Sex Hormone Binding Globulin Binding Capacity Research Articles

Higher Maternal Levels of Free Estradiol in First Compared to Second Pregnancy: Early Gestational Differences<xref ref-type="fn" rid="FN2">2</xref>

Serum samples drawn from 34 women in the early part of both their first and their second pregnancies were assayed for estradiol (E2), percentage of free E2, and sex hormone-binding globulin-binding capacity (SHBG-bc). Subjects were participants in the Collaborative Perinatal Study conducted by the National Institute of Neurological and Communicative Disorders and Stroke (Bethesda, MD) to evaluate factors related to adverse pregnancy outcome. All pregnancies were full term, and no offspring had a congenital malformation. After adjustment for week of pregnancy, the percentage of free E2 was 9% higher (two-sided P = .007) and the amount of free E2 was 17% higher (two-sided P = .03) in first-pregnancy sera. Total E2 was also 7% higher in first-pregnancy sera after adjustment for week of pregnancy; SHBG-bc was 7% lower after adjustment for week of pregnancy and 9% lower after simultaneous adjustment for week of pregnancy and weight at the start of pregnancy; but these differences were not statistically significant. These findings confirm our previously published hypothesis that the early part of a woman's first pregnancy differs endocrinologically from her second and may provide further insight into pregnancy-related risk factors for testis cancer and cryptorchidism and into the protection afforded by first full-term pregnancy against breast cancer.

Biochemical basis for the antagonism between aminoglutethimide and danazol in the endocrine treatment of breast cancer.

Only 13% of postmenopausal advanced breast cancer patients responded to endocrine treatment with aminoglutethimide plus danazol whilst 33% responded to aminoglutethimide alone, despite a similar suppression of serum oestradiol levels in the two groups. The patients on aminoglutethimide and danazol showed a marked suppression of sex hormone binding-globulin binding capacity and a consequent rise in percent-free oestradiol. This led to the concentration of free oestradiol being less well suppressed than that of total oestradiol and in some patients free oestradiol concentrations were higher on treatment than before. Patients on aminoglutethimide alone showed no change in the binding of oestradiol and the percentage suppression of the free oestradiol concentration was similar to that of total oestradiol. The opposing effects of danazol and aminoglutethimide on the concentration of the free, biologically active fraction of oestradiol in the circulation may explain the poor therapeutic efficacy of this combination in breast cancer patients.

Non-sex hormone-binding globulin-bound testosterone as a marker for hyperandrogenism.

Recent evidence suggests that the biologically active testosterone includes both the free and albumin-bound fractions, while the sex hormone-binding globulin (SHBG)-bound steroid dissociates less readily. To examine the significance of the non-SHBG-bound testosterone (i.e. free plus albumin bound) in hyperandrogenism, we obtained single blood samples from 17 normal women, 20 regularly menstruating but hirsute women, and 20 oligoamenorrheic hirsute women. Each serum sample was analyzed for total testosterone by RIA, SHBG-binding capacity was determined by protein precipitation with 50% saturated (NH4)2SO4, and albumin was measured by colorimetry. Non-SHBG-bound and free testosterone and the testosterone to SHBG molar ratio were then calculated. Non-SHBG-bound testosterone was also assayed using differential protein precipitation. There were significant differences among the groups in the mean values of all variables (all P less than 0.05) except albumin. Measurement and calculation of serum non-SHBG-bound testosterone produced similar results, suggesting that the binding equation is valid. There was considerable overlap between normal (control mean +/- 2 SD) and abnormal subjects in all variables except non-SHBG-bound testosterone, for which only 3 regularly menstruating and 2 oligoamenorrheic hirsute subjects were in the normal range. As total testosterone levels increased, there was a significant increase in the ratio of non-SHBG-bound testosterone to free testosterone. These data suggest that albumin becomes increasingly more important in testosterone binding as the total serum testosterone level increases and that non-SHBG-bound testosterone may be the optimal marker to identify hyperandrogenism in hirsute women.

Oestrogen-related changes in sex hormone binding globulin levels during normal and gonadotrophin-stimulated menstrual cycles.

Previous studies have identified no consistent change in sex hormone binding globulin (SHBG) levels during normal menstrual cycles. This is despite marked cyclical changes in plasma oestradiol concentration, and the observation that SHBG level increases in pregnancy, and after administration of exogenous gonadotrophin or synthetic oestrogens. The level of SHBG was measured in 19 normal females at 2 d intervals from day -8 to +10 where the preovulatory peak of oestradiol was designated as occurring on day 0. SHBG levels increased by a mean 15% +/- 4 (SEM) between the follicular and luteal phases (P less than 0.001) and this was due entirely to an increment between day 0 and +2. The change in SHBG levels was correlated with the change in oestradiol levels between days -8 and 0 (P less than 0.001). Fifty-six infertile patients were also studied. Twenty-seven received Pergonal alone whilst the other 29 received Pergonal after a preceding 5 d on Clomid. In both groups peak preovulatory oestradiol levels were greater than 3 times higher than in normal cycles. SHBG levels showed no change in the follicular phase but rose markedly during the luteal phase. These increases were significantly correlated with peak preovulatory oestradiol concentration but showed no relationship with mid-luteal progesterone concentration. We conclude that supranormal levels of oestradiol cause marked increases in SHBG binding capacity and increases in SHBG level of a lower order occur shortly after the preovulatory peak of oestradiol in the normal menstrual cycle.

The distribution of oestradiol in plasma from postmenopausal women with or without breast cancer: Relationships with metabolic clearance rates of oestradiol

The distribution of oestradiol in plasma from postmenopausal women with or without breast cancer has been measured and related to the metabolic clearance rates of oestradiol (MCR-E2). All measurements were carried out preoperatively. No difference in the free fraction of oestradiol was found between women with breast cancer (1.8 +/- 0.4%, mean +/- SD) and normal women (1.6 +/- 0.3%). Approximately 40% of oestradiol in plasma was bound to albumin with 60% bound to sex hormone binding globulin (SHBG), but values were similar for women with or without breast cancer. Concentrations of total unconjugated oestradiol and free oestradiol (2.4 +/- 0.5 ng/100 ml and 44 +/- 12 pg/100 ml respectively, mean +/- SD, n = 9) were significantly higher in plasma from postmenopausal women with breast cancer compared with levels in plasma from normal postmenopausal women (1.8 +/- 0.5 ng/100 ml and 27 +/- 10 pg/100 ml, n = 8). A significant correlation was found between the free oestradiol fraction and MCR-E2 (r = 0.53, p less than 0.05). Correlations were also found between the fractions of oestradiol bound to albumin and MCR-E2 (r = 0.45). From correlations between the binding capacity of SHBG and MCR-E2 it appears that, for a given level of SHBG, MCR-E2 may be higher in women with breast cancer.

Changes in sex hormone-binding globulin binding capacity and percent free estradiol during development in the female rhesus monkey (Macaca mulatta): relation to the metabolic clearance rate of estradiol.

Circulating sex hormone-binding globulin (SHBG) binding capacity and percent free estradiol (% free E2) were measured in separate groups of female rhesus monkeys from 2 months of age through adulthood (greater than 4.5 yr old). The SHBG concentration alone was also measured in 11 adult and 6 sexually immature animals on the same day as the blood MCR of E2. Serum SHBG levels were the highest (range, 12-25 micrograms T/dl) and the % free E2 the lowest (0.88%) in animals 6 months old or less. After the age, serum SHBG binding capacity declined generally at an average rate of 0.11 SHBG U (microgram T/dl)/month toward a nadir in adulthood. There was no difference in the SHBG levels in the follicular or luteal phase of the menstrual cycle. The relative blood MCR E2 and circulating SHBG binding capacity were significantly greater (P less than 0.001) in the sexually immature animals [MCR E2, 48.4 +/- 5.2 (SEM) liters/day . kg body wt; SHBG, 9.8 +/- 1.0 microgram T/dl, n = 6] than in adult animals (MCR E2, 27.7 +/- 1.7 liters/day kg body wt; SHBG, 4.6 +/- 0.3 microgram T/dl, n = 11). There was no relation between the MCR E2 and circulating SHBG levels within each group of adult or immature animals. The mean % free E2 doubled (to 1.6%) between 1 and 54 months of age; there was no relation between total circulating E2 and % free E2. Although a high SHBG binding capacity and a low % free E2 in the circulation of the immature animal does not inhibit the metabolic clearance of E2; it remains possible that these factors (and others) may hinder the access of E2 to reproductive target tissues and thereby contribute to the slow acquisition of reproductive competence in this species.

Comparison of hepatic impact of oral and vaginal administration of ethinyl estradiol

The pronounced hepatic impact of oral ethinyl estradiol has been attributed by some to its so-called first-pass effect through the liver as only some 40% of ingested ethinyl estradiol reaches the systemic circulation. Others believe that ethinyl estradiol exerts its hepatic effects of its chemical composition, specifically its 17α-ethinyl group. In an attempt to resolve this controversy, a study was undertaken to determine whether vaginal administration of ethinyl estradiol can selectively reduce the hepatic effects of oral ethinyl estradiol. To compare the effects of oral and vaginal ethinyl estradiol, a group of postmenopausal subjects received either 5 μg of oral and 20 μg of vaginal ethinyl estradiol or 10 μg of oral and 50 μg of vaginal ethinyl estradiol in either sequence, respectively. Oral ethinyl estradiol was four to five times more potent than vaginal ethinyl estradiol. The potency ratios of the oral-vaginal ethinyl estradiol doses required to suppress follicle-stimulating hormone and luteinizing hormone were 4.4 and 3.2 and those to raise sex hormone-binding globulin binding capacity, corticosteroid-binding globulin binding capacity, and high-density lipoprotein cholesterol as well as lower low-density lipoprotein cholesterol were 3.5, 5.0, 4.2, and 4.2, respectively. These essentially equal oral-vaginal route potency ratios for both central nervous system and hepatic effects indicate that vaginal administration of ethinyl estradiol does not selectively reduce its hepatic impact in relation to its central nervous system effects. The pronounced hepatic effects of ethinyl estradiol are therefore attributed to its chemical composition.

Daily variations of plasma sex hormone-binding globulin binding capacity, testosterone and luteinizing hormone concentrations in healthy rested adult males.

In this study the daily variations of plasma sex hormone-binding globulin (SHBG) binding capacity were measured together with plasma testosterone and luteinizing hormone (LH) concentrations in 7 healthy rested adult males. Plasma SHBG-binding capacity demonstrated a significant circadian rhythm (acrophase = 2.06 p.m.; mesor = 0.35 +/- 0.6 ng testosterone bound/100 ml; amplitude = 17% of the mesor). Plasma testosterone also showed a circadian rhythm (acrophase = 7.02 a.m.; mesor = 4.38 +/- 0.67 ng/ml; amplitude = 18% of the mesor). The free testosterone index (or the ratio between plasma testosterone and SHBG-binding capacity) was not correlated with plasma LH levels. In our hands this last parameter did not vary according to a circadian pattern. These data are discussed in terms of a feedback mechanism controlling the pituitary-testis axis regulation.

Serum levels of unbound 17 beta-oestradiol during oral and percutaneous postmenopausal replacement therapy.

The metabolic effects of oestrogen therapy are influenced by the route of administration. Compared with oral treatment, percutaneous administration may have theoretical advantages with respect to liver metabolism, but there are also potential disadvantages related to the specific kinetics of this route. The increase of SHBG binding capacity is much less pronounced, which might result in excess amounts of unbound, biologically-active steroid during therapy. The serum concentrations of unbound 17 beta-oestradiol were calculated in two groups of postmenopausal women during replacement therapy with equivalent amounts of oral and percutaneous oestrogen. A highly significant and quite similar increase of the free fraction as well as in total 17 beta-oestradiol was found in both groups of women, in spite of the fact that SHBG binding capacity was unchanged during percutaneous therapy. Albumin binding and the total serum concentration of 17 beta-oestradiol were found to be more important for the regulation of unbound steroid concentration than variations in SHBG binding capacity. In conclusion, there was no evidence that percutaneous administration per se would carry an increased risk of over-treatment.

Haemodialysis and testicular function.

Gonadal dysfunction in men with chronic renal failure is well established. However, the effect of haemodialysis on the function of the testis has not been studied in detail, so we have investigated the effect of haemodialysis by measuring the plasma levels of testosterone and dihydrotestosterone, SHBG binding capacity and salivary levels of testosterone. Plasma levels of testosterone, dihydrotestosterone and salivary testosterone levels were significantly lower in patients on haemodialysis than in controls. There was also a reduction in 5 alpha-reductase activity as evidenced by a reduced 5 alpha DHT/T ratio. SHBG levels were comparable to those found in eugonadal men. No differences were found in the parameters studied before and after 6 h haemodialysis. It is concluded that haemodialysis is not of obvious benefit to gonadal function.

The effect of progesterone administration on sex hormone binding globulin binding capacity in women with severe premenstrual syndrome

Thirty-one women with severe premenstrual syndrome had low sex hormone binding globulin (SHBG) binding capacities 30.2 ± 9.4 nmol DHT bound/1. The SHBG binding capacities rose when they were treated with three different doses of progesterone. On 400 mg (17 women) SHBG level was 45.11 ± 11.80. On 800 mg (8 women) SHBG binding capacity rose to 64.75 ± 14.30 and on the six women who took 1200 mg progesterone daily SHBG binding capacity was 78.5 ± 23.10. These results are discussed.

A versatile method for the determination of serum cortisol binding globulin and sex hormone binding globulin binding capacities

Cortisol binding globulin (CBG) and sex hormone binding globulin (SHBG) are plasma glycoproteins which bind some of the most important steroid hormones in blood with high affinity and specificity, but limited capacity. Although antisera have been raised against purified preparations of these proteins and radioimmunoassays have been developed to measure their actual serum concentrations [ 1,2], determinations of their steroid binding capacities will continue to be of importance, especially if variants with abnormal steroid binding activities exist [3,4]. In general, most methods currently used to determine the serum or plasma binding capacities of CBG and SHBG yield values which are in close agreement [5,6]. However, some of these methods are not suited for the routine analysis of large numbers of samples [7,8] while others require the use of expensive gels [9,10], or work under cold room conditions [ 111. Ammonium sulphate precipitation is probably the most widely used method to determine serum SHBG binding capacity [ 12141, but this technique is not so easily applied for measurement of CBG binding capacity, and cannot be readily adapted to measure SHBG binding capacity in samples containing low concentrations of protein, such as obtained during purification procedures. It has been our intention therefore to develop a reliable, inexpensive, versatile method that is suitable for the routine determination of both CBG and SHBG in dilute serum samples.

Clinical and laboratory predictors of clomiphene response

A prospective study was carried out on 158 anovulatory women for the purpose of finding parameters that might predict the clomiphene dose at which ovulation would occur. Both body weight and obesity were positively correlated with the dose required to ac;hieve ovulation (P < 0.05). Once ovulation occurred, obesity did not affect the ability to conceive. Fifty-eight women who ovulated with various doses of clomiphene, including six women who failed to ovulate, had hormonal measurements performed prior to treatment. Compared with normally ovulating controls, serum luteinizing hormone (LH), the ratio of LH to follicle-stimulating hormone (FSH), serum androgens, unbound testosterone, and unbound estradiol were elevated and sex hormone binding globulin-binding capacity (SHBG-BC) significantly lower in women receiving clomiphene. Although the ovulatory dose of clomiphene Was positively correlated with both weight and obesity, neither weight nor any laboratory parameter could accurately predict the clomiphene response.

Measurement of sex hormone binding globulin in human amniotic fluid: its relationship to protein and testosterone concentrations, and fetal sex.

Sex hormone binding globulin (SHBG) has been identified and quantified in human amniotic fluid. Identification was based on its electrophoretic mobility on polyacrylamide gels and its steroid binding characteristics, which were identical to those attributed to SHBG in pregnancy serum. Amniotic fluid SHBG binding capacity was measured by competitive saturation analysis using [3H]-5 alpha-dihydrotestosterone as the labelled ligand, after removal of endogenous steroids with dextran-coated charcoal. Similar amniotic fluid SHBG binding capacities were found in samples taken during early (13-20 weeks, 8.5 +/- 5.1 (SD) nmol/l, n = 10) and late (36-37 weeks, 8.7 +/- 3.0 nmol/l, n = 28) pregnancy. In comparison with pregnancy serum SHBG levels (390 +/- 140 nmol/l, n = 5), amniotic fluid SHBG was not enriched in relation to the relative concentrations of total proteins, albumin or transferrin. Amniotic fluid is therefore not a better source for the purification of SHBG than pregnancy serum. There were no differences in amniotic fluid SHBG levels with respect to fetal sex, but positive correlations were observed between SHBG binding capacities and testosterone concentrations in amniotic fluid from both male (r = 0.68, P less than 0.001) and female (r = 0.53, P less than 0.05) fetuses. It is suggested that SHBG may sequester free testosterone in amniotic fluid, and that measurements of SHBG in amniotic fluid may help to more accurately identify fetal sex in cases where borderline amniotic fluid testosterone concentrations are found.

Effects of a continuous estrogen-progestogen therapy for climacteric symptoms on circulating sex steroids and gonadotrophins.

Twenty-six peri- and postmenopausal women with climacteric symptoms were given each day for 1 year a tablet containing 2 mg 17-beta-estradiol, 1 mg estriol and 1 mg norethisterone acetate. Blood samples were collected before, after 3 months and after 12 months of treatment and were analysed for their gonadotrophins, estradiol, estrone, testosterone, androstenedione content and for their SHBG binding capacity. Serum levels of estrone and androstenedione before treatment were found to be higher in the perimenopausal than in the postmenopausal group. An increase of serum estrogens concomitant with a decrease of gonadotrophins was noted. The estrone/estradiol ratios after 3 and 12 months of treatment were 5.3 and 4.7, respectively. A decrease in the serum concentration of testosterone and androstenedione was recorded during treatment. The reduction of gonadotrophins, especially LH, might have been responsible for the reduction in circulating androgens. The reduction of serum levels of androgens during the present long-term replacement therapy could be of metabolic importance.

Normalization of androgen and sex hormone-binding globulin levels after treatment of hyperprolactinemia.

Twenty-eight women with amenorrhea, galactorrhea and hyperprolactinemia without hirsutism were studied before and after bromocriptine therapy for 2 months. Compared to 15 euprolactinemic controls, hyperprolactinemic women had elevated levels of dehydroepiandrosterone sulfate and androstenedione and lower levels of total testosterone (T), and androst-5-ene-3 beta, 17 beta-diol (Adiol), and 17 beta-estradiol (P less than 0.05). Unbound T and unbound Adiol were significantly elevated, while sex hormone-binding globulin binding capacity was decreased (P less than 0.05) and corticosteroid-binding globulin binding capacity was normal. After treatment with bromocriptine, dehydroepiandrosterone sulfate and androstenedione decreased to control levels, as did unbound Adiol, while 17 beta-estradiol and sex hormone-binding globulin binding capacity levels increased significantly (P less than 0.05). Five hyperprolactinemic women underwent ACTH stimulation tests before and after treatment, and the results were compared to those of seven controls. Steroid ratios in response to ACTH suggested normal 3 beta ol-dehydrogenase-isomerase, 17-20-desmolase and 17 beta-hydroxysteroid dehydrogenase enzymatic activities in hyperprolactinemia. Basal steroid ratios of T to 5 alpha-androstane-17 beta-01-3-one) (DHT) and of unbound T to unbound dihydrotestosterone were elevated (P less than 0.05), suggesting reduced 5 alpha-reductase activity in hyperprolactinemia which is normalized after treatment. Hirsutism was not present in these patients with hyperprolactinemia despite elevated levels of unbound T and Adiol, and may be explained by reduced 5 alpha-reductase activity. Our data suggest that the increased levels of androgens in these patients result from the hyperprolactinemia.

Clinical pharmacokinetics of oral contraceptive steroids.

Oral contraceptive steroids are of 2 types: oestrogens, of which ethinyloestradiol is the most important, and progestagens, of which levonorgestrel and norethisterone are the most commonly used. All these steroids can be measured by a number of analytical techniques but there is little doubt that radioimmunoassay is the most convenient. All the steroids are well absorbed in humans but while levonorgestrel is completely bioavailable, norethisterone has an average bioavailability of 70%. Ethinyloestradiol, too, is subject to presystemic metabolism with a mean bioavailability of 40 to 45%. The main site of presystemic metabolism is the gut wall, with the production of ethinyloestradiol sulphate. The progestagens norethynodrel, ethynodiol diacetate and lynoestrenol are quantitatively metabolised to norethisterone. The pharmacokinetics of the contraceptive steroids are best described by a 2-compartment open model. The terminal plasma half-life of levonorgestrel varies from 11 to 45 hours and of norethisterone from 5 to 14 hours. The β-phase half-life of ethinyloestradiol varies from 6 to 20 hours. The apparent volume of distribution of these contraceptive steroids (after intravenous administration) is between 1.5 and 4.3 L/kg. During long term treatment with oral contraceptive steroids, steady-state plasma concentrations of ethinyloestradiol (24 hours after administration) are between 10 and 200 pg/ml. Plasma concentrations of norethisterone and levonorgestrel at steady-state are higher than predicted from the single-dose kinetics because of enhanced binding of the progestagens following the induction of sex hormone binding globulin (SHBG) by ethinyloestradiol. Concentrations are in the range of 1.6 to 15.2 ng/ml for norethisterone and 0.8 to 4.5 ng/ml for levonorgestrel. All the contraceptive steroids are bound to proteins in plasma. Ethinyloestradiol is 97 to 98% bound to plasma albumin. The progestagens are bound both to albumin (levonorgestrel 93 to 95%; norethisterone 79 to 80%) and more specifically to SHBG. The binding capacity of SHBG can be enhanced by treatment with ethinyloestradiol or with more conventional enzyme-inducing drugs such as phenobarbitone, carbamazepine or rifampicin. Norethisterone and levonorgestrel are chiefly metabolised by reduction in the A ring and this is followed by conjugation with glucuronide or sulphate. The metabolism of levonorgestrel is stereoselective. Ethinyloestradiol is primarily hydroxylated at the 2 position but a wide variety of hydroxylated and methylated metabolites are formed and these are present both free and as glucuronide and sulphate conjugates. Ethinyloestradiol is conjugated directly at the 3 position (unlike the progestagens) and thus is liable to enterohepatic recirculation. Ethinyloestradiol sulphate concentrations in plasma are many times higher than that of the unchanged drug. The oral contraceptive steroids are involved in drug interactions of clinical significance. While the effect of contraceptive steroids on other drugs is small and unlikely to be of clinical significance, failure of contraception often occurs if enzyme-inducing agents such as rifampkin, phenobarbitone or carbamazepine are coadministered. Oral antibiotics do not seem to cause a significant loss of contraception in the large majority of women. Vitamin C will enhance the effect of contraceptive steroids by competing for sulphate conjugation in the gut wall, thus leading to increased bioavailability of ethinyloestradiol.

Changes in unbound sex steroids and sex hormone binding globulin-binding capacity during oral and vaginal progestogen administration

Four groups of five cycling women each received either a contraceptive vaginal ring containing a combination of either levonorgestrel or norethindrone with estradiol or oral contraceptives containing a combination of either dl-norgestrel or norethindrone with ethinyl estradiol. Pretreatment as well as 2- and 7-week treatment serum samples were assayed for sex hormone binding globulin-binding capacity (SHBG-BC), estradiol, non-SHBG-bound estradiol, testosterone, and non-SHBG-bound testosterone, d-norgestrel, non-SHBG-bound d-norgestrel, and norethindrone. SHBG-BC was significantly increased in the norethindrone oral contraceptive group, unchanged in the norgestrel oral contraceptive group, and significantly reduced in both contraceptive vaginal ring groups. These findings indicate that the positive effect of oral ethinyl estradiol on SHBG-BC offsets the suppressive effects of d-norgestrel on SHBG-BC, while the estradiol in the d-norgestrel or norethindrone contraceptive vaginal rings is insufficient to alter the suppressive effect of d-norgestrel or norethindrone on SHBG-BC. In contrast, the ethinyl estradiol in the norethindrone oral contraceptive overcame the suppressive effect of norethindrone on SHBG-BC, resulting in a significantly increased SHBG-BC level. Although total circulating estradiol was significantly decreased in the contraceptive vaginal ring groups, the percentage of unbound serum estradiol was significantly increased in both contraceptive vaginal ring groups and significantly reduced in the norethindrone oral contraceptive group. Although total circulating testosterone was significantly reduced only in the norgestrel oral contraceptive group, the percentage and mass of unbound testosterone were significantly decreased in the norethindrone oral contraceptive group, while the percentage of unbound testosterone was significantly reduced in the norgestrel oral contraceptive group and significantly increased in the norethindrone contraceptive vaginal ring group. As levels of unbound (biologically active) steroid differ markedly from levels of total steroid, it is essential to measure levels of non-SHBG-bound estradiol and testosterone in order to detemine effects of steroidal contraceptives on physiologically active circulating endogenous steroids.

Comparison of pharmacodynamic properties of various estrogen formulations

A group of 23 healthy postmenopausal women received one or more 2-week courses of daily administration of the following estrogen preparations: piperazine estrone sulfate (Ogen), 0.3, 0.625, 1.25, 2.5, and 5.0 mg; micronized estradiol (Estrace), 1,2, and 10 mg; conjugated estrogens (Premarin), 0.3, 0.625, 1.25, and 2.5 mg; ethinyl estradiol (Estinyl), 10 and 20 μg; and diethylstilbestrol, 0.1 and 0.5 mg. Each dosage of each formulation was ingested by three women. In those women who received more than one dosage, each course was separated by a drug-free interval of at least 4 weeks. Pretreatment and posttreatment levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), corticosteroid-binding globulin-binding capacity, sex hormone-binding globulin-binding capacity, angiotensinogen, estrone, and estradiol were determined. The relative potency of these five estrogen formulations was determined by parallel line analysis for each of these responses, except LH. On a weight basis, piperazine estrone sulfate and micronized estradiol were equipotent for all responses. Conjugated estrogens suppressed FSH in a fashion equipotent to that of the other nonsynthetic estrogens; however, for all three hepatic parameters, the response was exaggerated twofold to threefold. The synthetic estrogens, diethylstibestrol and ethinyl estradiol, were relatively more potent on a weight basis for every response and produced the most marked response (fourfold to eighteenfold in excess of their FSH suppression) for the hepatic parameters.

Distribution and percentages of non-protein bound contraceptive steroids in human serum

The percentages of non-protein bound ethinyl-estradiol (EE 2), norethisterone (NET), d-norgestrel and cyproterone-acetate (CA) have been measured by centrifugal ultrafiltration-dialysis in undiluted serum at 37°C. The respective percentages (mean ± SD) of these steroids which are non-protein bound in serum from normal men ( n = 5) and women ( n = 10) are as follows: EE 2, 1.44 ± 0.15, and 1.54 ± 0.16; NET, 4.71 ± 0.55 and 3.69 ± 0.90; d-norgestrel, 3.05 ± 0.34 and 2.50 ± 0.68; CA, 6.62 ± 0.43 and 7.22 ± 0.96. Similar values were found for samples taken during follicular and luteal phases of the menstrual cycle. Percentages of non-protein bound serum EE 2 and CA were similar in both sexes, while those for NET ( P < 0.05) and d-norgestrel ( P < 0.2) appear to be higher in serum from men than women. Furthermore, the percentages of non-protein bound EE 2 (1.58 ± 0.14, n = 4) and CA (6.33 ± 1.01, n = 5) in third trimester pregnancy sera were similar to those in serum samples from men and non-pregnant women, while those of NET (1.06 ± 0.21, n = 5) and d-norgestrel (1.19 ± 0.29, n = 4) were much lower ( P < 0.001) in pregnancy serum than in any of the other samples. These differences are probably a consequence of NET and d-norgestrel binding to sex-hormone binding globulin (SHBG), since correlations were observed between serum SHBG binding capacities and percentages of non-protein bound NET and d-norgestrel, and because heat denaturation of SHBG binding capacity by >90% almost completely abolished these differences. By comparing the non-protein bound percentages of steroids in native and heat treated (60° for 1 h) serum, it was calculated that in native serum both EE 2 and CA are almost exclusively bound by the heat stable component (predominantly albumin), which binds >98.5% of EE 2 and >93.0% of CA in both men and women. In contrast, the respective percentages of NET and d-norgestrel bound to SHBG are 20.57 ± 11.38 and 37.73 ± 7.66 in men, and 35.49 ± 13.64 and 47.54 ± 11.69 in women, while the percentages of these steroids bound to albumin are 74.72 ± 10.94 and 59.21 ± 7.33 in men, and 60.82 ± 12.94 and 49.96 ± 11.05 in women, respectively. These data indicate that the distributions of NET and d-norgestrel between various serum binding proteins are determined largely by SHBG binding capacity, and that knowledge of the latter may be useful in assessments of the lowest effective dose of these two progestins in different individuals.