Significance of Elevated SHBG with Normal Testosterone Levels
Elevated Sex Hormone Binding Globulin (SHBG) with normal total and free testosterone levels indicates adequate bioavailable testosterone and does not require clinical intervention in most cases.
Understanding the Laboratory Values
- Total testosterone of 535 ng/dL is within normal range (250-827 ng/dL)
- Free testosterone of 48.9 pg/mL is within normal range (46.0-224.0 pg/mL)
- SHBG of 52 nmol/L is slightly elevated (normal range: 10-50 nmol/L)
- Albumin of 4.5 g/dL is normal (3.6-5.1 g/dL) 1
Clinical Significance of Elevated SHBG
Mechanism and Impact
- SHBG is the major serum carrier of sex hormones, binding to testosterone with high affinity 2
- Elevated SHBG can potentially reduce bioavailable testosterone by increasing the bound fraction 2
- However, when free testosterone remains normal (as in this case), adequate hormone is available to tissues despite elevated SHBG 1
Clinical Implications
- Normal free testosterone level (48.9 pg/mL) indicates that despite elevated SHBG, there is sufficient unbound testosterone available for biological activity 1
- When evaluating testosterone status, free testosterone measurement is essential, especially when SHBG levels are abnormal 1
- Morning free testosterone by equilibrium dialysis is the most reliable measure of bioactive testosterone when SHBG is abnormal 1
Potential Causes of Elevated SHBG
- Estrogen exposure or increased estrogen activity 2
- Thyroid hormone excess (hyperthyroidism) 2
- Advanced age (SHBG tends to increase with aging) 3
- Liver disease 2
- Certain medications (especially estrogens) 2
- Low body mass index or reduced adiposity 1
- Low insulin levels (SHBG correlates negatively with insulin levels) 2
Clinical Assessment Recommendations
- Since both total and free testosterone levels are normal, no specific treatment for the elevated SHBG is required 1
- Consider evaluating thyroid function if not recently checked, as thyroid disorders can affect SHBG levels 2
- Monitor for symptoms of androgen deficiency despite normal laboratory values, including:
- Decreased energy, libido, muscle mass, or body hair
- Hot flashes, gynecomastia, or infertility 1
- If symptoms of hypogonadism are present despite normal laboratory values, repeat testing may be warranted 1
When Further Evaluation Is Needed
- If clinical symptoms of hypogonadism develop, repeat morning testosterone measurements 1
- If testosterone levels become subnormal on repeat testing, measure luteinizing hormone (LH) and follicle-stimulating hormone (FSH) to distinguish primary from secondary hypogonadism 1
- Consider additional evaluation for causes of elevated SHBG if clinically indicated based on symptoms 2
Common Pitfalls to Avoid
- Focusing solely on total testosterone without considering free testosterone levels when SHBG is abnormal 1
- Initiating testosterone therapy based on a single borderline test result 4
- Failing to consider diurnal variation in testosterone levels (samples should be collected in the morning) 5
- Overlooking that laboratory reference ranges for testosterone may vary by age 3
- Treating laboratory values rather than clinically significant symptoms 4