To establish a set of population derived reference ranges for plasma total testosterone, sex hormone binding globulin (SHBG) and calculated free testosterone (FT) values especially in older men.
The age-related decline in testosterone concentrations in men is gradual and both cross-sectional and longitudinal data have shown that there was a small but significant decline in total and free testosterone concentrations from the fifth decade onwards. As most circulating testosterone (98%) is bound to SHBG and albumin, various mathematical equations have been used to calculate free testosterone levels.
We undertook a cross-sectional study of 184 predominantly older healthy men (age range 2089, mean age 52 years) recruited from outpatient clinics with local ethical approval. Plasma testosterone concentrations were measured on the ADVIA Centaur (Bayer) and SHBG on the Immulite 2000 (DPC). FT values were calculated using the Sodergard, Vermeulen, Nanjee-Wheeler and Carter equations.
Reference ranges (95th centile) of plasma testosterone, SHBG and calculated free testosterone (FT) values were as follows :
|Patient age group||Total Testosterone nmol/l||SHBG nmol/l||FT (Sodergard) nmol/l||FT (Vermeulen) nmol/l||FT (Nanjee-Wheeler) nmol/l||Free Androgen Index|
|2039 years n=50||12.426.4||11.753.4||0.2360.680||0.1900.665||0.2560.716||29.0140.6|
|4089 years n=134||4.924.4||18.067.0||0.1170.558||0.0920.552||0.1310.580||14.489.7|
There is a significant difference (P<0.05) between the measured plasma total testosterone and the various calculated FT values between the younger men (<40 years old) and older men (>40 years old) group.
This study provides a set of useful data for age-related reference ranges for total testosterone and calculated FT. The calculated FT is especially useful when the measured plasma testosterone is borderline low (between 712 nmol/l) in the investigations of older patients presenting with andropause symptoms.
06 - 07 Nov 2006
Society for Endocrinology