SERUM AND FOLLICULAR-FLUID SEX HORMONE-BINDING GLOBULIN IN STIMULATEDAND UNSTIMULATED CYCLES

It is well-known that sex hormone-binding globulin (SHBG) concentratio ns in the follicle are relatively low in comparison with the correspon ding estradiol (E(2)) levels, which are extremely high. A direct compa rison of these data in stimulated and unstimulated cycles, as well as the relationship of SHBG with testosterone (T) and E(2) in serum and f ollicular fluid (FF), is assessed. Methods: SHBG was measured in serum and FF in 42 cycles stimulated by GnRH agonists and gonadotropins and in 15 unstimulated cycles. The levels of SHBG, were compared to the c orresponding total estradiol and total testosterone concentrations. Th e analyzed FFs of 42 women, 12 of whom conceived, were randomly select ed from 90 patients participating in an in vitro fertilization program . Mature oocytes were retrieved from all follicles from which FFs were analyzed. Results: Markedly elevated SHBG was found in both the serum and the FF of stimulated cycles compared to unstimulated cycles. In c ontrast, serum T and E(2) were significantly higher in induced than in unstimulated cycles, while there was no significant difference in FF T or E(2) between the two groups of cycles. No correlation was found b etween serum and FF SHBG in either stimulated or unstimulated cycles. In stimulated cycles, only in FF, SHBG was significantly correlated wi th both E(2) and T. In unstimulated cycles, no correlation was found b etween SHBG and either one of the corresponding steroids either in ser um or in FF. Conclusions: The fraction of non-SHBG bound, biologically active sex steroids may be lower in the FF of stimulated than that of unstimulated cycles.