Hormones and Hair Loss: DHT, Thyroid, Estrogen, and What Actually Helps

Hair loss is one of those symptoms that hits differently. It's not life-threatening, it's not painful, but it affects how you see yourself every time you look in the mirror. And for a symptom this visible and this distressing, it's remarkably poorly evaluated by most clinicians — who either dismiss it as cosmetic, attribute it to stress or genetics without investigation, or jump to topical treatments without understanding what's causing it.

If you're losing hair, hormones are often a primary driver. Understanding which hormones are involved — and which ones aren't — determines whether treatment actually works or just manages the surface while the cause continues.

The Hormonal Causes of Hair Loss

DHT: The Primary Culprit in Pattern Hair Loss

Dihydrotestosterone (DHT) is the hormone most directly responsible for androgenetic alopecia — the most common form of hair loss in both men and women.

How it works:

Testosterone is converted to DHT by the enzyme 5-alpha reductase. DHT is 2-3 times more potent than testosterone at androgen receptors. In hair follicles that are genetically sensitive to DHT (primarily on the top and front of the scalp), DHT causes:

1. Miniaturization — Hair follicles progressively shrink, producing thinner, shorter, lighter hairs with each growth cycle
2. Shortened growth phase (anagen) — Hairs spend less time growing and more time in the resting/shedding phase
3. Eventually, the follicle produces only vellus hairs — The fine, barely visible hairs that eventually stop growing entirely

The genetic component: Not everyone with the same DHT levels experiences hair loss. The critical variable is the sensitivity of individual hair follicles to DHT, which is genetically determined. This is why two men with identical testosterone levels can have completely different hairlines.

In men: Pattern hair loss (receding hairline, crown thinning) affects approximately 50% of men by age 50 and up to 80% by age 80. It can begin as early as the late teens.

In women: Female pattern hair loss presents differently — typically as diffuse thinning across the top of the scalp rather than hairline recession. It affects about 40% of women by age 50, though it's often less visibly dramatic than male pattern hair loss.

Thyroid Dysfunction: The Overlooked Connection

Both hypothyroidism and hyperthyroidism can cause hair loss, but they present differently:

Hypothyroidism:

• Diffuse thinning across the entire scalp (not patterned)
• Hair becomes dry, brittle, and coarse
• Thinning of the outer third of the eyebrows (a classic sign)
• Slow hair growth
• Increased shedding

Hyperthyroidism:

• Fine, thin hair texture
• Increased shedding
• Hair may become softer and more fragile

Hashimoto's thyroiditis deserves special mention because the autoimmune process can cause hair loss even when thyroid levels are technically normal. The inflammatory component and antibody activity can affect hair follicles independently of thyroid hormone status. Additionally, Hashimoto's is associated with alopecia areata (autoimmune hair loss).

Why thyroid is often missed: If your doctor only checks TSH and it's within the reference range, early thyroid dysfunction causing hair loss can be overlooked. A complete thyroid panel — including free T3, free T4, reverse T3, and thyroid antibodies — provides a more complete picture.

Estrogen and Progesterone

Estrogen's role in hair:

• Estrogen prolongs the growth phase (anagen) of the hair cycle
• High estrogen states (like pregnancy) often produce thicker, more robust hair
• Declining estrogen (perimenopause, menopause) reduces this protective effect, allowing DHT-driven thinning to accelerate
• Post-partum hair loss (telogen effluvium) occurs when estrogen drops rapidly after delivery

Progesterone's role:

• Progesterone inhibits 5-alpha reductase, reducing DHT production
• Low progesterone (common in perimenopause, anovulatory cycles, and chronic stress) removes this protective effect
• Synthetic progestins in some hormonal contraceptives have androgenic activity and can actually promote hair loss

The perimenopause pattern: Many women notice hair thinning beginning in their 40s. This coincides with declining progesterone (less 5-alpha reductase inhibition = more DHT at the follicle), declining estrogen (shorter anagen phase), and unchanged or relatively increased androgen influence.

Insulin Resistance and PCOS

Insulin resistance drives hair loss through multiple mechanisms:

• Increases ovarian androgen production — Leading to elevated testosterone and DHEA
• Decreases SHBG — More free testosterone available for conversion to DHT
• Promotes inflammation — Which can damage hair follicles
• Common in PCOS — Where androgen excess is a defining feature

Women with PCOS may experience both scalp hair thinning and increased facial/body hair (hirsutism) — seemingly contradictory but both driven by androgen excess acting on different hair follicle types.

Cortisol and Stress Hormones

Chronic stress causes hair loss through several pathways:

• Telogen effluvium — Stress shifts hair follicles from the growth phase to the resting phase prematurely. 2-3 months after a significant stressor, you experience diffuse shedding. This is usually temporary and reversible.
• Cortisol effects — Chronic cortisol elevation can impair hair growth directly and disrupts other hormones (thyroid, sex hormones) that affect hair.
• Inflammation — Chronic stress increases systemic inflammation, which can damage hair follicles.

Iron and Ferritin

Iron deficiency is technically a nutritional cause rather than hormonal, but it's so commonly associated with hair loss — and so frequently overlooked — that it belongs in this discussion.

Ferritin (stored iron) below 40-70 ng/mL is associated with increased hair shedding, even when hemoglobin is normal and you're not technically anemic. Many labs list the reference range as starting at 12-15 ng/mL, which means a ferritin of 20 is called "normal" despite being suboptimal for hair growth.

At CORAL, Dr. Kim checks ferritin as part of any hair loss evaluation because optimizing it is one of the simplest, most effective interventions available.

The Diagnostic Workup

A proper hair loss evaluation should include:

History:

• Pattern and timeline of hair loss
• Family history (both sides)
• Menstrual history and hormonal status
• Medications (many drugs cause hair loss)
• Diet and nutritional habits
• Stress and sleep patterns
• Other symptoms suggesting hormonal dysfunction

Labs:

• Complete thyroid panel — TSH, free T4, free T3, TPO antibodies, thyroglobulin antibodies
• Total and free testosterone — Elevated in PCOS and other androgen excess states
• DHEA-S — Adrenal androgen
• Ferritin — Optimal range for hair: 70-100 ng/mL
• CBC — Anemia screening
• Vitamin D — Deficiency is associated with hair loss and autoimmune conditions
• Fasting insulin and glucose — Insulin resistance screening
• Estradiol and progesterone — Particularly in perimenopausal women
• SHBG — Low SHBG means more free androgens
• Zinc — Deficiency can cause hair loss
• CRP or ESR — Inflammatory markers, particularly if autoimmune hair loss is suspected
• ANA — If autoimmune conditions are being considered

Treatment Based on Cause

DHT-Mediated Hair Loss

Finasteride (men):

• Blocks 5-alpha reductase type II, reducing DHT by approximately 70%
• FDA-approved for male pattern hair loss
• Most effective when started early, before significant follicle miniaturization
• Side effects include sexual dysfunction in 1-2% of users (controversial — some reports suggest higher rates)
• 1 mg daily is the standard dose

Dutasteride (men):

• Blocks both 5-alpha reductase type I and II, reducing DHT by approximately 90%
• More potent than finasteride but not FDA-approved for hair loss (FDA-approved for prostate enlargement)
• Used off-label when finasteride isn't sufficient

Spironolactone (women):

• Anti-androgen that blocks DHT at the receptor and reduces androgen production
• Commonly prescribed for female pattern hair loss, typically 100-200 mg daily
• Also helps with hormonal acne and hirsutism
• Contraindicated in pregnancy (teratogenic)
• Requires potassium monitoring

Minoxidil (men and women):

• Topical (2% or 5%) or oral (low-dose: 0.625-2.5 mg)
• Mechanism: vasodilator that prolongs the anagen phase
• Not hormonal but commonly used alongside hormonal treatments
• Must be continued to maintain results

Low-dose oral minoxidil:

• Increasingly used as an alternative to topical
• Better compliance (once daily pill vs. twice daily topical application)
• More consistent absorption
• Side effects can include increased body hair and mild fluid retention

Thyroid-Related Hair Loss

Treatment: Optimize thyroid function with appropriate medication (levothyroxine, combination T4/T3, or NDT). Hair regrowth typically begins within 2-3 months of reaching optimal thyroid levels but may take 6-12 months for full recovery.

Key: TSH should be optimized to the lower end of the reference range (0.5-2.0), and free T3 should be in the upper half of normal. "Normal" thyroid function with suboptimal levels may not be sufficient for hair recovery.

Estrogen/Progesterone-Related Hair Loss

HRT during perimenopause/menopause can slow or reverse hormonally driven hair thinning by:

• Replacing declining estrogen (prolongs anagen phase)
• Providing progesterone (inhibits 5-alpha reductase)
• Reducing the relative androgen dominance that occurs with estrogen decline

Insulin Resistance/PCOS

Address insulin resistance:

• Metformin or inositol to improve insulin sensitivity
• Dietary changes (reduce refined carbohydrates, increase protein and fiber)
• Exercise (resistance training improves insulin sensitivity)
• Weight loss if applicable

Reduce androgens:

• Spironolactone
• Oral contraceptives with anti-androgenic progestins (when appropriate)

Telogen Effluvium (Stress-Related)

Treatment: Address the underlying stressor. Optimize nutrition (especially iron, vitamin D, zinc, biotin). Be patient — hair growth cycles are slow, and recovery from telogen effluvium typically takes 6-12 months.

Nutritional Optimization

Regardless of the primary cause, nutritional support is essential:

• Ferritin — Supplement iron if below 70 ng/mL
• Vitamin D — Optimize to 50-80 ng/mL
• Zinc — 15-30 mg daily if deficient
• Biotin — 5,000-10,000 mcg daily (note: biotin can interfere with thyroid and cardiac lab tests — stop 48 hours before blood draws)
• Protein — Hair is made of keratin (a protein). Inadequate protein intake impairs hair growth
• Omega-3 fatty acids — Anti-inflammatory, support scalp health

The Timeline of Treatment

Hair growth is slow. This is the hardest part for most people:

• Most treatments take 3-6 months before visible improvement begins
• Full results typically require 12-18 months of consistent treatment
• Shedding at the start of treatment is common and expected (old hairs being pushed out by new growth)
• Consistency matters — intermittent treatment produces intermittent results
• Early intervention matters — it's easier to maintain existing hair than to regrow lost follicles

Getting Evaluated

If you're losing hair and don't know why — or if you've been told "it's genetic" without any testing — a proper hormonal evaluation can identify treatable causes and guide targeted treatment rather than generic interventions.

Start at [coral.clinic/start](https://coral.clinic/start). Dr. Kim will order the right labs, identify the hormonal drivers, and build a treatment plan that addresses the cause — not just the cosmetic outcome.

Your hair is telling you something about your hormones. It's worth finding out what.