Can low SHBG make total testosterone look lower without lowering free testosterone?

At age 50, a low total testosterone result deserves interpretation in the context of SHBG rather than automatic classification as androgen deficiency. This is particularly relevant in obesity, insulin resistance, or type 2 diabetes, which are commonly associated with lower SHBG.

Clinical evidence

• SHBG binds testosterone with high affinity; only about 1–4% circulates as free testosterone. When SHBG falls, the SHBG-bound pool—and therefore measured total testosterone—can fall while free testosterone remains preserved.
• In the European Male Ageing Study, 96 men had low total testosterone but normal calculated free testosterone. They were more obese and did not show associated androgen-deficiency symptoms.
• In obese versus non-obese men, lower mean SHBG and total testosterone occurred without a difference in mean calculated free testosterone; calculated free testosterone correlated strongly with equilibrium-dialysis/tandem-MS measurement.
• In EMAS, total-testosterone criteria classified 36% of men as hypogonadal versus 15% using free-testosterone criteria. Men with low total but normal free testosterone had symptom scores comparable to men with normal free testosterone.

Mechanistic and testing implications

• Reduced SHBG lowers the circulating protein-bound testosterone reservoir, explaining why total testosterone may underestimate biologically available androgen exposure in low-SHBG states.
• Endocrine Society guidance supports fasting morning total-testosterone testing on two separate occasions, followed—when total testosterone is borderline or SHBG is likely abnormal—by equilibrium-dialysis free testosterone or an accurate calculated free testosterone using total testosterone, SHBG, and albumin.
• Direct analog free-testosterone immunoassays should not be used because of inaccuracy. Results also require assay- and method-specific reference ranges and correlation with compatible symptoms/signs.

Bottom line

• The claim is well supported: low SHBG can produce low measured total testosterone without low free testosterone, so total testosterone alone can overstate androgen deficiency in low-SHBG contexts.