title: Study on the binding of dihydrotestosterone, testosterone and oestradiol with sex hormone binding globulin.
abstract: Saturation studies on sex hormone binding globulin (SHBG) were performed with increasing levels of the three steroids: dihydrotestosterone (DHT), testosterone (T) and oestradiol (E2) in normal female sera. The curves obtained showed the clearly increasing SHBG affinity for E2, T and DHT, respectively. With T as saturating ligand, the mean values of SHBG binding capacity in normal and pathological sera, expressed as 10(-8) M SHBG were, for normal women, 5.87 +/- 0.2, for normal men, 3.69 +/- 0.1 and for hirsute women, 5.05 +/- 0.2. In hirsutism, SHBG levels were measured together with T and DHT levels. Hyperandrogenia was often better reflected by the T/SHBG ratio than by T levels alone. SHBG binding capacity, measured in pregnancy from the 7th to the 40th week, increased progressively as far as the 30th week. Values up to 5 times those of the mean value of the cycle were observed at the end of pregnancy. Variations in DHT, T and E2 binding as functions of SHBG concentrations, were also studied by adding a constant amount of each steroid to increasing SHBG concentrations in serum. DHT showed the greatest binding capacity, followed by T and then E2. Since the unbound fractions of T and DHT are believed to be biologically active, and since T and DHT are more sensitive than E2 to SHBG variations, the results obtained further support the hypothesis that SHBG plays an important role in the sex steroids balance.
mesh_terms: D000568:Amenorrhea / Q000097:blood; D013196:Dihydrotestosterone / Q000097:blood*; D004958:Estradiol / Q000097:blood*; D005260:Female; D006628:Hirsutism / Q000097:blood; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D011247:Pregnancy; D011485:Protein Binding; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism*; D013739:Testosterone / Q000097:blood*; D013997:Time Factors
chemical_list: D012738:Sex Hormone-Binding Globulin; D013196:Dihydrotestosterone; D013739:Testosterone; D004958:Estradiol