Plasma Sex Hormone-Binding Globulin Binding Capacity in Benign Prostatic Hypertrophy and Prostatic Carcinoma: Comparison With an Age Dependent Rise in Normal Human Males

Abstract

A method for the routine determination of plasma sex hormone-binding globulin (SHBG) binding capacity is introduced. In normal males an age dependent increase in SHBG binding capacity from 2.85 \ m=x\ 10\m=-\8 m in the age range 22\p=n-\44 years to 4.66 \m=x\ 10\m=-\8m in the age range 45\p=n-\64 years was found. A higher mean value of 6.41 \ m=x\ 10\m=-\8m was obtained in normal females, 20\p=n-\40 years old, and still higher values were found in females taking oral contraceptives. Although in male groups with benign prostatic hypertrophy or prostatic carcinoma the mean ages were somewhat higher than in the older normal group, a further age dependent increase in SHBG binding capacity in these diseases could not be demonstrated. In fact the mean values found were slightly although not significantly lower at 4.07 and 3.89 \m=x\ 10\ m=-\ 8 m, respectively. As expected, oestrogen treatment of males with prostatic carcinoma produced higher values.The importance of the binding of sex steroids, particularly the androgens, testosterone, and 5a-dihydrotestosterone (5a-DHT) to sex hormone-binding globulin (SHBG) in human plasma has been demonstrated in relation to uptake by target organs (Lasnitzki 8c Franklin 1975), influence on "free" steroid con¬ centrations (Rosenfield 1971;Vermeulen et al. 1969) and metabolic clearance Supported by the DFG, Sonderforschungsbereich 34 (Endocrinology).

Quantitative Determination of the Binding Capacity of the Sex Hormone-Binding Globulin, Using Agar Gel Electrophoresis

“…The validity has been shown by the significant correlation of the data with the values obtained according to Dennis et al (15), as well as by the comparison of normal ranges of SHBGbinding capacities in male plasma (table 1) ; The values of Wagner &Ruffert (12), also using agargel electrophoresis, are remarkably high. The main reason for this difference from our values might be that background subtraction has not been performed by these authors.…”

“…The increase of the SHBG-binding capacity in elderly men has been described by various authors (15,21,22). Consequently, the percentage binding of testosterone to SHBG (23) will increase, amplified by the slightly lower testosterone plasma levels in elderly men (22).…”

“…Due to the lack of purified SHBG, accuracy could not be determined. An indirect evaluation of the accuracy of the method is shown in figure 7, where 10 male plasma samples were simultaneously analyzed by agar gel electrophoresis and by a method first described by Dennis et al from this laboratory (15).…”

“…Furthermore, charcoal might eliminate small amounts of SHBG itself from the incubation medium(13), thus masking the possible rise of the binding capacity. However, as shown by Dennis et al(15), the loss of SHBG by charcoal adsorption is extremely low. In contrast to the procedure of Wagner &Ruffert (12), we have introduced a competition step for quantifying the SHBG-binding capacity.…”

“…If this background is not subtracted the actual SHBG-binding capacity would rise artificially. It should be noted that the displacement curve offigure 1often displays a shoulder in slice numbers[15][16][17][18], indicating that small amounts of [ 3 H]DHT remain bound to SHBG. However, for routine determination of the binding capacity, this amount (less than 5% of the total SHBG) can be neglected.…”