominance — paradoxically — can also impair hair growth by disrupting thyroid function and increasing SHBG (sex hormone-binding globulin), which alters the hormonal milieu.
👉 DIM — promotes the conversion of oestrogen to its less proliferative metabolites, supporting hormonal balance relevant to both oestrogen dominance and androgenic hair loss.
Thyroid Dysfunction: The Most Missed Cause
Both hypothyroidism and hyperthyroidism cause diffuse hair loss — yet thyroid function is frequently not tested in hair loss workups, or only TSH is measured (missing subclinical dysfunction). Thyroid hormones are essential for follicle cycling; without adequate T3 and T4, follicles prematurely enter telogen.
Key clinical points:
- Hair loss from hypothyroidism is diffuse, affecting the entire scalp and often the outer third of the eyebrows — a classic sign
- Even subclinical hypothyroidism (elevated TSH with normal T4) can cause significant hair loss
- Hashimoto's thyroiditis — the most common cause of hypothyroidism — is an autoimmune condition that also increases risk of alopecia areata
- Selenium is essential for thyroid hormone conversion (T4 → T3) and thyroid peroxidase function
Cortisol, Stress, and the HPA Axis
Chronic psychological stress is one of the most potent triggers of hair loss, operating through multiple mechanisms:
- Cortisol directly inhibits hair follicle stem cell activity — elevated cortisol suppresses the proliferation of follicle stem cells required for anagen initiation
- Cortisol depletes key hair nutrients — chronic stress increases urinary excretion of zinc, magnesium, and B vitamins
- Stress triggers neurogenic inflammation — substance P released from nerve endings around follicles triggers mast cell degranulation and local inflammation that disrupts the follicle cycle
- HPA dysregulation impairs sex hormone balance — the pregnenolone steal effect reduces progesterone and DHEA, worsening androgenic hair loss
A 2021 study in Nature demonstrated that chronic stress elevates corticosterone, which inhibits the Gas6 signalling pathway required for hair follicle stem cell activation — providing a direct mechanistic link between stress and hair loss.
👉 Ashwagandha — reduces cortisol by up to 30% in RCTs; supports HPA axis resilience and adrenal function.
👉 Designs For Health B Supreme — comprehensive coenzymated B complex; B vitamins are depleted by chronic stress and are essential for follicle cell proliferation.
👉 RN Labs Magnesium Glycinate 180c — depleted by stress; essential for cortisol regulation and follicle health.
Androgens, PCOS, and Female Androgenetic Alopecia
Polycystic ovary syndrome (PCOS) is characterised by elevated androgens (testosterone, DHEA-S, androstenedione), insulin resistance, and often elevated LH. The combination of high androgens and insulin resistance dramatically accelerates DHT-driven follicle miniaturisation in genetically susceptible women. Female AGA in the context of PCOS often presents earlier and more aggressively than in women without androgen excess.
Nutritional Deficiencies: The Root Cause Most Doctors Miss
Iron: The Single Most Important Nutrient for Hair
Iron deficiency is the most common nutritional cause of hair loss worldwide — and the most underdiagnosed. Iron is essential for ribonucleotide reductase, the enzyme that drives DNA synthesis in rapidly dividing follicle cells. Without adequate iron, follicles cannot sustain the anagen phase.
Critical clinical point: Standard haemoglobin testing misses iron deficiency in hair loss. Serum ferritin is the relevant marker — and the threshold for hair loss is far higher than the threshold for anaemia. Studies consistently show hair loss occurs at ferritin levels below 30–50 ng/mL, even with normal haemoglobin. Target ferritin above 70 ng/mL for optimal hair growth.
Women of reproductive age, vegetarians, vegans, and athletes are at highest risk. Heavy menstrual bleeding is a major driver of chronic iron depletion.
👉 Designs For Health Ferro Supreme 30caps — practitioner-grade iron bisglycinate with superior bioavailability and minimal gastrointestinal side effects.
Zinc: The Follicle Mineral
Zinc is a cofactor for over 300 enzymes involved in cell division, protein synthesis, and DNA repair — all critical in the rapidly proliferating follicle matrix. Zinc also inhibits 5-alpha reductase activity (reducing DHT) and regulates androgen receptor sensitivity. Low zinc is consistently found in patients with alopecia areata and telogen effluvium.
👉 Zinc Citrate 25mg — highly bioavailable zinc citrate at a therapeutic dose.
👉 Pure Encapsulations Zinc Citrate — practitioner-grade zinc citrate.
Biotin (Vitamin B7): Overhyped but Not Irrelevant
Biotin deficiency causes brittle hair and nails, but true deficiency is rare in people eating a varied diet. The evidence for biotin supplementation in the absence of deficiency is weak. However, biotin is a cofactor for carboxylase enzymes involved in fatty acid synthesis — relevant to scalp sebum production and follicle membrane integrity.
👉 Biotin Complex Hair & Skin — combines biotin with complementary nutrients for hair and skin support.
👉 Harker Skin, Hair & Nails 60caps — a comprehensive multi-nutrient formula targeting skin, hair, and nail health.
Vitamin D: The Follicle Activator
Vitamin D receptors (VDR) are expressed in hair follicle keratinocytes and play a direct role in follicle cycling — specifically in initiating the anagen phase. Vitamin D deficiency is significantly associated with alopecia areata and telogen effluvium. NZ's latitude makes deficiency extremely common, particularly in winter. Target 25(OH)D above 100 nmol/L for optimal hair and immune function.
👉 Solgar Vitamin D3 1000IU — reliable, well-absorbed vitamin D3.
👉 Doctor's Best Vitamin D3 (1000IU) — high-quality softgel formulation.
Protein and Amino Acids
Hair is approximately 95% keratin — a structural protein. Inadequate dietary protein directly impairs keratin synthesis and forces the body to prioritise protein for vital organs over hair production. Crash dieting, restrictive eating, and very low-calorie diets are classic triggers of telogen effluvium.
L-cysteine is the rate-limiting amino acid for keratin synthesis. L-lysine is essential for iron absorption and collagen cross-linking in the follicle. A high-protein diet (1.2–1.6g/kg body weight) with diverse amino acid sources is foundational.
B Vitamins: Folate, B12, and the Methylation Connection
Folate and B12 are essential for DNA synthesis and cell division in the follicle matrix — one of the most rapidly dividing cell populations in the body. MTHFR variants impair methylfolate production, reducing the availability of active folate for follicle cell replication. Elevated homocysteine (a marker of B12/folate insufficiency) is associated with premature hair greying and follicle damage.
👉 Designs For Health B Supreme — comprehensive coenzymated B complex including methylfolate and methylcobalamin.
Alcohol and Hair Loss
Alcohol is a significant but underappreciated driver of hair loss, operating through multiple mechanisms:
- Nutritional depletion — alcohol impairs absorption of zinc, iron, folate, B12, and vitamin C; all critical for follicle function
- Liver dysfunction — the liver metabolises sex hormones; impaired hepatic function leads to oestrogen accumulation and altered androgen metabolism, worsening hormonal hair loss
- Elevated oestrogen — alcohol increases aromatase activity, converting more testosterone to oestrogen; in men this can paradoxically worsen androgenetic alopecia through complex hormonal feedback
- Cortisol elevation — alcohol activates the HPA axis, raising cortisol and triggering the stress-related hair loss cascade
- Dehydration and scalp circulation — chronic alcohol use impairs peripheral circulation, reducing nutrient delivery to follicles
- Disrupted sleep — alcohol fragments sleep architecture, reducing growth hormone secretion (which peaks during deep sleep and supports follicle anagen)
Even moderate alcohol consumption (2–3 standard drinks daily) can meaningfully impair hair health through these combined mechanisms.
Weather, Seasonality, and Hair Loss
Hair loss has a genuine seasonal pattern — studies using trichograms consistently show a peak in telogen hairs in late summer/autumn (February–April in the Southern Hemisphere), with a corresponding shedding peak 2–3 months later in autumn/winter. The mechanism is thought to involve photoperiod changes (day length) affecting melatonin and prolactin signalling in follicles.
Cold weather reduces scalp circulation, potentially slowing nutrient delivery to follicles. Low humidity increases hair shaft brittleness and breakage (though this is not true hair loss — the follicle is intact). UV exposure damages the hair shaft protein structure and can trigger scalp inflammation.
In New Zealand's climate, the combination of winter vitamin D deficiency, reduced outdoor activity, and seasonal HPA axis changes creates a genuine convergence of hair loss risk factors in the June–August period.
Scalp Health: The Foundation of Hair Growth
A healthy scalp is the prerequisite for healthy hair. Key scalp conditions that impair hair growth include:
- Seborrhoeic dermatitis — driven by Malassezia yeast overgrowth; causes inflammation, flaking, and follicle disruption. Zinc pyrithione, selenium sulphide, and ketoconazole shampoos are first-line treatments.
- Scalp psoriasis — autoimmune-driven inflammation; requires specialist management.
- Folliculitis — bacterial or fungal infection of follicles; requires targeted antimicrobial treatment.
- Scalp microbiome dysbiosis — emerging evidence suggests the scalp microbiome plays a role in follicle health analogous to the gut microbiome's role in systemic health.
A Comprehensive Hair Loss Investigation: What to Test
A thorough hair loss workup should include:
- Full blood count — haemoglobin, MCV
- Serum ferritin — target >70 ng/mL for hair growth
- Thyroid panel — TSH, free T4, free T3, thyroid antibodies (TPO, TgAb)
- Sex hormones — testosterone (total and free), DHEA-S, LH, FSH, oestradiol, progesterone (day 21 if cycling)
- SHBG — sex hormone-binding globulin
- Zinc and copper — serum levels
- Vitamin D — 25(OH)D
- B12 and folate — serum and/or active B12
- Homocysteine — marker of methylation status
- Fasting glucose and insulin — to assess insulin resistance (relevant in PCOS and AGA)
- CRP — inflammatory marker
- DUTCH test — comprehensive urinary hormone metabolite testing for oestrogen metabolism, cortisol, and adrenal function
A Practical Hair Loss Support Protocol
Based on the evidence above, a comprehensive nutritional and lifestyle protocol for hair loss might include:
- Iron — test ferritin first; supplement if below 70 ng/mL. 👉 Designs For Health Ferro Supreme
- Zinc — 15–30mg daily. 👉 Zinc Citrate 25mg or Pure Encapsulations Zinc Citrate
- Vitamin D3 — test and supplement to 100–150 nmol/L. 👉 Solgar Vitamin D3 1000IU or Doctor's Best Vitamin D3
- B vitamins (methylated) — folate, B12, B6 for methylation and follicle cell division. 👉 Designs For Health B Supreme
- DHT support — 👉 Gaia Saw Palmetto 60vc or Saw Palmetto Plus
- Hormonal balance (women) — 👉 DIM for oestrogen metabolism support
- Stress/cortisol — 👉 Ashwagandha
- Magnesium — 👉 RN Labs Magnesium Glycinate 180c
- Comprehensive hair formula — 👉 Harker Skin, Hair & Nails or Biotin Complex Hair & Skin
- Scalp tonic — 👉 Weleda Revitalising Hair Tonic
- High-protein diet — 1.2–1.6g/kg body weight daily, diverse amino acid sources
- Reduce alcohol — even moderate reduction meaningfully improves the hormonal and nutritional environment for hair growth
- Optimise sleep — growth hormone secretion during deep sleep is critical for anagen maintenance
- Manage stress — HPA axis dysregulation is a direct follicle suppressor
The Bottom Line
Hair loss is rarely a single-cause problem. In most cases it is the visible expression of a convergence of factors — nutritional depletion, hormonal imbalance, thyroid dysfunction, chronic stress, poor sleep, alcohol, and genetic susceptibility — operating simultaneously on a follicle system that is exquisitely sensitive to systemic health.
The good news: most of these drivers are modifiable. A systematic investigation followed by targeted nutritional, hormonal, and lifestyle intervention can meaningfully slow, halt, or reverse hair loss in the majority of cases — particularly when addressed early.
Our dispensary stocks practitioner-grade formulations selected for bioavailability and clinical relevance. Browse our Wellness Dispensary or contact our team for personalised guidance.
Disclaimer: This article is for informational purposes only and does not constitute medical advice. Hair loss diagnosis and treatment should be managed by a qualified healthcare professional.