Age Related Changes and Interrelationships Between Plasma Testosterone, Oestradiol and Testosterone-Binding Globulin in Normal Adult Males

Testosterone (T), oestradiol-17β (Oe 2 ) and binding capacity of the testosterone-binding globulin (TeBG) were measured in plasma of 84 adult males (22–90 years). The medians for age group I (22– 61 years, n = 50) were: T 545 ng/100 ml, Oe 2 1.66 ng/100 ml, TeBG capacity 1.44 μg T/100 ml; the medians for age group II (67–90 years, n = 34) were: T 459 ng/100 ml, Oe 2 2.56 ng/100 ml, TeBG capacity 2.05 μg T/100 ml. The decrease of T and the increase of Oe 2 and TeBG capacity with age were significant. The significant correlation ( P < 0.01) for either age group between T and Oe 2 may be ascribed to a simultaneous secretion and/or a peripheral conversion of T to Oe 2 . The significant correlation ( P < 0.05) between T and TeBG for the old age group probably reflects the comparatively high percentage of total plasma T bound to TeBG. The biological meaning of the correlation between Oe2 and TeBG is discussed.