Can high SHBG and low total Testosterone cause Erectile Dysfunction?

Your High SHBG is Likely Contributing to Your ED Despite Normal Total Testosterone

With an SHBG of 99 nmol/L (nearly double the upper normal limit) and a total testosterone of 35 nmol/L (~1000 ng/dL), you likely have functional hypogonadism—your free testosterone is probably low despite the seemingly adequate total testosterone, and this can absolutely cause erectile dysfunction. 1

Why This Matters for Your ED

Your elevated SHBG binds most of your testosterone, rendering it biologically inactive—only free testosterone can enter tissues and exert physiological effects necessary for erectile function 1. The European Association of Urology recognizes that SHBG elevation causes symptomatic androgen deficiency even when total testosterone appears normal or high, leading to low libido and erectile dysfunction 2, 1.

The Free Testosterone Problem

• Total testosterone is misleading in your case: With SHBG at 99 nmol/L, approximately 17% of men with ED and normal total testosterone actually have low free testosterone that causes symptomatic hypogonadism 3
• Your free testosterone index (total T/SHBG ratio) is approximately 0.35, which is borderline for functional hypogonadism (ratios <0.3 indicate functional hypogonadism) 1
• Free and bioavailable testosterone are inversely associated with ED severity, while total testosterone shows obscure or even paradoxically positive associations due to SHBG elevation 4, 5

What You Need to Do Next

Essential Diagnostic Steps

1. Measure calculated free testosterone immediately using equilibrium dialysis or calculation from total testosterone, SHBG, and albumin—this is critical because total testosterone alone misses approximately half of diagnoses when SHBG is elevated 2, 1, 3

2. Repeat testing with morning blood draws to confirm the pattern, as single measurements can be misleading 1

3. Investigate causes of your elevated SHBG 2, 1:

   • Check thyroid function (TSH, free T4) for hyperthyroidism
   • Review medications (anticonvulsants, oral estrogens increase SHBG)
   • Liver function tests (ALT, AST, albumin) to exclude chronic liver disease
   • Consider age-related SHBG elevation if you're over 60 years old

Treatment Algorithm

First-line approach (address reversible causes) 1:

• Treat hyperthyroidism if present
• Discontinue SHBG-elevating medications if possible
• Optimize metabolic health and body composition

Second-line approach (if free testosterone confirmed low after addressing reversible causes) 1:

• Testosterone replacement therapy can improve erectile function with moderate-certainty evidence, producing small to moderate improvements 2, 1
• Transdermal preparations are preferred for most patients 1
• Monitor free testosterone levels 2-3 months after initiation 1

Concurrent ED management 6, 7:

• PDE5 inhibitors (sildenafil, tadalafil, vardenafil) remain first-line for ED regardless of testosterone status 2
• If you're already taking PDE5 inhibitors without adequate response, testosterone replacement can convert over half of hypogonadal non-responders into responders 6

Critical Pitfalls to Avoid

• Don't rely on total testosterone alone to exclude hypogonadism—current screening recommendations miss functional hypogonadism in patients with elevated SHBG, especially those over 60 years old 3
• Don't assume normal total testosterone means normal androgen function when SHBG is elevated—the bioactive free testosterone is what matters for erectile physiology 1, 4
• Don't start testosterone replacement without confirming low free testosterone first—you need objective confirmation before committing to long-term therapy 2, 1