What is the normal Sex Hormone-Binding Globulin (SHBG) level for a 65-year-old?

Normal Sex Hormone-Binding Globulin (SHBG) Levels for a 65-Year-Old

For a 65-year-old, the normal SHBG reference range is approximately 20-60 nmol/L, with significant individual variation possible based on health status and other factors.

Age-Related Changes in SHBG

SHBG levels naturally increase with age, particularly in men. Research shows a significant difference between younger and older men:

• In men ≤54 years old: mean SHBG is 27.7±13.3 nmol/L (range 6-88) 1
• In men ≥55 years old: mean SHBG is 36.6±15.8 nmol/L (range 11-109) 1

This represents a statistically significant increase in SHBG levels with advancing age (p<0.001).

Factors Affecting SHBG Levels

Several factors can influence SHBG levels in older adults:

• Obesity/Body Fat: Higher BMI and percentage body fat are associated with lower SHBG levels 2
• Metabolic Factors: Conditions like diabetes, metabolic syndrome, and insulin resistance typically lower SHBG levels 2
• Medications: Certain medications including exogenous testosterone can decrease SHBG levels 3
• Thyroid Function: Hypothyroidism can affect SHBG levels

Clinical Implications of SHBG Levels

SHBG is clinically important because:

1. Testosterone Bioavailability: SHBG binds tightly to testosterone, making the bound portion biologically unavailable. Only free and albumin-bound testosterone (bioavailable testosterone) are accessible to tissues 4

2. Cardiovascular Risk: Higher SHBG levels have been associated with increased cardiovascular disease risk in men, particularly those over 65 years old 5

3. Hypogonadism Assessment: When evaluating testosterone levels, SHBG measurement is essential for proper interpretation:

   • In men with diabetes who have symptoms of hypogonadism (decreased libido or erectile dysfunction), morning total testosterone should be measured 6
   • For men with total testosterone levels close to the lower limit, SHBG testing should be considered as it is often low in diabetes and associated with lower testosterone levels 6

Interpretation Guidelines

When interpreting SHBG results:

• The remarkably wide distribution of SHBG concentrations (nearly 20-fold difference between lowest and highest values) means that individual variation is substantial 1
• About 9% of men ≥55 years old have SHBG >60 nmol/L 1
• Values should be interpreted in the context of clinical symptoms and total testosterone levels
• Calculated bioavailable testosterone depends on accurate SHBG values and appropriate association constants 4

Clinical Application

For a 65-year-old with suspected testosterone deficiency:

1. Measure morning total testosterone level
2. Measure SHBG level to properly interpret testosterone results
3. Consider symptoms such as decreased sexual desire or erectile dysfunction
4. Evaluate for other conditions that might affect SHBG (diabetes, obesity, thyroid disorders)

Remember that SHBG levels should be interpreted as part of a comprehensive hormone evaluation rather than in isolation.