Should I be experiencing low libido with high Sex Hormone-Binding Globulin (SHBG) and high total testosterone levels?

High SHBG with High Total Testosterone and Low Libido

Yes, you can absolutely experience low libido despite high total testosterone (40 nmol/L) when SHBG is elevated (95 nmol/L), because what matters for sexual function is your free (bioavailable) testosterone, not total testosterone. 1

Understanding the Problem

Your situation represents a critical disconnect between total and free testosterone:

• SHBG binds to testosterone and makes it biologically inactive—the higher your SHBG, the less free testosterone is available to act on tissues including the brain centers that regulate libido 1
• Free testosterone is the bioactive form that actually drives sexual function, and with SHBG at 95 nmol/L (reference range typically 7-50 nmol/L), a significant portion of your total testosterone is bound and unavailable 2
• The free testosterone index (total testosterone/SHBG ratio) is more predictive of hypogonadal symptoms than total testosterone alone; a ratio <0.3 indicates functional hypogonadism 1

In your case: 40 nmol/L ÷ 95 nmol/L = 0.42, which is borderline low and can absolutely cause symptoms despite seemingly adequate total testosterone.

Why This Causes Low Libido

Free testosterone levels correlate significantly with libido, erectile function, and other sexual symptoms, whereas total testosterone alone does not reliably predict these symptoms 2:

• Studies demonstrate that men with sexual symptoms and low calculated free testosterone (<63 pg/mL or ~2.2 nmol/L) experience reduced libido even when total testosterone appears normal 2
• Reduced libido is one of the most specific symptoms of hypogonadism, more predictive than physical or psychological symptoms 1
• The brain receptors that regulate sexual desire respond to free testosterone, not bound testosterone 3

Diagnostic Confirmation

You need to measure your calculated free testosterone to confirm functional hypogonadism 2:

• Request morning blood draw (8-10 AM) for total testosterone, SHBG, and calculated free testosterone 1, 4
• Repeat testing to confirm the pattern, as single measurements can be misleading 4
• Free testosterone <63 pg/mL (2.2 nmol/L) confirms hypogonadism despite normal total testosterone 2

Common Causes of Elevated SHBG

Investigate these potential underlying causes 4:

• Hyperthyroidism (thyroid hormone increases SHBG production)
• Liver disease (altered hepatic SHBG synthesis)
• Aging (SHBG naturally increases with age)
• Medications including oral estrogens, anticonvulsants
• Low insulin states (in contrast to obesity/metabolic syndrome which lowers SHBG)

Management Approach

If free testosterone is confirmed low, treatment options depend on the underlying cause 1:

First-Line: Address Underlying Causes

• Treat hyperthyroidism if present (normalizing thyroid function can reduce SHBG) 4
• Discontinue medications that increase SHBG if possible 4
• Optimize metabolic health through diet and exercise 4

Second-Line: Testosterone Replacement

If free testosterone remains low after addressing reversible causes, testosterone therapy improves sexual function with moderate-certainty evidence 1:

• Testosterone treatment produces small to moderate improvements in global sexual function (effect size 0.35) and erectile function (effect size 0.27) 1
• The Testosterone Trials demonstrated clinically meaningful improvements in sexual desire (effect size 0.44) and sexual activity (effect size 0.45) 1
• Transdermal or intramuscular testosterone are both effective, with similar outcomes 1

Critical Caveat

Exogenous testosterone can paradoxically worsen the situation if it further suppresses SHBG 5, 6:

• Some testosterone formulations, particularly when combined with certain oral androgens, can decrease hepatic SHBG synthesis 5
• Monitor SHBG and free testosterone levels 3 months after starting therapy, then every 6-12 months 4

Bottom Line

Your low libido is entirely consistent with elevated SHBG reducing your bioavailable testosterone. Get your free testosterone measured—if it's low (<63 pg/mL), you have functional hypogonadism that warrants treatment regardless of your total testosterone level. 2