Significant ethnic variation in total and free testosterone concentration

Area of Science:

• Endocrinology
• Metabolic Health
• Population Health

Background:

• Serum testosterone measurement is crucial for assessing male endocrine health.
• Ethnic variations in testosterone bioavailability and their determinants are not well understood.
• Sex hormone-binding globulin (SHBG) influences testosterone bioavailability and is linked to insulin sensitivity.

Purpose of the Study:

• To investigate ethnic differences in serum testosterone and SHBG levels.
• To examine the relationship between these hormone levels and insulin sensitivity across ethnic groups.
• To determine if ethnic variations in testosterone are linked to insulin sensitivity.

Main Methods:

• A study involving men from White European, Pakistani, and African-Caribbean ethnic groups in Manchester, UK.
• Measurement of serum total testosterone, SHBG, and calculation of free testosterone.
• Assessment of insulin sensitivity (HOMA-S) and insulin secretory capacity (HOMA-B) using fasting glucose and insulin levels.

Main Results:

• Pakistani men had significantly lower total and free testosterone levels compared to European and African-Caribbean men.
• Lower SHBG levels were observed in Pakistani men, correlating with poorer insulin sensitivity (HOMA-S).
• Total testosterone was independently associated with fasting insulin, age, SHBG, and height, but not ethnicity or waist-hip ratio.

Conclusions:

• Pakistani men show reduced levels of both total and free testosterone.
• Lower SHBG in Pakistani men is consistent with their poorer insulin sensitivity.
• Ethnic-specific reference ranges for testosterone interpretation in men are recommended.