SHBG (Sex Hormone-Binding Globulin)

What It Is

SHBG (Sex Hormone-Binding Globulin) is a protein produced by the liver that acts as a molecular taxi service for sex hormones in the bloodstream. It binds to testosterone and estrogen, rendering them temporarily inactive—like packages in storage rather than packages in use.

Here's why SHBG matters more than most women realize:

When you get hormone testing, most labs measure total testosterone or total estrogen—the sum of all hormone in your blood, both bound (inactive) and free (active). But only free (unbound) hormones are biologically active—able to bind to receptors and create effects in your body.

Think of it this way:

• Total hormone = all the money in your bank account (checking + savings)
• Bound hormone = money in savings (technically yours, but not available to spend)
• Free hormone = money in checking (available for immediate use)

SHBG determines how much of your hormone stays "in savings" (bound, inactive) versus how much is "in checking" (free, active, creating effects).

What SHBG binds:

• Testosterone: About 60-70% of testosterone is tightly bound to SHBG (inactive)
• Estrogen: About 30-40% of estrogen is bound to SHBG (inactive)
• The rest: Bound loosely to albumin (a different protein, easier to access) or circulating free (fully active)

Why this matters clinically:

You can have "normal" total testosterone or estrogen on a lab test but still experience severe symptoms of hormone deficiency (or excess) because SHBG is too high or too low, altering how much hormone is actually available for your body to use.

Example 1: High SHBG

• Total testosterone: 40 ng/dL ("normal" range)
• SHBG: Very high
• Result: Most testosterone is bound to SHBG → very low free testosterone
• Symptoms: Low libido, fatigue, brain fog, muscle loss, depression
• Doctor says: "Your testosterone is normal"
• You feel: "But I feel terrible. Why doesn't anyone believe me?"

Example 2: Low SHBG

• Total testosterone: 40 ng/dL ("normal" range)
• SHBG: Very low
• Result: Most testosterone is free (unbound) → high free testosterone
• Symptoms: Acne, oily skin, facial hair, hair loss, irritability
• Doctor says: "Your testosterone is normal"
• You feel: "But I have acne and hair growth like I never had before. What's happening?"

This is why SHBG is the missing piece in understanding hormone-related symptoms during perimenopause and menopause. It's not just about how much hormone you have—it's about how much is available to use.

Why It Matters During Perimenopause/Menopause

SHBG levels fluctuate during perimenopause and menopause, often in ways that worsen symptoms or create confusing symptom patterns.

What influences SHBG:

SHBG increases with:

• High estrogen → estrogen stimulates liver production of SHBG
• Hyperthyroidism (overactive thyroid) → increases SHBG production
• Aging → SHBG tends to rise with age
• Low insulin → insulin suppresses SHBG, so low insulin → higher SHBG
• Chronic stress → can increase SHBG in some women
• Certain medications: Estrogen therapy (especially oral), thyroid hormone (if dose is too high), some antiepileptic drugs

SHBG decreases with:

• Insulin resistance → high insulin suppresses SHBG production (this is the most common driver in perimenopause)
• Low estrogen → as estrogen declines, SHBG often declines
• Hypothyroidism (underactive thyroid) → reduces SHBG production
• PCOS (polycystic ovary syndrome) → insulin resistance + androgen excess → low SHBG
• Obesity (especially visceral fat) → increases insulin resistance → lowers SHBG
• High testosterone → some evidence that androgens suppress SHBG
• Certain medications: Androgens, corticosteroids, growth hormone

How perimenopause/menopause affects SHBG:

Early perimenopause (Electric Cougar):

• Estrogen surges can temporarily increase SHBG → more testosterone and estrogen get bound → lower free hormones
• Result: Even during estrogen surges, some women feel symptoms of hormone deficiency (low libido, fatigue) because so much hormone is bound
• Alternatively: If insulin resistance is developing (common in perimenopause), SHBG may be declining → more free testosterone → acne, facial hair, oily skin

Mid-perimenopause (Wild Tide):

• SHBG fluctuates with erratic estrogen levels → symptoms are unpredictable
• Insulin resistance is worsening for many women → SHBG declines → free testosterone rises → androgen-related symptoms increase (acne, hair growth, hair loss)

Late perimenopause/menopause (Henapause/Pause):

• Estrogen declines → SHBG often declines (less estrogen to stimulate SHBG production)
• Insulin resistance is common → further lowers SHBG
• Result: Lower SHBG → more free testosterone available
• Paradox: Even though total testosterone is declining, some women experience androgen-related symptoms (acne, hair growth, hair loss) because free testosterone is relatively high compared to estrogen
• This is relative androgen dominance (not true high testosterone, just high testosterone relative to low estrogen + low SHBG)

Post-menopause (Phoenix/Golden):

• SHBG levels stabilize at a "new normal" (often lower than reproductive years, unless estrogen therapy is used)
• Women on oral estrogen therapy often have high SHBG → can worsen symptoms of low testosterone (low libido, fatigue) even if testosterone levels are "normal"
• Women with insulin resistance have low SHBG → may continue to have androgen-related symptoms

Why SHBG complicates hormone replacement therapy (HRT):

Oral estrogen (taken by mouth) increases SHBG significantly because it passes through the liver on "first pass" before entering general circulation. The liver responds by producing more SHBG.

Result:

• Oral estrogen → high SHBG → more testosterone (and estrogen) get bound → lower free testosterone
• Many women on oral estrogen therapy report persistent low libido despite "normal" testosterone levels—this is why

Transdermal estrogen (patch, gel, cream) bypasses the liver initially → does not increase SHBG as much → allows more free testosterone to remain available

Clinical pearl: Women on oral estrogen who have low libido, fatigue, or low mood despite "normal" testosterone may benefit from:

1. Switching to transdermal estrogen (to reduce SHBG increase)
2. Adding testosterone therapy (to overcome the SHBG binding effect)
3. Testing free testosterone (not just total testosterone)

How It Works

Mechanism of action:

SHBG is a carrier protein produced primarily by the liver. It circulates in the bloodstream and binds sex hormones:

Binding affinity (how tightly SHBG holds different hormones):

• Strongest: DHT (dihydrotestosterone, a potent form of testosterone) → almost all DHT is bound
• Strong: Testosterone → about 60-70% bound to SHBG
• Moderate: Estradiol (estrogen) → about 30-40% bound to SHBG

The result:

• Hormones bound to SHBG are biologically inactive → cannot bind to hormone receptors or exert effects
• Hormones must dissociate (unbind) from SHBG before they can enter cells and activate receptors
• This creates a "reservoir" of hormone that can be released as needed

The equilibrium:

There's a dynamic balance between bound and free hormone. As free hormone is used up (metabolized or excreted), more hormone is released from SHBG.

Think of it as a buffer:

• SHBG prevents dramatic swings in free hormone levels
• Provides a steady, controlled release of hormone
• Protects against both deficiency and excess

When SHBG is too high:

• Too much hormone is "locked away" → not enough free hormone available
• Symptoms of hormone deficiency (low libido, fatigue, low mood, brain fog)

When SHBG is too low:

• Too much hormone is free and active → can create symptoms of excess
• Symptoms of androgen excess (acne, oily skin, facial hair, hair loss) or estrogen excess (heavy periods, breast tenderness)

SHBG's relationship with other hormones and factors:

SHBG + Estrogen:

• Estrogen increases SHBG production → more SHBG is produced when estrogen is high
• This creates a negative feedback loop: High estrogen → high SHBG → less free estrogen → symptoms improve (preventing estrogen overload)
• When estrogen declines (menopause), SHBG also declines

SHBG + Testosterone:

• SHBG binds testosterone tightly → determines how much testosterone is free and active
• Low SHBG → high free testosterone → androgen-related symptoms (acne, hair growth, oily skin, hair loss, irritability)
• High SHBG → low free testosterone → symptoms of testosterone deficiency (low libido, fatigue, low motivation, muscle loss)

SHBG + Insulin:

• Insulin suppresses SHBG production (this is one of the most important clinical relationships)
• Insulin resistance (high insulin) → low SHBG → high free testosterone
• This is the mechanism behind PCOS and menopause-related androgen excess
• Improving insulin sensitivity (via diet, exercise, weight loss, medications like metformin) → SHBG rises → free testosterone declines → androgen symptoms improve

SHBG + Thyroid Hormones:

• Hyperthyroidism (high thyroid hormone) → increases SHBG
• Hypothyroidism (low thyroid hormone) → decreases SHBG
• Thyroid dysfunction is common in perimenopause → can affect SHBG and complicate hormone symptoms

SHBG + Cortisol (Stress Hormone):

• Chronic stress can increase SHBG in some women → worsens symptoms of hormone deficiency
• High cortisol also drives insulin resistance → which lowers SHBG → complex, bidirectional relationship

SHBG + Body Composition:

• Visceral fat (abdominal fat) → increases insulin resistance → lowers SHBG
• Muscle mass → improves insulin sensitivity → SHBG may rise
• Weight loss (especially loss of visceral fat) → improves insulin sensitivity → SHBG rises → free testosterone declines → androgen symptoms improve

What It Looks Like

When Optimal (Healthy SHBG Levels)

Lab values:

• Normal SHBG range for women: 20-100 nmol/L (varies by lab)
• Optimal range (functional medicine): 40-80 nmol/L
• Note: "Optimal" depends on individual factors (age, hormone levels, symptoms)

What it feels like:

• Hormone levels match how you feel → "normal" labs correlate with normal symptoms
• Balanced libido, energy, mood
• Stable skin, hair, and body composition
• No unexplained symptoms despite "normal" hormone levels

When High (Elevated SHBG)

Lab values:

• SHBG >100 nmol/L (though even high-normal SHBG can cause symptoms in some women)

Causes:

• High estrogen (especially oral estrogen therapy)
• Hyperthyroidism
• Low insulin (very lean body composition, eating disorders, chronic illness)
• Aging
• Liver disease (in some cases)
• Certain medications

Physical symptoms (from low free testosterone and/or estrogen):

• Low or absent libido → reduced sexual desire, difficulty with arousal
• Fatigue → persistent low energy, exhaustion
• Muscle loss → difficulty building or maintaining muscle despite exercise
• Bone density loss → increased osteoporosis risk
• Vaginal dryness, painful sex (if free estrogen is also low)
• Joint pain → testosterone supports connective tissue health

Cognitive symptoms:

• Brain fog → difficulty concentrating, slow thinking
• Memory problems → forgetfulness
• Low motivation → reduced drive, ambition, initiative

Emotional symptoms:

• Low mood, depression → feeling flat, hopeless, low vitality
• Reduced confidence → self-doubt, difficulty advocating for self
• Low assertiveness → passivity, people-pleasing
• Anhedonia → inability to feel pleasure or joy

The clinical frustration:

• Labs show "normal" total testosterone and estrogen
• Doctor says "everything looks fine"
• You feel terrible but have no explanation
• Solution: Test SHBG and calculate free testosterone/free estrogen

When Low (Decreased SHBG)

Lab values:

• SHBG <20 nmol/L (though even low-normal SHBG can cause symptoms)

Causes:

• Insulin resistance (most common cause in perimenopause/menopause)
• Obesity (especially visceral fat)
• Hypothyroidism
• PCOS
• High androgen levels
• Certain medications (androgens, corticosteroids)

Physical symptoms (from high free testosterone and/or estrogen):

Androgen-related (from high free testosterone):

• Acne → especially jawline, chest, back (adult-onset or worsening acne)
• Oily skin → increased sebum production
• Facial hair growth (hirsutism) → upper lip, chin, sideburns
• Male-pattern hair loss → thinning at temples, crown (androgenic alopecia)
• Body hair growth → chest, abdomen, back, inner thighs

Estrogen-related (from high free estrogen, if estrogen levels are also elevated):

• Heavy periods → if still cycling
• Breast tenderness
• Bloating, water retention
• Mood swings, irritability

Metabolic symptoms:

• Insulin resistance (both cause and consequence of low SHBG)
• Weight gain (especially abdominal fat)
• Difficulty losing weight
• Signs of metabolic syndrome (high triglycerides, low HDL cholesterol, high blood pressure)

The clinical pattern:

• Labs show "normal" total testosterone
• But you have acne, facial hair, hair loss, oily skin
• Doctor is confused ("your testosterone isn't high")
• Explanation: Total testosterone is normal, but SHBG is low → free testosterone is high
• Solution: Test SHBG and calculate free testosterone

Phase Impact

Baseline (Regular Cycle, Pre-Perimenopause): SHBG fluctuates slightly with the menstrual cycle (rises when estrogen rises around ovulation) but is generally stable month to month. Insulin sensitivity is typically healthy, supporting normal SHBG levels.

Electric Cougar (Early Perimenopause): Estrogen surges can temporarily increase SHBG → more testosterone and estrogen get bound → some women experience symptoms of hormone deficiency despite high total hormone levels. Alternatively, if insulin resistance is developing (common with stress, weight gain, aging), SHBG may decline → free testosterone rises → acne, facial hair, oily skin emerge.

Wild Tide (Mid-Perimenopause): SHBG fluctuates unpredictably with erratic estrogen levels. Insulin resistance is worsening for many women → SHBG declines → free testosterone rises → androgen symptoms intensify (acne, hair growth, hair thinning). This is often the phase when women first notice "I'm breaking out like a teenager" or "I have facial hair for the first time."

Henapause (Late Perimenopause, 7-11 Months Without Period): Estrogen declines → SHBG often declines. Insulin resistance is common → further lowers SHBG. Result: Free testosterone is relatively high (even as total testosterone declines) → androgen symptoms persist (acne, hair growth, hair loss). This is "relative androgen dominance"—not high testosterone, but high free testosterone relative to low estrogen.

The Pause (Menopause, 12+ Months Without Period): SHBG stabilizes at lower levels than reproductive years (due to low estrogen and common insulin resistance). Women with insulin resistance continue to have low SHBG → androgen symptoms may persist. Women on oral estrogen therapy may have high SHBG → low free testosterone → low libido, fatigue, low motivation despite "normal" labs.

Phoenix Phase (Early Post-Menopause, 2-10 Years After Last Period): SHBG remains influenced by estrogen therapy (if used) and insulin sensitivity. Women who improve insulin sensitivity (via strength training, low-carb eating, weight loss) often see SHBG rise → free testosterone declines → androgen symptoms improve. Women on transdermal estrogen maintain more balanced SHBG than those on oral estrogen.

Golden Sovereignty (Established Post-Menopause, 7+ Years After Last Period): SHBG levels are stable, determined primarily by estrogen therapy use (if any), thyroid function, and metabolic health. Women who maintain muscle mass, manage insulin resistance, and optimize thyroid function have healthier SHBG levels and better hormone balance.

Testing & Optimization

When to Test

You should test SHBG if:

• Hormone levels are "normal" but you have significant symptoms (low libido, fatigue, acne, hair growth, hair loss)
• You're on hormone replacement therapy (HRT) but symptoms haven't improved
• You have signs of insulin resistance (abdominal weight gain, energy crashes, cravings)
• You have signs of thyroid dysfunction (fatigue, weight changes, hair loss, temperature sensitivity)
• You're considering or currently taking testosterone therapy (to monitor free testosterone)

What tests to request:

SHBG (blood test):

• Measures SHBG level in nmol/L
• Fasting is ideal but not always required
• Normal range: 20-100 nmol/L (varies by lab)

Total testosterone:

• Measures all testosterone (bound + free)
• Normal range for women: 15-70 ng/dL (varies by lab and age)

Free testosterone:

• Calculated free testosterone (from total testosterone + SHBG) → most common, least expensive
• Direct free testosterone assay → less common, not always accurate
• Equilibrium dialysis → gold standard but expensive, not widely available

Total estradiol:

• Measures all estradiol (bound + free)

Free estradiol:

• Less commonly tested, but can be calculated from total estradiol + SHBG

Other tests to consider:

• Fasting insulin and glucose → assess insulin resistance (the most common cause of low SHBG)
• TSH, free T3, free T4 → assess thyroid function (affects SHBG)
• Lipid panel → assess for metabolic syndrome (linked to insulin resistance and low SHBG)

Best timing for testing:

• Morning (8-10 AM) → testosterone levels peak in morning
• Fasting (if testing insulin and glucose)
• Any day of cycle (if still cycling, though SHBG is most stable in follicular phase—days 3-5)

How to interpret results:

High SHBG + "normal" total testosterone:

• Likely: Low free testosterone
• Symptoms: Low libido, fatigue, muscle loss, brain fog, depression
• Action: Consider testosterone therapy, switch from oral to transdermal estrogen (if on HRT), address thyroid if hyperthyroid

Low SHBG + "normal" total testosterone:

• Likely: High free testosterone
• Symptoms: Acne, oily skin, facial hair, hair loss, irritability
• Action: Address insulin resistance (diet, exercise, weight loss, metformin), improve metabolic health, check for PCOS or thyroid dysfunction

High SHBG + low total testosterone:

• Likely: Very low free testosterone
• Symptoms: Severe symptoms of testosterone deficiency
• Action: Testosterone therapy is likely needed

Low SHBG + high total testosterone:

• Likely: Very high free testosterone
• Symptoms: Severe androgen symptoms
• Action: Address insulin resistance, rule out PCOS or adrenal disorder

Optimization Strategies

1. Address Insulin Resistance (if SHBG is low)

Insulin resistance is the most common cause of low SHBG in perimenopause and menopause.

Strategies to improve insulin sensitivity and raise SHBG:

Nutrition:

• Low-carb or low-glycemic eating → reduces insulin spikes → improves insulin sensitivity → SHBG rises
• Adequate protein (0.7-1.0 g per pound body weight) → supports muscle mass, satiety, stable blood sugar
• Healthy fats (omega-3s, olive oil, avocado) → supports hormone production, reduces inflammation
• Fiber (vegetables, legumes, flaxseeds) → slows glucose absorption, supports gut health
• Intermittent fasting (if appropriate) → gives insulin a chance to drop → improves insulin sensitivity

Exercise:

• Strength training (2-4x per week) → builds muscle → improves insulin sensitivity → raises SHBG
• Cardiovascular exercise (150+ minutes per week) → improves insulin sensitivity, reduces visceral fat
• Post-meal walks (10-15 minutes) → reduces blood sugar spikes → lowers insulin

Weight loss (if needed):

• Loss of visceral fat (abdominal fat) → improves insulin sensitivity → SHBG rises → free testosterone declines → androgen symptoms improve
• Even 5-10% weight loss can significantly improve SHBG and metabolic health

Medications:

• Metformin → improves insulin sensitivity → raises SHBG → reduces free testosterone → androgen symptoms improve
• Highly effective for women with insulin resistance and low SHBG

Supplements:

• Berberine (500 mg 2-3x/day) → improves insulin sensitivity
• Inositol (2-4 g/day) → improves insulin sensitivity, especially in PCOS
• Magnesium (300-400 mg/day) → supports insulin function
• Omega-3s (1-2 g/day) → reduces inflammation, supports metabolic health

2. Optimize Thyroid Function (if SHBG is high or low)

If SHBG is high:

• Check for hyperthyroidism (overactive thyroid) → TSH will be low, free T3/T4 high
• If hyperthyroid, treat with medications (antithyroid drugs, radioactive iodine, or surgery)

If SHBG is low:

• Check for hypothyroidism (underactive thyroid) → TSH will be high, free T3/T4 low
• If hypothyroid, treat with thyroid hormone replacement (levothyroxine or combination T3/T4)
• Optimizing thyroid function can raise SHBG and improve hormone balance

3. Adjust Hormone Replacement Therapy (if SHBG is high on HRT)

If you're on oral estrogen and have high SHBG + low free testosterone:

• Switch from oral to transdermal estrogen (patch, gel, cream)
• Transdermal estrogen bypasses the liver → doesn't increase SHBG as much → allows more free testosterone
• Many women report improved libido, energy, and mood with this switch

If symptoms persist:

• Consider adding testosterone therapy (cream, gel, or pellet)
• Testosterone therapy can overcome the SHBG binding effect and restore free testosterone to healthy levels

4. Lifestyle Strategies for Healthy SHBG

Manage stress:

• Chronic stress can affect SHBG (via cortisol and insulin resistance)
• Practices: meditation, breathwork, therapy, boundaries, adequate rest

Sleep:

• Poor sleep worsens insulin resistance → lowers SHBG
• Prioritize 7-9 hours of quality sleep

Avoid excess alcohol:

• Alcohol affects liver function (SHBG is produced by the liver)
• Alcohol also worsens insulin resistance
• Moderation is key

5. Monitor and Reassess

If you've made lifestyle or medication changes:

• Retest SHBG and free testosterone after 3-6 months
• Assess symptom improvement (libido, energy, skin, hair, mood)
• Adjust interventions as needed

When to Review with Clinician

You should discuss SHBG testing if:

• Hormone levels are "normal" but symptoms are severe (low libido, fatigue, acne, hair growth, hair loss)
• You're on HRT but symptoms haven't improved (especially low libido despite "normal" testosterone)
• You have signs of insulin resistance (abdominal weight gain, energy crashes, cravings, difficulty losing weight)
• You have signs of thyroid dysfunction (fatigue, weight changes, temperature sensitivity, hair loss)
• You're on oral estrogen therapy and have low libido or fatigue
• You have adult-onset or worsening acne, facial hair, or hair loss
• You're considering testosterone therapy and want to understand your baseline free testosterone

What to ask for:

• SHBG level (blood test)
• Total testosterone (blood test)
• Calculated free testosterone (derived from total testosterone + SHBG)
• Fasting insulin and glucose (to assess insulin resistance)
• TSH, free T3, free T4 (to assess thyroid function)

Red flags requiring medical attention:

• Severe depression or suicidal thoughts (hormone-related or not, requires urgent care)
• Sudden, severe symptoms (severe acne, rapid hair growth, voice deepening) → may indicate adrenal tumor or other serious condition
• Signs of thyroid storm (hyperthyroidism crisis: rapid heart rate, fever, confusion) → medical emergency
• Signs of diabetic emergency (very high blood sugar, excessive thirst, frequent urination, confusion)

Work with a knowledgeable clinician:

• Endocrinologist → hormone specialist, experienced in interpreting SHBG and free hormone levels
• Integrative or functional medicine doctor → often more proactive about testing SHBG and addressing root causes (insulin resistance, thyroid dysfunction)
• Menopause specialist → experienced in hormone therapy optimization, including SHBG considerations

Advocacy tip:

Many conventional doctors don't routinely test SHBG or free testosterone. If your doctor is dismissive ("your labs are normal"), you can:

1. Explain your symptoms clearly → low libido, fatigue, acne, hair growth (whatever applies)
2. Request SHBG testing specifically → "I'd like to understand my free testosterone, not just total testosterone. Can we test SHBG?"
3. Bring research → studies showing that free testosterone correlates better with symptoms than total testosterone
4. Seek a second opinion → if your doctor refuses to test or dismisses your concerns, find a clinician who takes hormone symptoms seriously

You deserve to have your symptoms taken seriously. SHBG testing is simple, inexpensive, and can provide the missing piece to understanding why you feel the way you do.

Related Terms

• testosterone
• estrogen
• insulin
• insulin-resistance
• free-testosterone
• libido
• acne
• facial-hair
• hair-loss
• fatigue
• androgen-dominance
• thyroid
• hrt-hormone-replacement-therapy
• metabolic-syndrome