Divergent effects of two low-dose oral contraceptives on sex hormone-binding globulin and free testosterone

The effect of a triphasic combination of ethinyl estradiol and levonorgestrel on the serum concentrations of total testosterone, free testosterone, and sex hormone-binding globulin as measured directly by radioimmunoassay and on the binding capacity of sex hormone-binding globulin was compared with that of a preparation containing ethinyl estradiol and desogestrel. Blood samples were taken on days 6, 11, 21, and 28 of a control cycle, the third cycle of treatment with either ethinyl estradiol-levonorgestrel or ethinyl estradiol-desogestrel (11 volunteers each), the third cycle of a 3-month washout period, and the third treatment cycle after crossover change of the preparations. There was a significant reduction in total testosterone by 16% during treatment with both preparations. Ethinyl estradiol-desogestrel increased the concentration (+175%) and binding capacity (+330%) of sex hormone-binding globulin to a much greater extent than with ethinyl estradiol-levonorgestrel (+92% and +160%). Contrary to this, a significant suppression of non-protein-bound testosterone by 35% was found during treatment with both oral contraceptives. The results demonstrate that an excessive elevation of the levels of sex hormone-binding globulin above the normal range does not cause a corresponding suppression of free testosterone. It is assumed that the decrease in the apparent binding affinity of high sex hormone-binding globulin concentrations to testosterone may be due to protein-protein interactions.     

Effects of hormone therapy and alendronate on C-reactive protein,E-selectin,and sex hormone-binding globulin in osteoporotic women

OBJECTIVE: C-reactive protein and soluble E-selectin hold promise as surrogate markers for future cardiovascular events. We studied the effects of oral hormone therapy (HT) and alendronate, given alone or together, on these markers and on sex hormone-binding globulin levels in osteoporotic elderly women. DESIGN: Prospective, randomized, double-dummy trial. SETTING: Outpatient department of a university hospital. PARTICIPANT(S): Ninety osteoporotic women (T score < or =2.5 at the lumbar spine or femoral neck) 65 to 80 years of age. INTERVENTION(S): Randomized assignment to 1 year of treatment with estradiol, 2 mg p.o., plus norethisterone acetate, 1 mg (hormone therapy); alendronate, 10 mg; or HT plus alendronate. MAIN OUTCOME MEASURE(S): Serum levels of C-reactive protein, E-selectin, and sex hormone-binding globulin were measured at baseline, 6 months, and 12 months. RESULT(S): Hormone therapy significantly increased C-reactive protein levels by 76.5% at 6 months and by 47.1% at 12 months, but reduced E-selectin levels by 24.3% at 6 months and by 30.0% at 12 months. Alendronate had no effect on C-reactive protein or E-selectin and failed to modify the responses of C-reactive protein or E-selectin to hormone therapy. Hormone therapy increased sex hormone-binding globulin levels, whereas alendronate had no effect on this substance. CONCLUSION(S): The increase in C-reactive protein level in response to oral HT in elderly osteoporotic women may result from stimulated synthesis of C-reactive protein in the liver, whereas the decrease in E-selectin level may reflect a direct effect of HT on endothelial cells. Alendronate has no effect on vascular markers or sex hormone-binding globulin.     

Second-trimester sex hormone-binding globulin and subsequent development of pre-eclampsia.

OBJECTIVE: To investigate whether maternal plasma sex hormone-binding globulin (SHBG) concentrations are reduced in women who subsequently develop pre-eclampsia. METHODS: This was a cross-sectional study, carried out at antenatal clinics in seven hospitals in and around London. Healthy women underwent uterine artery Doppler velocimetry as a screening method for pre-eclampsia at 22-24 weeks of gestation. The first group (408 women) had normal uterine artery Doppler waveforms (mean uterine artery pulsatility index (PI) below 1.6). The second group (274 women) had increased impedance to flow in the uterine arteries (mean PI above the 95th centile, 1.6). Maternal plasma SHBG concentrations were measured retrospectively using a competitive chemiluminescent immunoassay. Pre-eclampsia was as defined by the International Society for the Study of Hypertension in Pregnancy. RESULTS: Plasma SHBG concentrations in the 80 (11.7%) women who subsequently developed pre-eclampsia were significantly lower than in the 585 (85.8%) women with normal pregnancy outcomes (median 336, range 142-674 nmol/l vs. median 336, range 142-674 nmol/l, p = 0.001). There was a strong correlation between SHBG concentrations and body mass index (r =-0.232246, p < 0.0001). There were no significant differences in maternal plasma SHBG concentrations in women with abnormal uterine artery Doppler (n = 274) compared with controls (n = 408) (median 324, range 101-635 nmol/l vs. median 336, range 142-674 nmol/l, p = 0.09). CONCLUSION: Maternal plasma SHBG concentrations are reduced in women who subsequently develop pre-eclampsia.     

Pharmacokinetics of synthetic sex steroids in hormonal contraceptives

The pharmacokinetics of synthetic contraceptive steroids are dependent on several factors: e.g. body weight, ethnic factors, dosage of steroids, particle size, absorption, metabolism, elimination, affinity to proteins (SHBG, albumine), interaction etc. The dosage-dependent changes of pharmacokinetics progestagens and estrogens are presented. Besides, the principle of interactions between estrogens and progestagens and other drugs is discussed. Pharmacokinetic studies of oral contraceptive steroids should be designed according to the recommended modus of application. The analysis of the involved steroids, estrogen and progestagen, and of the combined pill should be carried out with regard to age, season and duration of application.     

Changes in serum sex hormone-binding globulin, free estradiol, and testosterone during gonadotropin treatment

Sex hormone-binding globulin (SHBG), estradiol (E2), percent free E2, percent of E2 bound to SHBG, and testosterone (T) were evaluated in 28 ovulatory women during human menopausal gonadotropin-stimulated cycles for in vitro fertilization. Patients were divided into two categories: low responders, in whom serum E2 concentration reached levels less than 1000 pg/ml (mean, 638 +/- 93), and high responders, with serum E2 levels greater than 1000 pg/ml (mean, 2219 +/- 330). A significant increase in SHBG can occur within a short time in high responders (from 62.8 to 103.9 nmol/l) but not in low responders. This increase is accompanied by a significant decrease in the percent free (bioavailable) E2, but the distribution of E2 between the fraction bound to SHBG or albumin did not vary. Despite the increase in the levels of SHBG, the concentration of bioavailable (free) E2 in hyperstimulated women is higher than in normal cycles. The significant increase in T in high responders, by virtue of its higher affinity for SHBG, probably contributes to the increased levels of bioavailable E2.     

Plasma androgens and sex hormone-binding globulin in the evaluation of hirsute females

Hirsutism is usually associated with increased testosterone (T) production and metabolic clearance rates. Considerable overlap of plasma T occurs between hirsute and normal groups. Plasma levels of sex hormone-binding globulin (SHBG) and the factor T/SHBG might separate hirsute patients from normal subjects better than plasma T. A group of 39 hirsute females and 22 normal ovulatory control subjects were studied. Plasma T, androstenedione, and dehydroepiandrosterone were measured by radioimmunoassay; apparent free T (AFT) by equilibrium dialysis; and SHGBG by a method based on saturating the binding sites by labeled dihydrotestosterone. Mean levels of androgens and SHBG of the hirsute patients were significantly different from those of the normal subjects (P less than 0.01). Positive linear correlations were observed between T and AFT, T/SHBG and AFT, and T/SHBG and T; a negative correlation was observed between T/SHBG and SHBG, but no correlation was observed between SHBG and T or AFT. Thirty (77%) of the patients had elevated T/SHBG factors and 28 (72%) had suppressed SHBG levels. Only two patients (5%) had hirsutism associated with normal levels of androgens, SHBG, and T/SHBG. We conclude that SHBG and the factor T/SHBG separate the hirsute population better than any of the androgens studied.     

Opioid regulation of pituitary gonadotropins and prolactin in women using oral contraceptives

To determine the effect of oral contraceptives on endogenous opioid modulation of the hypothalamic-pituitary axis, we gave a bolus dose of 10 mg of naloxone intravenously in women using Lo/Ovral-28 oral contraceptives and in normal (control) women during the follicular (days 8 to 9) and luteal (days 21 to 23) phases. Plasma follicle-stimulating hormone, luteinizing hormone, and prolactin were measured by radioimmunoassay before and after naloxone at regular intervals. In oral contraceptive users (n = 5) basal plasma follicle-stimulating hormone (3.7 +/- 0.4 mIU/ml) and luteinizing hormone (3.2 +/- 0.5 mIU/ml) levels were significantly lower than in control subjects during both follicular (10.7 +/- 0.9 and 16.7 +/- 2.0) and luteal (7.7 +/- 1.4 and 10.0 +/- 0.9, respectively) phases (p less than 0.05 to 0.001). In contrast the basal plasma prolactin level was significantly higher in oral contraceptive users (25.0 +/- 4.1 ng/ml) than in control subjects during the follicular (11.8 +/- 1.2) and luteal (11.0 +/- 0.8) phases (p less than 0.01). In control subjects, follicle-stimulating hormone, luteinizing hormone, and prolactin levels did not change significantly after naloxone in the follicular phase, but naloxone elicited a significant synchronous release of luteinizing hormone and prolactin during the luteal phase. In contrast, oral contraceptive users showed increases in luteinizing hormone and prolactin after naloxone that were not significantly different from the basal plasma levels.     

Serum and follicular fluid sex hormone-binding globulin in stimulated and unstimulated cycles

Background It is wellknown that sex hormone-binding globulin (SHBG) concentrations in the follicle are relatively low in comparison with the corresponding estradiol (E₂) levels, which are extremely high. A direct comparison of these data in stimulated and unstimulated cycles, as well as the relationship of SHBG with testosterone (T) and E₂ in serum and follicular 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 corresponding total estradiol and total testosterone concentrations. The analyzed FFs of 42 women, 12 of whom conceived, were randomly selected 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 contrast, serum T and E₂ were significantly higher in induced than in unstimulated cycles, while there was no significant difference in FF T or E₂ between the two groups of cycles. No correlation was found between serum and FF SHBG in either stimulated or unstimulated cycles. In stimulated cycles, only in FF, SHBG was significantly correlated with both E₂ and T. In unstimulated cycles, no correlation was found between SHBG and either one of the corresponding steroids either in serum 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.Presented in part at the VIIIth World Congress on in Vitro Fertilization and Alternate Assisted Reproduction, Kyoto, Japan, 1993.     

The relationship of insulin to sex hormone-binding globulin: role of adiposity

The role of adiposity in the relationship of insulin to sex hormone-binding globulin (SHBG) concentration was examined in 31 healthy premenopausal women of varying body weight. Fat mass was estimated by hydrostatic weighing. Concentrations of SHBG and testosterone (T) and cumulative insulin response during an oral glucose tolerance test were measured. The cumulative insulin response was inversely related to SHBG (r = -0.56, P less than 0.01). The relationship between SHBG and cumulative insulin response remained significant (r = -0.47, P less than 0.01) after adjusting for fat mass and T. The fat mass correlated significantly with SHBG (r = -0.51, P less than 0.01). The relationship of SHBG to fat mass remained significant after adjusting for T (r = -0.45, P less than 0.01). However, the relationship between fat mass and SHBG was no longer significant (r = -0.34, P greater than 0.05) after adjusting for cumulative insulin response. Hyperinsulinemia may play an important role in the progressive reduction of SHBG observed with increasing adiposity.     

Expression of sex hormone-binding globulin, oxytocin receptor, caveolin-1 and p21 in leiomyoma.

BACKGROUND: Interaction of sex hormone-binding globulin (SHBG) and oxytocin (OT) is among the factors that control smooth muscle proliferation and tumor growth through the oxytocin receptor (OTR). Also, a close functional interaction of OTR and caveolin-1 has been shown to modulate cell growth and proliferation. METHODS: We studied surgical samples from 23 leiomyoma patients (aged 33-66 years) with immunocytochemistry. Specimens from five patients (34-76 years), who had hysterectomy for other reasons, served as controls. Tissue samples were cut into serial 1-microm thick sections for co-localization of SHBG, OTR, proliferation marker p21 and caveolin-1. RESULTS: SHBG was found in smooth muscle cells in all samples. OTR staining occurred in most of these cells in myomas, while controls contained only scattered cells positive for OTR. There were no apparent differences in immunostaining for p21, while immunoreactivity for caveolin-1 was observed in most cells in myomas and in only few cells in controls. Caveolin-1 was mostly co-localized with SHBG and OTR in myoma samples whereas controls showed this co-localization only occasionally. CONCLUSIONS: Our observations indicate an interaction of SHBG and OTR, associated with caveolin-1, which may account in part for known non-genomic actions of ovarian steroids. Growth of leiomyomas may be linked to these mechanisms.     

Effect of low-dose oral contraceptive on gonadotropins, androgens, and sex hormone binding globulin in nonhirsute women

The effectiveness of a low-dose oral contraceptive (OC) in suppressing plasma levels of gonadotropins, ovarian, and adrenal androgens and stimulating sex hormone-binding globulin (SHBG) was evaluated prospectively in nonhirsute women. Thirty-three women ingested 35 micrograms of ethinyl estradiol and 1 mg of norethindrone beginning within day 1 to 5 of the menstrual cycle. Baseline levels of luteinizing hormone, follicle-stimulating hormone, total testosterone (T), androstenedione (A), dehydroepiandrosterone sulfate (DHEAS), and SHBG were obtained before ingestion of the OC and repeated after 3, 6 and, 9 months of OC use on day 1 to 5 of the OC "cycle". A significant suppression of gonadotropin levels is seen in nonhirsute women. Sex hormone binding globulin is consistently stimulated by the low-dose OC. A significant suppression of T and DHEAS is observed. No change was seen in levels of A. The demonstrated effects become evident at 3 months and are maintained at 6 and 9 months.     

Decreasing serum levels of sex hormone-binding globulin around the menopause and temporary relation to changing levels of ovarian steroids, as demonstrated in a longitudinal study

Blood samples collected longitudinally in 17 women over a period of 3 years, starting 11/2 years before the menopause, were assessed for sex hormone-binding globulin (SHBG), 17 beta-estradiol (E2), progesterone, and total testosterone. A slight (7.2%) decrease in mean SHBG from 4.25 +/- 1.67 (standard deviation) mg/l to 3.95 +/- 1.61 mg/l was observed within the 6-month period encompassing the menopause. More specifically, the decrease appeared to commence at the menopause and to become clearly significant (P = 0.01) some 2 to 6 months later. During the subsequent year, a further decrease to 3.64 +/- 1.42 mg/l was observed, amounting to a total decrease in mean SHBG by 14.4% (P less than 0.001). Of the hormones, only E2 exhibited a marked decrease (P less than 0.01) within this same 6-month period. The changes in SHBG during the 6-month transition period from premenopause to postmenopause correlated significantly (P = 0.013) only with those of E2. It is concluded that decreasing E2 levels appear to play a significant role in the downward modulation of SHBG levels commencing at the menopause.     

Serum pharmacokinetics of orally administered desogestrel and binding of contraceptive progestogens to sex hormone-binding globulin

Serum levels of 3-ketodesogestrel and ethinyl estradiol were analyzed by radioimmunoassay in a balanced crossover study with two tablet formulations containing desogestrel (0.150 mg) and ethinyl estradiol (0.030 mg) in 25 women under steady-state conditions after 21 days of treatment. The pharmacokinetic properties of desogestrel were characterized by the following parameters: (1) maximum serum concentration, (2) time to maximum serum concentration, (3) total area under the serum concentration versus time curve, and (4) serum half-life of elimination. The interindividual variation in these parameters was comparable with that observed with other contraceptive combinations containing ethinyl estradiol and norethisterone, levonorgestrel, or gestodene. The serum distribution of contraceptive progestogens is known to be determined by their affinity to sex hormone-binding globulin and the concentration of sex hormone-binding globulin. We analyzed the structural features that determine binding to sex hormone-binding globulin. The 18-methyl group increased and the 11-methylene group weakened the binding to sex hormone-binding globulin. The double bond at C-15 reinforced the binding only when combined with an 18-methyl group. Therefore, the binding of levonorgestrel (the 18-methyl derivative of norethisterone) and gestodene (the Δ-15,18 methyl derivative of norethisterone) to sex hormone-binding globulin was much stronger than that of 3-keto-desogestrel and norethisterone.     

Reference intervals for serum sex steroids and gonadotropins in regularly menstruating women.

Reference intervals for novel fluoro-immunoassays for serum luteinizing hormone (LH), follicle stimulating hormone (FSH), estradiol (E2) and progesterone (P) were established in 40 healthy regularly menstruating women. Serum samples for sex steroids, including testosterone (T), androstenedione (A) and dehydroepiandrosterone sulphate (DHEAS), as well as sex hormone binding globulin (SHBG) and gonadotropins, were collected in the early follicular and mid-luteal phases of the menstrual cycle. The need for the timing of androgen and gonadotropin samples was also determinated. Serum E2 and P were measured by radio-immuno- and time-resolved fluoro-immunoassays. Various assay methods correlated closely, but the reference intervals varied considerably from one method to another. In the early follicular phase the LH/FSH ratio only ranged between 0.2 and 1.7 (mean +/- S.D.; 0.8 +/- 0.3); the variation was greater (from 0.3 to 3.5) in the luteal phase, when the mean was also significantly higher (1.5 +/- 0.9, p = 0.0001). Similarly the mean values of T and SHBG were higher in the luteal phase, while the other androgen concentrations and calculated androgen indexes were equal, compared with the follicular phase values. Thus the timing of hormone determinations is warranted in the investigation of the gonadotropin and androgen status in normally menstruating women. Moreover, the upper limit of the LH/FSH ratio examined with new, sensitive methods is lower than that previously stated. The use of an intra-uterine contraceptive device (IUD) had no effect on hormone levels.