A liquid-phase immunoradiometric assay (IRMA) for human sex hormone binding globulin (SHBG)

Effects of androgenic properties of progestin combined with ethinyl estradiol on vascular endothelial reactivity, plasma lipids and free radical production in women with endometriosis

AIM

Endothelial reactivity is inhibited and oxidative stress is enhanced in women with endometriosis. Testosterone may adversely affect lipids and endothelium. We investigated the effects of androgenic properties of progestins combined with ethinyl estradiol (EE) on endothelial function, lipids and free radical production in such women.

METHODS

Women with endometriosis were treated with 20 μg EE + 3 mg drospirenone (DRSP) or 35 μg EE + 1 mg norethisterone (NET) for 3 months. Plasma concentrations of sex hormone-binding globulin (SHBG), lipids, copper (Cu), derivatives of reactive oxygen metabolites (d-ROMs), biological antioxidant potential (BAP), nitrite/nitrate, endothelin-1 and asymmetrical dimethylarginine (ADMA) were measured before and after treatment. Flow-mediated vasodilation (FMD) of the brachial artery was measured by ultrasonography.

RESULTS

DRSP group, but not NET group, significantly increased FMD and concentrations of nitrite/nitrate and small dense LDL cholesterol, while decreased endothelin-1 concentrations. In both groups, ADMA and LDL cholesterol concentrations were significantly decreased, but triglyceride, SHBG, d-ROMs, Cu and ceruloplasmin concentrations increased, and BAP concentrations did not change. DRSP group significantly increased HDL cholesterol concentrations, whereas NET group decreased its concentrations. Changes in triglyceride correlated positively either with changes in SHBG (r = 0.57, P < 0.001) or with small dense LDL cholesterol (r = 0.45, P = 0.005). Changes in Cu correlated positively with changes in d-ROMs (r = 0.87, P < 0.001).

CONCLUSION

Androgenic properties of progestin may counteract EE's favorable effects on endothelial function and HDL cholesterol, while eliminating its adverse effects on increased triglyceride-induced small dense LDL cholesterol in women with endometriosis.

Hepatic Effects of Estrogen on Plasma Distribution of Small Dense Low-Density Lipoprotein and Free Radical Production in Postmenopausal Women

AIM

Hepatic effects of estrogen therapy on low-density lipoprotein (LDL) subfraction or oxidative stress have not been previously evaluated. The purpose of the present study was to investigate whether the differential hepatic effects of estrogen affect plasma distribution of small dense LDL and free radical production in postmenopausal women.

METHODS

In all, 45 postmenopausal women were given 0.625 mg/day of oral conjugated equine estrogen (CEE) (n=15), 1.0 mg/day of oral 17β estradiol (E2) (n=15), or 50 μg/day of transdermal 17βE2 (n=15) for 3 months. Subjects received either estrogen alone or with dydrogesterone at 5 mg/day. Plasma concentrations of sex hormone-binding globulin (SHBG), lipids, metallic ions, and derivatives of reactive oxygen metabolites (d-ROMs) were measured.

RESULTS

CEE, but not oral 17βE2, increased the plasma concentrations of triglyceride, copper (Cu), and d-ROMs and the ratio of small dense LDL/total LDL cholesterol, a marker for plasma distribution of small dense LDL. Transdermal 17βE2 decreased d-ROMs concentrations but did not significantly change other parameters. Plasma concentrations of SHBG increased in the 3 groups. Estrogen-induced changes in triglyceride correlated positively either with changes in SHBG (R=0.52, P=0.0002) or the ratio of small dense LDL/total LDL cholesterol (R=0.65, P＜0.0001). Changes in Cu also correlated positively either with changes in SHBG (R=0.85, P＜0.0001) or d-ROMs (R=0.86, P＜0.0001).

CONCLUSION

The hepatic effects of different routes or types of estrogen therapy may be associated with plasma distribution of small dense LDL and free radical production in postmenopausal women.

What maintains the high intra-follicular estradiol concentration in pre-ovulatory follicles?

PURPOSE

The purpose of the study was to establish the mechanism by which the estrogen concentration difference between the follicular fluid and the serum is maintained.

METHODS

We used dialysis membrane with a pore size of <3 KD to characterize the estrogen-binding capacity of the follicular fluid. We performed PCR, western blot, and ELISA on luteinized granulosa cells to determine if sex hormone-binding globulin (SHBG) is produced by granulosa cells, and finally we used affinity columns and mass spectrometry to identify the estrogen-binding protein in the follicular fluid.

RESULTS

We found that a significant estrogen concentration difference is maintained in a cell-free system and is lost with proteolysis of the follicular fluid proteins. Luteinized granulosa cells are likely not a source of SHBG, as we were not able to detect expression of SHBG in these cells. Perlecan was the most highly enriched follicular fluid protein in the affinity columns.

CONCLUSIONS

We were able to identify perlecan as the most likely candidate for the major estrogen-binding protein in the follicular fluid.

Naturally occurring mutants inform SHBG structure and function

SHBG transports and regulates the activities of androgens and estrogens. Several single nucleotide polymorphisms in the human SHBG gene have been linked to sex steroid-dependent diseases, including those associated with the metabolic syndrome. The N-terminal laminin G-like domain of SHBG includes binding sites for calcium, sex steroids, and fibulin family members, as well as a dimerization domain. We have found that 8 of 18 uncharacterized nonsynonymous single nucleotide polymorphisms within this domain alter the production or biochemical properties of SHBG in ways not previously recognized. O-Linked glycosylation at Thr7 is disrupted in SHBG T7N, whereas abnormal glycosylation of SHBG G195E limits its secretion. Three SHBG mutants (R135C, L165M, and E176K) bind estradiol with abnormally high affinity. SHBG R135C also has an increased interaction with fibulin-2. Two different substitutions within the dimer interface at R123 (R123H and R123C) reduce the affinity for 5α-dihydrotestosterone, while increasing the relative binding affinity for estradiol. SHBG T48I is defective in calcium binding, which leads to a defect in dimerization, reduced affinity for sex steroids, and an enhanced interaction with fibulin-2, which can all be restored by calcium supplementation. These naturally occurring mutants provide insight into SHBG structure and function, and defects in SHBG production or function need to be considered in the context of its utility as a biomarker of diseases.

Sexuality and androgens in women with cyclical mood changes and pre-menstrual syndrome

OBJECTIVE

To study the relation between androgen levels and sexual interest in women with different kinds of pre-menstrual syndrome (PMS).

DESIGN

Causal comparative study.

SETTING

Swedish university hospital outpatient clinic.

POPULATION

Seventy women with cyclical mood changes.

METHODS

Pre-menstrual syndrome patients were divided into those with and those without preovulatory symptoms. In 37 women, early follicular phase blood samples were analyzed for androstenedione, testosterone, sex hormone-binding globulin (SHBG), progesterone and estradiol, using radioimmunoassay. The participants were divided into subgroups depending on whether the levels of androgens and SHBG were above or below the median. In 33 of them it was possible to compare the cyclicity in sexual parameters between these subgroups.

MAIN OUTCOME MEASURES

Daily ratings of sexual parameters and hormonal analyses.

RESULTS

Plasma testosterone was significantly lower and SHBG significantly higher in women with luteal phase symptoms compared with those with additional follicular phase symptoms. ANOVA showed significant cyclicity for all sexual parameters consistently. For the "sexual feelings" and "pleasant sexual thoughts" parameters, cyclicity was the same whether or not the hormonal levels were "high" or "low."

CONCLUSIONS

The "Pure-PMS" group and the "pre-menstrual-exacerbation" groups differed in their androgen and SHBG levels. Women suffering from PMS with higher neuroticism Eysenck Personality Inventory scores or "low" levels of androgens and SHBG would be more likely to have a decreased sexual interest pre-menstrually than would women with a high level.

Selective cleavage of human sex hormone-binding globulin by kallikrein-related peptidases and effects on androgen action in LNCaP prostate cancer cells

Stimulation of the androgen receptor via bioavailable androgens, including testosterone and testosterone metabolites, is a key driver of prostate development and the early stages of prostate cancer. Androgens are hydrophobic and as such require carrier proteins, including sex hormone-binding globulin (SHBG), to enable efficient distribution from sites of biosynthesis to target tissues. The similarly hydrophobic corticosteroids also require a carrier protein whose affinity for steroid is modulated by proteolysis. However, proteolytic mechanisms regulating the SHBG/androgen complex have not been reported. Here, we show that the cancer-associated serine proteases, kallikrein-related peptidase (KLK)4 and KLK14, bind strongly to SHBG in glutathione S-transferase interaction analyses. Further, we demonstrate that active KLK4 and KLK14 cleave human SHBG at unique sites and in an androgen-dependent manner. KLK4 separated androgen-free SHBG into its two laminin G-like (LG) domains that were subsequently proteolytically stable even after prolonged digestion, whereas a catalytically equivalent amount of KLK14 reduced SHBG to small peptide fragments over the same period. Conversely, proteolysis of 5α-dihydrotestosterone (DHT)-bound SHBG was similar for both KLKs and left the steroid binding LG4 domain intact. Characterization of this proteolysis fragment by [(3)H]-labeled DHT binding assays revealed that it retained identical affinity for androgen compared with full-length SHBG (dissociation constant = 1.92 nM). Consistent with this, both full-length SHBG and SHBG-LG4 significantly increased DHT-mediated transcriptional activity of the androgen receptor compared with DHT delivered without carrier protein. Collectively, these data provide the first evidence that SHBG is a target for proteolysis and demonstrate that a stable fragment derived from proteolysis of steroid-bound SHBG retains binding function in vitro.

Cytoplasmic accumulation of incompletely glycosylated SHBG enhances androgen action in proximal tubule epithelial cells

Human sex hormone-binding globulin (SHBG) accumulates within the cytoplasm of epithelial cells lining the proximal convoluted tubules of mice expressing human SHBG transgenes. The main ligands of SHBG, testosterone and its metabolite, 5α-dihydrotestosterone (DHT), alter expression of androgen-responsive genes in the kidney. To determine how intracellular SHBG might influence androgen action, we used a mouse proximal convoluted tubule (PCT) cell line with characteristics of S1/S2 epithelial cells in which human SHBG accumulates. Western blotting revealed that SHBG extracted from PCT cells expressing a human SHBG cDNA (PCT-SHBG) is 5-8 kDa smaller than the SHBG secreted by these cells, due to incomplete N-glycosylation and absence of O-linked oligosaccharides. PCT-SHBG cells sequester [(3)H]DHT more effectively from culture medium than parental PCT cells, and the presence of SHBG accentuates androgen-dependent activation of a luciferase reporter gene, as well as the endogenous kidney androgen-regulated protein (Kap) gene. After androgen withdrawal, androgen-induced Kap mRNA levels in PCT-SHBG cells are maintained for more than 2 wk vs 2 d in parental PCT cells. Transcriptome profiling after testosterone or DHT pretreatments, followed by 3 d of steroid withdrawal, also demonstrated that intracellular SHBG enhances androgen-dependent stimulation (e.g. Adh7, Vcam1, Areg, Tnfaip2) or repression (e.g. Cldn2 and Osr2) of many other genes in PCT cells. In addition, nuclear localization of the androgen receptor is enhanced and retained longer after steroid withdrawal in PCT cells containing functional SHBG. Thus, intracellular SHBG accentuates the uptake of androgens and sustains androgens access to the androgen receptor, especially under conditions of limited androgen supply.

Immunoassay for sex hormone-binding globulin in undiluted serum is influenced by high-molecular-mass aggregates

BACKGROUND

The new Elecsys chemiluminescence assay for measurement of homodimeric sex hormone-binding globulin (SHBG) was designed for use with undiluted serum, in contrast to other methods that require predilution. During assay development, unexpected calibration difficulties were observed that were attributable to particular biochemical properties of the highly concentrated SHBG in solution.

METHODS

We used a surface plasmon resonance (SPR) biosensor, which enables biomolecular interaction analysis of SHBG, and size-exclusion chromatography for this investigation. The immunoassay was evaluated for imprecision, linearity, and suitability of the dilution medium, and the method was compared with an IRMA for SHBG.

RESULTS

The SPR biosensor characterized the special protein properties of SHBG in various concentrations. Above 200 nmol/L there was a strong tendency toward formation of high-molecular-mass aggregates. This was also detectable by size-exclusion chromatography and could be reversed by simple dilution of the sample. On the basis of these results, the dynamic measuring range of the SHBG assay is restricted to 0.350-200 nmol/L. Assay evaluation on a 2010 analyzer revealed excellent precision (CV <or=2.5%). Mean recoveries were 84.2-98.8%. Intermethod comparison with an IRMA yielded a satisfactory concordance of the two assays with a Spearman correlation coefficient of 0.8807.

CONCLUSIONS

Aggregates of human SHBG may have a detrimental impact on the accurate measurement of the protein if measurements are performed with undiluted serum samples. Further work is needed to clarify whether these high-molecular-mass aggregates influence the free fraction of steroid hormones in vivo.

Access of reproductive steroids to target tissues

The access of reproductive steroids to their target cells varies considerably between tissues, and is influenced to a great extent by their interactions with plasma steroid-binding proteins, and with SHBG and CBG in particular. An increased awareness of how SHBG and CBG function within the blood circulation, and within extravascular compartments of steroid-responsive target tissues, needs to be incorporated into the design and evaluation of therapies involving the administration of both natural and synthetic steroids, which influence female reproduction and healthy aging.

Steroid ligands bind human sex hormone-binding globulin in specific orientations and produce distinct changes in protein conformation

The amino-terminal laminin G-like domain of human sex hormone-binding globulin (SHBG) contains a single high affinity steroid-binding site. Crystal structures of this domain in complex with several different steroid ligands have revealed that estradiol occupies the SHBG steroid-binding site in an opposite orientation when compared with 5 alpha-dihydrotestosterone or C19 androgen metabolites (5 alpha-androstan-3 beta,17 beta-diol and 5 alpha-androstan-3 beta,17 alpha-diol) or the synthetic progestin levonorgestrel. Substitution of specific residues within the SHBG steroid-binding site confirmed that Ser(42) plays a key role in determining high affinity interactions by hydrogen bonding to functional groups at C3 of the androstanediols and levonorgestrel and the hydroxyl at C17 of estradiol. Among residues participating in the hydrogen bond network with hydroxy groups at C17 of C19 steroids or C3 of estradiol, Asp(65) appears to be the most important. The different binding mode of estradiol is associated with a difference in the position/orientation of residues (Leu(131) and Lys(134)) in the loop segment (Leu(131)-His(136)) that covers the steroid-binding site as well as others (Leu(171)-Lys(173) and Trp(84)) on the surface of human SHBG and may provide a basis for ligand-dependent interactions between SHBG and other macromolecules. These new crystal structures have also enabled us to construct a simple space-filling model that can be used to predict the characteristics of novel SHBG ligands.

Resolution of the human sex hormone-binding globulin dimer interface and evidence for two steroid-binding sites per homodimer

Human sex hormone-binding globulin (SHBG) transports sex steroids in the blood. It functions as a homodimer, but there is little information about the topography of its dimerization domain, and its steroid binding stoichiometry is controversial. The prevailing assumption is that each homodimeric SHBG molecule contains a single steroid-binding site at the dimer interface. However, crystallographic analysis of the amino-terminal laminin G-like domain of human SHBG has shown that the dimerization and steroid-binding sites are distinct and that both monomers within a homodimeric complex are capable of binding steroid. To validate our crystallographic model of the SHBG homodimer, we have used site-directed mutagenesis to create SHBG variants in which single amino acid substitutions (V89E and L122E) were introduced to produce steric clashes at critical positions within the proposed dimerization domain. The resulting dimerization-deficient SHBG variants contain a steroid-binding site with an affinity and specificity indistinguishable from wild-type SHBG. Moreover, when equalized in terms of their monomeric subunit content, dimerization-deficient and wild-type SHBGs have essentially identical steroid binding capacities. These data indicate that both subunits of the SHBG homodimer bind steroid and that measurements of the molar concentration of SHBG homodimer in serum samples have been overestimated by 2-fold.

Serum lipids, lipoproteins and sex-hormone binding globulin in breast cancer

Serum levels of various lipid parameters, i.e., triglycerides, total cholesterol, alpha lipoprotein or high density lipoprotein (HDL)-cholesterol and beta lipoprotein or low density lipoprotein (LDL)-cholesterol were measured in a total of 138 histologically proven cases of breast cancer along with 146 control women. The mean levels of serum triglycerides, total cholesterol and LDL-cholesterol were found to be significantly higher in breast cancer cases as compared to controls. However, lower mean levels of serum HDL-cholesterol and sex-hormone binding glubulin (SHBG) were observed in breast cancer patients than the control subjects. The results indicate a probable relation between serum lipids and the activity of sex-hormones. Moreover, the study reflects an overall disturbance of lipid metabolism in the pathological process of breast cancer.

Comparison of the lipoprotein, carbohydrate, and hemostatic effects of phasic oral contraceptives containing desogestrel or levonorgestrel

Desogestrel (DSG) is a less-androgenic progestogen than levonorgestrel (LNG). This difference in androgenicity may be responsible for observed differences in metabolic effects between oral contraceptive (OC) formulations containing almost equivalent estrogen doses but with either DSG or LNG as a progestogen. To test the hypothesis, a prospective 9-month randomized comparison of plasma lipids, glucose, insulin, hemostasis, and sex hormone binding globulin (SHBG) was conducted in 66 healthy women using phasic formulations of OCs containing either DSG (DSG-OC) or LNG (LNG-OC). The study results showed that SHBG increased 3-fold with DSG-OC and 2-fold with LNG-OC. DSG-OC increased HDL-C, HDL(2)-C and HDL(3)-C; LDL-C decreased transiently. LNG-OC decreased HDL(2)-C and increased HDL(3)-C; HDL-C was unchanged and LDL-C decreased transiently. Both formulations increased VLDL-C and triglycerides, more with DSG-OC, but apolipoprotein B levels increased equally. Apo A-I and A-II increased more with DSG-OC than with LNG-OC. Neither formulation altered Lp(a) or fasting glucose and insulin levels. Postprandially, both formulations decreased glucose and increased insulin responses, but to an equivalent degree. Both OCs slightly enhanced procoagulant and profibrinolytic parameters to the same extent except for internally compensating decreases in Factor V and protein S with DSG-OC. In summary, at almost equivalent estrogen doses, a phasic OC containing DSG compared with LNG has a less androgenic effect on lipoproteins and SHBG, similar effects on hemostatic parameters with lower protein S and factor V activity and equivalent effects on carbohydrate metabolism. The lipoprotein, SHBG, and protein S and factor V differences are likely due to the lesser androgenicity of DSG allowing for a greater expression of the dose of estrogen.

Characterization of the oligosaccharides of plasma sex hormone binding globulin from noncirrhotic alcoholic patients

In previous reports we have demonstrated high plasma levels of sex hormone-binding globulin (SHBG) in asymptomatic alcoholic men. In the present work the physicochemical properties of SHBG from plasma of noncirrhotic alcoholic patients have been further compared with SHBG of control subjects. Steroid binding to SHBG was similar for the two groups: alcoholic men, K(d) of 0.62 +/- 0.07 nM and control individuals, K(d) of 0.70 +/- 0.10 nM. The structure of oligosaccharides attached to SHBG from controls and alcoholic men were determined by using serial chromatography. Our data indicated that 7% of SHBG of control individuals was not retarded by the Con-A column, whereas approximately 30% of SHBG of alcoholic men eluted in the void volume of Con A. Approximately 46% of SHBG of alcoholics applied to Con A, possessed biantennary complex oligosaccharides, as indicated by the fact that it could be eluted with methyl-alpha-D-glucopyranoside and by its retention on wheat germ agglutinin; in contrast, when SHBG from control men was analyzed, approximately 51% was eluted with methyl-alpha-D-glucopyranoside. Approximately 9% of the biantennary complex oligosaccharides on SHBG of control men and none of those on SHBG from alcoholic men were fucosylated on the chitobiose core, as determined by chromatography on Lenn culinaris lectin. Galactosylated oligosaccharides were also present on the SHBG fraction as indicated by its interaction with Ricinus communis-I. Approximately 24% of SHBG of alcoholic men and 39% of those on SHBG from control individuals applied to Con-A were retained and could be eluted with methyl-alpha-D-mannopyranoside. Evidence based on the binding on mannoside-eluted SHBG to Con-A, wheat germ agglutinin, and R. communis-I indicated that at least the SHBG in this fraction, from alcoholics or controls, contained two glycosylation sites and that the sites were differentially glycosylated.

Expression and regulation of human sex hormone-binding globulin transgenes in mice during development

Human sex hormone-binding globulin (SHBG) is produced by hepatocytes and transports sex steroids in the blood. The rat gene encoding SHBG is expressed transiently in the liver during fetal life, but it is not expressed in the liver postnatally, and the small amounts of SHBG in rat blood are derived from gonadal sources. To study the biosynthesis and function of human SHBG in an in vivo context, we have produced several lines of transgenic mice that contain either 11 kb (shbg11) or 4.3 kb (shbg4) portions of the human shbg locus. The expression and regulation of these transgenes have now been studied during fetal and postnatal development. In situ hybridization of an shbg11 transgenic mouse fetus at 17.5 days postcoitus located human shbg transcripts only in duodenal epithelial cells and hepatocytes. Temporal differences in the hepatic expression of mouse shbg and human shbg transgenes during late fetal development were reflected in corresponding differences in mouse and human SHBG levels in fetal and neonatal mouse blood. Serum concentrations of human SHBG increased during the first weeks of life regardless of gender until about 20 days of age in shbg11 mice, but after this time they continued to increase only in the males. This sexual dimorphism was reflected in corresponding differences in human SHBG messenger RNA (mRNA) abundance in the livers of these animals. However, it was not observed in shbg4 mice, in which hepatic production of plasma SHBG continued to increase after puberty regardless of gender. Serum testosterone and SHBG levels correlated in all sexually mature shbg transgenic mice. Human shbg transcripts were detectable only in testes of shbg11 mice and increased progressively in abundance from 10 days of age until the animal reached sexual maturity at 30 days of age, with appreciable increases occurring well before any changes in serum testosterone concentration. In the kidney, SHBG mRNA levels accumulated earlier in shbg11 than in shbg4 mice, and the expression of both types of transgenes was sexually dimorphic, with much higher SHBG mRNA levels in the kidneys of male mice. As increases in SHBG mRNA in the male kidneys coincided with increases in serum testosterone during sexual maturation, we reasoned that shbg transgene expression is androgen dependent in the kidney. This was confirmed by demonstrating that a decrease in SHBG mRNA abundance in male mouse kidneys after castration could be reversed by 5alpha-dihydrotestosterone treatment. Moreover, exogenous androgen increased human SHBG mRNA levels in the kidneys of female mice. In summary, comparisons of how different human shbg transgenes are expressed in vivo provides information about the positions of potential regulatory sequences that may control the hormonal regulation and tissue-specific expression of this gene during development.

Serum leptin as an additional possible pathogenic factor in polycystic ovary syndrome

OBJECTIVES

Recent data raised the possibility that high leptin levels may contribute to infertility in some women with PCOS.

DESIGN AND METHODS

To assess changes in leptin levels and its relationship to some hormonal changes (insulin, testosterone, SHBG, FSH, LH, and prolactin) associated with PCOS in obese (n = 27) and nonobese (n = 18) patients when compared to obese and nonobese normal controls (n = 20).

RESULTS

Leptin concentration were significantly higher in PCOS than in controls, p < 0.05, with 81% sensitivity and 50% specificity. Whereas, high serum insulin levels were found in obese and nonobese women with PCOS, high serum leptin, FAI together with reduced SHBG were found in obese rather than nonobese PCOS women. Moreover, hyperleptinemia in PCOS women was not correlated to hyperinsulinemia (r = -0.13 and -0.4 in obese and nonobese PCOS women, respectively). In the patient's group correlation analysis between fasting serum leptin and different studied variables showed some correlation with body mass index (BMI) only (r = 0.413) suggesting that high leptin levels could be a characteristic of the obese PCOS. However, multiregression analysis showed that together with testosterone, leptin can successfully predict the presence or absence of PCOS.

CONCLUSION

The potential significance of leptin for the pathophysiology of PCOS will await direct studies of the effects of exogenous leptin and/or its inhibitors on the reproductive axis of women, including those with PCOS.

Photoaffinity labeling of homologous Met-133 and Met-139 amino acids of rabbit and sheep sex hormone-binding globulins with the unsubstituted Delta 6-testosterone photoreagent

Purified rabbit and sheep sex hormone-binding globulins (SHBGs) were photolabeled by Delta 6-testosterone. The maximal levels of specific incorporation were respectively 0.33 and 0.30 mol of label/mol of homodimer. Tryptic cleavage of photolabeled SHBGs gave a single radioactive peptide for rabbit SHBG and two major radioactive peptides S1 and S2 for sheep SHBG. Edman sequencing of the photolabeled peptide of rabbit SHBG revealed a single sequence corresponding to peptidic fragment Leu-118-Lys-134. Subcleavage of this peptide with elastase led to a single radioactive peptidic fragment corresponding to dipeptide Met-133-Lys-134, identified by mass spectrometry, while deletion of the C-terminal residue with carboxypeptidase B showed that all the radioactivity remained on peptide Leu-118-Met-133, thus demonstrating that photolabeling occurred exclusively on Met-133, the only residue common to the two radioactive subcleaved peptides. Edman sequencing of peptides S1 and S2 of sheep SHBG showed a same single sequence corresponding to residues Gln-126-Arg-140 which contained no identifiable phenylthiohydantoin derivative at cycle 14, thus indicating that in both cases the corresponding Met-139 residue is the main site of photolabeling, as confirmed for peptide S1 by the presence at this cycle of a major peak of radioactivity while in peptide S2 the photoattachment of Delta 6-testosterone was found labile in the conditions of sequencing. The photolabeled peptide S1 was characterized by mass spectrometry which showed the covalent fixation of one mole of Delta 6-testosterone and the presence of a biantennary oligosaccharide attached at Asn-133, which suggests that the steroid-binding site is probably not deeply buried in the SHBG homodimer.

A prospective study of endogenous serum hormone concentrations and breast cancer risk in premenopausal women on the island of Guernsey

The associations between serum concentrations of oestradiol, progesterone, testosterone and sex hormone-binding globulin (SHBG) and risk of breast cancer in premenopausal women were investigated in a prospective study of breast cancer on the island of Guernsey. Sixty-two women diagnosed with breast cancer an average of 8 years subsequent to blood collection were matched for day of menstrual cycle, age and year of blood collection with 182 control subjects. Cases had a 12% higher mean oestradiol concentration over the whole menstrual cycle (P = 0.17) with a large difference at mid-cycle (75% higher, P = 0.04). Differences between cases and control subjects in progesterone (luteal phase), testosterone and SHBG were small and not statistically significant: luteal phase progesterone 9% lower in cases, P = 0.64; testosterone 4% higher, P = 0.57; SHBG 8% higher, P = 0.24. The small difference in oestradiol concentration could be aetiologically important, but larger prospective studies are needed.

A prospective study of endogenous serum hormone concentrations and breast cancer risk in post-menopausal women on the island of Guernsey

The associations between serum concentrations of oestradiol, testosterone and sex hormone-binding globulin (SHBG) and risk of breast cancer in post-menopausal women were investigated in a prospective study on the island of Guernsey. Sixty-one women who developed breast cancer an average of 7.8 years after blood collection were matched for age, year of blood collection and number of years post-menopausal with 179 control subjects. Women using exogenous hormones at the time of blood collection were excluded from the study. Women who subsequently developed breast cancer had a 29% higher geometric mean oestradiol concentration than control women (P = 0.004). The odds ratio for breast cancer in the top third compared with the lowest third of the oestradiol concentration distribution was 5.03 (95% confidence interval 2.02-12.49, P for trend < 0.001). Adjusting for testosterone and SHBG concentrations did not substantially alter the odds ratio for oestradiol. Although testosterone and SHBG concentrations were associated with breast cancer risk, the concentrations of these hormones were correlated with those of oestradiol; the associations were not statistically significant after adjusting for oestradiol concentration. These data provide evidence that serum oestradiol concentrations in post-menopausal women may have a substantial effect on breast cancer risk.

Diurnal variation of sex hormone binding globulin and insulin-like growth factor binding protein-1 in women with polycystic ovary syndrome

OBJECTIVES

The aim of this study was to examine (1) the diurnal variation in SHBG and (2) the inter-relationships of insulin, IGF-I, SHBG and IGFBP-1 over 24 hours in 10 women with anovulatory PCOS and compare them with weight-matched ovulatory controls.

PATIENTS AND METHODS

The two groups comprised 10 anovulatory women with PCOS (as defined by clinical, ultrasound and biochemical criteria) and 10 weight matched controls. Serum samples were taken at two-hourly intervals for 24 hours and stored for measurement of SHBG, IGFBP-1, insulin and IGF-I. Differences between the groups were compared using the Wilcoxon ranked paired tests of the individual peak and trough concentrations in each group. The variation in insulin, IGFBP-1 and SHBG concentrations over 24 hours was tested using two-way analysis of variance with the factors time and subject. Spearman's correlation coefficient was calculated from the subjects' median value over 24 hours.

RESULTS

The median (interquartile range) body mass index (BMI) was 25.2 (22.2-29.3) in the PCOS group and 24.3 (23.2-25.7) kg/m2 in the control group. Serum testosterone (T) and LH levels were significantly raised in the PCOS group compared to the control group; T 3.8 (2.9-5.6) vs 1.9 (1.9-2.5) nmol/l (P < 0.007) and LH 12 (10-15) vs 4.1 (3.6-4.5) IU/I (P < 0.005) respectively. There was no diurnal variation in SHBG. The median (interquartile ranges) of the peak SHBG concentrations was lower in the PCOS group: 29.4 (14.9-39.4) vs 52.1 (39.4-61) nmol/l in the control group (P < 0.01). The fasting levels of insulin at 0600 h (median (interquartile ranges)) were not significantly different between the groups; 6.6 (5.4-9.8) and 6.2 (1.9-7.6) mU/l, respectively, although the peak median concentrations were significantly different; PCOS 66.1 (50.9-129.2) vs 40 (36.1-74.2) mU/l (P < 0.05). Two-way analysis of variance showed a diurnal variation in insulin concentrations in the control group (P = 0.001) but not in the PCOS group (P = 0.1). The diurnal variation in IGFBP-1 was similar in the two groups but the peak median levels were lower in the women with PCOS 54.9 (22.3-79.2) vs 71.5 (60.5-99.3) micrograms/l (P < 0.03). The decline in IGFBP-1 concentrations correlated with the increase in insulin concentrations. The IGF-I concentrations were similar in the two groups. There was a significant negative correlation between SHBG and insulin (P < 0.05) and between insulin and IGFBP-1 (P < 0.01).

CONCLUSION

This study demonstrates that there is no diurnal variation in SHBG concentrations and confirms the finding of a marked diurnal variation in the concentration of IGFBP-1. Women with PCOS who are anovulatory have an abnormal pattern of insulin secretion with an absence of diurnal variation compared to weight matched controls. This provides further evidence of the relative insulin resistance which is independent of weight found in women with anovulatory PCOS. The inverse correlations of insulin concentrations with SHBG and IGFBP-1 support the role of insulin as a possible regulator of the circulating levels of these binding proteins although the difference in the time course of their response makes it unlikely that they are co-regulated.

Sex hormone-binding globulin/androgen-binding protein: steroid-binding and dimerization domains

Plasma sex hormone-binding globulin (SHBG) and testicular androgen-binding protein (ABP) are homodimeric glycoproteins that share the same primary structure, and differ only with respect to the types of oligosaccharides associated with them. The biological significance of these differences is not understood, but enzymatically deglycosylated SHBG and a non-glycosylated SHBG mutant both bind steroids normally. Various affinity-labelling experiments, and studies of recombinant SHBG mutants have indicated that a region encompassing and including Met-139 in human SHBG represents an important component of its steroid-binding site. Analyses of chimeric proteins comprising various portions of human SHBG and rat ABP have also indicated that residues important for the much higher affinity of human SHBG for steroid ligands are probably located within the N-terminal portion of these molecules. Recent studies of SHBG mutants have confirmed this, and a deletion mutant containing only the first 205 N-terminal residues of human SHBG has been produced which dimerizes and binds steroids appropriately. The introduction of amino-acid substitutions between Lys-134 and Phe-148 of SHBG has also indicated that residues including and immediately N-terminal of Met-139 may influence steroid-binding specificity, while those immediately C-terminal of Met-139 represent at least a part of the dimerization domain. These studies have also demonstrated that dimerization is induced by the presence of steroid ligand in the binding site, and that divalent cations play an important role in this process. Together, these data have led us to conclude that SHBG is a modular protein, which comprises an N-terminal steroid-binding and dimerization domain, and a C-terminal domain containing a highly-conserved consensus sequence for glycosylation that may be required for other biological activities, such as cell-surface recognition.

Hemostatic, metabolic, and androgenic risk factors for coronary heart disease in physically active and less active postmenopausal women

Physically active postmenopausal women have a lower incidence of coronary heart disease (CHD) than their more sedentary peers, but little information is available concerning the responsible mechanisms. The primary aim of this study was to test the hypothesis that physically active post-menopausal women demonstrate more favorable levels of hemostatic, metabolic, and androgenic CHD risk factors than less active control subjects. If so, a secondary aim was to determine which of the characteristics associated with a physically active lifestyle, ie, low body fat, a high-carbohydrate/low-fat diet, high maximal aerobic capacity (aerobic fitness), and high levels of physical activity, are most closely related to this lower risk profile. To address these aims, we compared CHD risk factors in physically very active women (n = 14; age, 55 +/- 2 years) with those in healthy, nonobese sedentary control subjects (n = 17; age, 56 +/- 1 years). Maximal aerobic capacity (fitness) was 83% higher (P < .001) in the physically active women. Concentrations of plasminogen activator inhibitor type 1 activity and tissue plasminogen activator antigen were lower (more favorable) (P < .005) in the physically active women versus control subjects, whereas plasma fibrinogen levels did not differ. The physically active women had lower (P < .01) fasting plasma insulin and glucose concentrations as well as smaller responses to an oral glucose challenge. Both total-body and abdominal fat levels were lower (P < .001) and lipid and lipoprotein profiles were generally more favorable (P < .05) in the physically active women.(ABSTRACT TRUNCATED AT 250 WORDS)

Age related changes in the pituitary-testicular axis in normal men; lower serum testosterone results from decreased bioactive LH drive

OBJECTIVE

The mechanism underlying the slight hypoandrogenism associated with normal ageing remains unclear. We have therefore examined age related changes in the activity of the pituitary-testicular axis in healthy normal males.

DESIGN

Random blood samples were obtained from 219 normal men whose ages ranged from 20 to 79 years. At the time of the study, none of the men had received treatment or had ever had any endocrine dysfunction diagnosed.

MEASUREMENTS

Luteinizing hormone was measured in the subjects' plasma using a commercially available immunoradiometric assay (IRMA, Serono Maiaclone) and a fully validated in-vitro bioassay. Testosterone and FSH were measured using standard radioimmunoassays (RIA) whilst sex hormones binding globulin was assayed by an IRMA.

RESULTS

Levels of total testosterone (total-T) and bioactive LH fell with age (r = -0.231 and -0.189 respectively) by 5.9 nmol/l and 2.3 IU/l respectively between grouped patients aged 20-39 years (Group A) and 60-79 years (Group C). In contrast, immunoreactive LH remained unchanged. The LH B:I ratio also fell with age (P < 0.0001) being 5.0 +/- 0.3 (group A) and 3.3 +/- 0.2 (group C), representing a fall of 33%. Since immunoreactivity remained constant, this fall primarily represented the decline in LH bioactivity. Bioactive, but not immunoreactive LH correlated to total-T (P = 0.009, n = 209) and the total-T:LH ratios fell by over 30% between groups A and C using the IRMA, but remained unchanged by bioassay.

CONCLUSIONS

There is an underlying decline in both total-testosterone and free-testosterone index, and bioactive LH levels with advancing age, suggestive of a hypothalamo-pituitary defect which leads to lower bioactive LH levels which in turn are responsible for the diminished gonadal steroidogenesis. Elucidation of the mechanism underlying this slight decline in hypothalamopituitary testicular activity is complicated by differences between the data obtained by immunoassay or bioassay.

Resolution of the steroid-binding and dimerization domains of human sex hormone-binding globulin by expression in Escherichia coli

To determine the minimal sequence requirements for steroid binding and dimerization of human sex hormone-binding globulin (SHBG), the SHBG polypeptide and various SHBG deletion mutants were expressed as glutathione S-transferase (GST) fusion proteins in Escherichia coli. Fusion proteins containing the complete SHBG sequence, or the first 177 N-terminal residues of SHBG, bound steroids with high affinity and specificity. Further deletions from the C-terminus severely compromised steroid-binding activity, as did N-terminal deletions beyond residue 18 in the SHBG sequence. Thus, residues 18-177 in SHBG encompass a region required for its steroid-binding activity, and a disulfide bridge normally present between Cys-164 and Cys-188 in SHBG is not obviously essential for steroid binding. Most of the GST/SHBG fusion proteins undergo cleavage at 4 degrees C, releasing immunoreactive polypeptides that correspond approximately in size to their respective SHBG sequences. The 23-kDa immunoreactive cleavage product released from the fusion protein containing residues 1-205 in the SHBG sequence (SHBG 1-205) has a 50-fold greater steroid-binding capacity but a 7.5-fold lower affinity than its parent fusion protein. In addition, the 22-kDa immunoreactive polypeptide released from SHBG(1-194) binds steroid, and its dimerization is promoted by steroid ligands that bind SHBG with high affinity. These data suggest that the N-terminal region of SHBG dimerizes readily in the absence of GST and in doing so acquires steroid-binding sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum distribution of two contraceptive progestins: 3-ketodesogestrel and gestodene

A cross-over study of two oral contraceptive formulations, containing 30 micrograms ethinylestradiol in combination with 150 micrograms desogestrel (Marvelon) or 75 micrograms gestodene (Femovan), has been performed to compare the serum distribution and pharmacokinetics of gestodene and the active metabolite of desogestrel, namely 3-ketodesogestrel. Serum concentrations of both sex hormone-binding globulin (SHBG) and corticosteroid-binding globulin (CBG) were also measured and were increased more than 3-fold and 2-fold, respectively, on day 21 of the treatment cycle, with no statistically significant difference between treatment groups. In addition, 35 days after ingestion of either oral contraceptive had ceased, the serum SHBG and CBG concentrations were similar to the pretreatment values. During treatment cycles, increased serum SHBG levels were associated with a redistribution of 3-ketodesogestrel and gestodene such that the non-protein-bound (NPB) and albumin-bound fractions were reduced in concert with an increase in the relative proportions bound to SHBG. The proportion of gestodene bound to SHBG was consistently higher than that observed for 3-ketodesogestrel, and this undoubtedly reflects the higher affinity of SHBG for gestodene (Kd = 1.2 nM at 37 degrees C) when compared to 3-ketodesogestrel (Kd = 4.7 nM at 37 degrees C). It also probably accounts, in part, for the much higher total serum levels of gestodene (8.58 nmol/L) when compared to 3-ketodesogestrel (2.37 nmol/L) during the treatment cycles. Consequently, the absolute amounts of NPB, non-SHBG-bound, and SHBG-bound gestodene are significantly higher than those measured for 3-ketodesogestrel. It is concluded that ethinylestradiol-induced increases in serum SHBG levels during treatment with Marvelon or Femovan, influenced the distribution and total amount of 3-ketodesogestrel and gestodene in serum, respectively, and that this, combined with the higher affinity of SHBG for gestodene, results in a greater amount of bioavailable gestodene compared to 3-ketodesogestrel, despite the smaller dose of gestodene administered.

Structure, function, and regulation of androgen-binding protein/sex hormone-binding globulin

Despite over 20 years of research, the functions of ABP and SHBG remain elusive. The major reason for this lack of knowledge has been the unavailability of natural mutants with clinical defects for study. There is strong evidence that these binding proteins do act to modulate the gene regulatory actions of nuclear sex steroid receptors by controlling the availability of androgens and estrogens. In plasma, SHBG controls the metabolic clearance rate of sex steroids. In addition there is strong evidence that they have a much broader function. The identification of plasma membrane receptors in target tissues and the finding of homologous domains in several developmental proteins support other functions. Moreover, other experiments suggest the proteins may actually be hormones or growth factors. These findings are not compatible with a model that has the proteins only regulating free steroid hormone levels. Obviously, much more experimentation will be necessary to reveal the functions of ABP and SHBG. The recent discoveries have offered several clues to their functions and open new routes for study. These experiments, coupled with newly developed techniques, such as gene knockout by homologous recombination, make one optimistic that the functions of these unique proteins will be deciphered in the near future.

Beneficial effects on serum lipoproteins by 17 beta-oestradiol-dydrogesterone therapy in postmenopausal women; a prospective study

STUDY OBJECTIVE

To study the possible changes of reproductive hormones, sex hormone binding globulin, serum lipids and lipoproteins, lipoprotein (a) included, coagulation and glucose in postmenopausal women treated with 17 beta-oestradiol and cyclic dydrogesterone for 14 days per 28 days treatment cycle.

DESIGN

Open longitudinal prospective study.

DURATION

Twelve 28 days treatment cycles.

SETTING

Gynaecological department of university hospital.

SUBJECTS

27 healthy postmenopausal women.

RESULTS

After treatment for six cycles serum concentrations of FSH and LH decreased significantly with 43.0% and 24.4%, respectively. Serum concentrations of 17 beta-oestradiol and oestrone increased significantly with 302% and 792%, respectively, and SHBG increased as well with 111% (P < 0.01). Serum total cholesterol decreased with 9.0% (P < 0.01). Serum VLDL-cholesterol did not change significantly. Serum LDL-cholesterol decreased with 16.3% (P < 0.01) and HDL-cholesterol increased with 8.0% (P < 0.01). This was accompanied with similar significant changes in the apolipoproteins: apolipoprotein A-I rose with 14.4% and apolipoprotein B decreased with 6.0%. Serum triglycerides and VLDL-triglycerides increased significantly with 14.4% and 17.9%, respectively. Lipoprotein (a) decreased with 17.5% (P < 0.01). These results more or less sustained at cycle 12 of treatment. Serum concentrations of antithrombin III and glucose did not change. Fibrinogen decreased slightly but significantly below the initial value.

CONCLUSIONS

This combination replacement therapy gives beneficial changes in lipid-metabolism, indicating a reduced risk of developing coronary heart disease without unfavourably changing coagulation and glucose metabolism. The expected beneficial changes with oestradiol alone are not counteracted by the intermittent addition of dydrogesterone. Therefore this oestrogen/progestagen scheme can, indeed, be recommended for use in HRT.

Two-sites immunoradiometric assay using monoclonal antibodies for the determination of serum human sex hormone binding globulin

An immunoradiometric assay (IRMA) for the determination of human Sex Hormone Binding Globulin (SHBG) in serum is described. This IRMA uses three mouse monoclonal antibodies. Two monoclonals anti-human SHBG are coated on tubes and used as capture antibodies. The third monoclonal labeled with 125I completes the system, allowing the formation of the "sandwich". The detection limit of the assay is 2.5 femtomol SHBG per tube (250 pg/tube). Using this test for the measurement of SHBG and radioimmunoassays for the determination of total Testosterone and Estradiol, we calculated the Free Androgen Index (FAI) and the Free Testosterone. The results obtained were compared with the values of Free Testosterone measured by equilibrium dialysis. There is a close correlation between both calculated parameters and the levels of Free Testosterone, validating this SHBG assay.

Characterization of Met-139 as the photolabeled amino acid residue in the steroid binding site of sex hormone binding globulin using delta 6 derivatives of either testosterone or estradiol as unsubstituted photoaffinity labeling reagents

Immunopurified human sex hormone binding globulin (SHBG) was photoinactivated and photolabeled by radioinert and radioactive photoaffinity labeling steroids delta 6-testosterone (delta 6-T) and delta 6-estradiol (delta 6-E2). The maximal levels of specific incorporation of these two reagents were 0.50 and 0.33 mol of label/mol of SHBG, respectively. Covalently labeled SHBG fractions were citraconylated, reduced, carboxymethylated, and cleaved by trypsin. Separation of tryptic digests by reverse-phase liquid chromatography gave single radioactive peaks at the same retention times with both steroid reagents. However, the two labeled peptidic fractions could be distinguished by capillary electrophoresis and immunodetection with anti-steroid antibodies, whereas the covalent attachment of radioactivity was confirmed by thin-layer chromatography on silica gel. Edman degradation of the two labeled peptides showed a single sequence His-Pro-Ile-([3H]X)-Arg corresponding to the pentapeptide His-Pro-Ile-Met-Arg 136-140 of SHBG sequence. The coincidence, in both cases, of the absence of an identifiable amino acid residue and of the elution of the most intense peak of radioactivity at the fourth cycle of Edman degradation suggests that the same Met-139 residue was labeled by delta 6-[1,2-3H2]T or by delta 6-[17 alpha-3H]E2. Liquid secondary ion mass spectrometry of the two peptides showed [M+H]+ ions at m/z 939.8 or 923.8, corresponding respectively to the addition of delta 6-T or delta 6-E2 to the pentapeptide. The presence of the steroid molecule in the delta 6-[3H]T-pentapeptide conjugate was confirmed by the difference of 2 mass units with the [M+H]+ peak of the delta 6-[4-14C]T-pentapeptide conjugate.

Structure/function analyses of human sex hormone-binding globulin by site-directed mutagenesis

Human sex hormone-binding globulin (hSHBG) and rat androgen-binding protein (rABP) exhibit distinct affinities for sex-steroids. We therefore constructed and expressed a hSHBG/rABP hybrid cDNA encoding the N-terminal portion of hSHBG (205 residues) and the C-terminal portion of rABP (168 residues). The resulting chimera displayed similar steroid-binding characteristics as hSHBG and was recognised by a monoclonal antibody (S1B5) for hSHBG. We then created substitutions at Ser-133, His-136 and Met-139. The Asp-133 and Gln-136 mutants bound steroids in the same way as normal hSHBG while the steroid-binding affinity of Trp-139 was reduced. All three mutants cross-reacted similarly in a hSHBG radioimmunoassay, but Gln-136 was recognised poorly by the S1B5 antibody. These data imply that residues involved in steroid-binding are located within the N-terminal half of hSHBG and include Met-139, and that the S1B5 epitope is located in this region.

A method for the determination of sex hormone binding globulin using Concanavalin A-sepharose

A binding assay for sex hormone binding globulin (SHBG) has been developed in which SHBG is saturated with tritiated dihydrotestosterone (DHT). Separation of bound and free DHT is achieved by using Concanavalin A-Sepharose as a solid phase matrix. The method is described and its performance, including linearity, imprecision and comparison with other methods, is assessed. The assay is simple and robust and is suitable for analysis of samples of plasma or serum for clinical or research use.

A prospective study of obesity, lipids, apolipoproteins and ischaemic heart disease in women

The aim of the study was to examine the relationships of obesity, lipids and apolipoproteins with the risk for subsequent ischaemic heart disease in middle-aged women, using a case-control study nested within a cohort study. A total of 3634 women aged 26-88 were recruited in Guernsey between 1977 and 1985 and followed until June 1986 by abstraction of their general practitioners' records. Fifty-one cases of incident ischaemic heart disease (11 myocardial infarction, 40 angina) were identified. For each case up to 4 controls were selected, matched for age and date at recruitment. Odds ratios for the development of ischaemic heart disease in the middle and upper thirds of the distribution for each variable in the controls, relative to the lowest third (and two-sided P-values for linear trends), were: 3.0, 2.6 (0.015) for Quetelet's index; 3.3, 5.1 (0.003) for total cholesterol; 0.5, 0.6 (0.102) for apolipoprotein A-I; 1.8, 2.4 (0.015) for apolipoprotein B; 1.3, 2.1 (0.155) for apolipoprotein(a). The increased risks associated with increased Quetelet's index and total cholesterol were independent of each other and these variables were more strongly related to myocardial infarction than to angina. The relationships of risk with serum cotinine, fatty acids, dehydroepiandrosterone sulphate and sex hormone binding globulin were weak and did not approach statistical significance.

Endocrine effects in female weight lifters who self-administer testosterone and anabolic steroids

It appears that the self-administration of testosterone and anabolic steroids is increasingly practiced by women in sports where strength and endurance are important. We recently evaluated endocrine parameters in nine female weight lifters using steroids and seven not using these agents. Of the nine anabolic steroid users, seven took multiple anabolic steroids simultaneously. Thirty-fold elevations of serum testosterone were noted in the women injecting testosterone. In three of these women serum testosterone levels exceeded the upper limits for normal male testosterone concentrations. A significant compensatory decrease in sex hormone-binding globulin and a decrease in thyroid-binding proteins were noted in the women steroid users. Also, a 39% decrease in high-density lipoprotein cholesterol was noted in the steroid-using weight lifters. Most of the subjects in this study used anabolic steroids continuously, which raises concern about premature atherosclerosis and other disease processes developing in these women.

Cigarette smoking and steroid hormones in women

Epidemiological evidence has suggested that cigarette smoking has an anti-oestrogenic effect in women, but the effects of smoking on steroid hormone metabolism are not fully understood. We compared serum concentrations of oestradiol, progesterone (luteal phase) and dehydroepiandrosterone sulphate (DHEA-S), and urinary excretion rates of six steroids of predominantly adrenal origin, in healthy premenopausal and postmenopausal female smokers and non-smokers. Serum concentrations of oestradiol, progesterone and DHEA-S did not differ between smokers and non-smokers by greater than 5%, and none of these differences was statistically significant. Mean urinary excretion rates of androsterone, aetiocholanolone, DHEA, 11-keto-aetiocholanolone, 11-hydroxyandrosterone and 11-hydroxyaetiocholanolone were very similar in smokers and non-smokers in premenopausal women, but were from 2-44% higher in smokers than non-smokers in postmenopausal women. The difference was statistically significant only for 11-hydroxyandrosterone. These results confirm previous reports that cigarette smoking does not affect serum oestradiol in premenopausal or postmenopausal women, but provide only weak evidence to support previous findings of increased levels of some adrenal steroids in postmenopausal women smokers. The mechanism for the apparent anti-oestrogenic effect of cigarette smoking remains unclear.

Hirsutism: metabolic effects of two commonly used oral contraceptives and spironolactone

Fifty-one hirsute women were randomly treated for nine months with ethinyl estradiol 35 ug plus norethindrone 0.4 mg or 30 ug ethinyl estradiol plus 1.5 mg norethindrone acetate if they needed contraception or spironolactone 200 mg daily if they did not. Metabolic evaluations in response to therapy demonstrated triglyceride elevations with the two oral contraceptives but not with spironolactone. While systolic blood pressure was lower with spironolactone, fasting insulin levels were higher as opposed to either low-dose oral contraceptive preparation. Ethinyl estradiol 30 ug plus 1.5 mg norethindrone acetate lowered 3-alpha-diol glucuronide levels, yet ethinyl estradiol 35 ug plus norethindrone 0.4 mg and spironolactone were more effective in lowering Ferriman-Gallwey Scores. Treatment strategies for hirsute women need to consider metabolic consequences as well as efficacy.

Plasma sex hormone binding globulin in patients with prostatic carcinoma

The concentrations of sex hormone binding globulin (SHBG) were measured in the plasma of 56 men, who were 47 to 85 years of age, by time-resolved immunofluorometric assay with a monoclonal antibody. Twenty-five of the men had untreated carcinoma of the prostate and 17 had untreated prostatic hyperplasia. There were 14 healthy control subjects. SHBG levels were significantly higher in patients with prostatic carcinoma (37.6 +/- 8.4 nmol/l) than in those with prostatic hyperplasia (24.5 +/- 5.2 nmol/l; P less than 0.05) or control subjects (14.9 +/- 2.8 nmol/l; P less than 0.01). It is not known why SHBG levels are higher in patients with carcinoma or hyperplasia of the prostate. The contradictory results obtained in other studies may be due to heterogeneity of the binding globulin causing its values to vary in the different assays used.

Luteinizing hormone pulsatility in men with damage to the germinal epithelium

Bioactive-LH (B-LH) was measured in plasma by in-vitro bioassay and immunoactive-LH (I-LH) by immunoassay at 10 min intervals for 6 h in five men after standard chemotherapy for Hodgkin's disease. Eleven normal men acted as controls. Follicle-stimulating hormone (FSH) was markedly raised in the treated patients (mean +/- SEM; 12.8 +/- 2.8 vs. 2.7 +/- 0.4 IU l-1, P less than 0.006) reflecting damage to the germinal epithelium. Bioactive (27.4 +/- 2.8 vs. 12.9 +/- 1.3 IU l-1) and I-LH (9.6 +/- 2.0 vs. 4.9 +/- 0.4 IU l-1) were elevated (P less than 0.006) in the patient group whilst testosterone levels (24.0 +/- 3.8 vs. 19.6 +/- 2.4 nmol l-1) were normal. The testosterone I-LH ratio, a putative index of Leydig cell dysfunction, was negatively correlated with FSH levels (r = -0.85, P less than 0.02). Bioactive and I-LH pulse peak amplitude were elevated, as were pulse maxima (P less than 0.05). In contrast, B-LH pulse frequency was similar between the patients (2 pulses per 6 h) and controls (median 2, range 1-3 pulses per 6 h) as was the I-LH pulse frequency (median 2, 1-2 pulses per 6 h in both groups). The mean B:I LH ratios were similar (2.94 +/- 0.09 vs. 2.63 +/- 0.14) in both groups, although the inter-pulse B:I ratio was increased (P less than 0.007) in the patient group.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between CA 125 and progesterone production in women with ovarian carcinoma

CA 125 and steroid production is compared in a group of 48 women with ovarian epithelial carcinoma. The histologic types were I C (n = 20), II C (n = 5), III C (n = 11), or V (n = 12). The number of patients in Stage I was six; Stage II, 11; Stage III, 16; and Stage IV, 15. All patients were naturally or surgically postmenopausal. Blood samples were taken at the first admission to the hospital and 14 cases with large tumors were followed with monthly sampling during chemotherapy, and in 13 cases until a recurrence of the tumor. CA 125 and steroid production were analyzed using radioimmunoassay. The results show a high correlation between initial CA 125 and especially progesterone plasma concentration. Both decreases during chemotherapy parallel the shrinkage of the tumor and increase 1 to 4 months before recurrence. Progesterone and CA 125 together predicted all recurrences but none of the factors alone. The prognostic value for 5-year survival was somewhat higher for progesterone than CA 125. CA 125 correlated highly with sex hormone binding globulin (SHBG) and negatively with albumin. The correlation may be due to the intercorrelation with tumor burden.

The relationship of free fatty acids with the binding of oestradiol to SHBG and to albumin in women

Free fatty acid concentration, sex hormone binding globulin (SHBG) concentration, % free oestradiol and % SHBG-bound oestradiol were measured in fasting and non-fasting serum samples from 48 women. Free fatty acids were 128% higher (P less than 0.001) and % SHBG-bound oestradiol was 11% lower (P = 0.001) in fasting than non-fasting samples, but these changes were not significantly correlated (r = -0.16, P = 0.287). Mean SHBG concentration and % free oestradiol did not differ significantly between fasting and non-fasting samples. Between subject correlations were calculated for measurements from 30 premenopausal women: % free oestradiol was inversely correlated with SHBG and free fatty acids and positively correlated with Quetelet's Index; % SHBG-bound oestradiol was positively correlated with SHBG but was not consistently or significantly related to free fatty acids or Quetelet's Index. It was concluded that physiological increases in free fatty acid concentrations do not increase % free oestradiol and that free fatty acids are less important than SHBG concentration and perhaps other variables in determining differences between individuals in oestradiol binding to SHBG.

Estimation of serum sex hormone-binding globulin by five direct and two indirect methods

Serum sex hormone-binding globulin (SHBG) has been estimated over the range 2-190 nM by six commercially available methods. The Farmos immunoradiometric assay (IRMA) and the Pharmacia-LKB DELFIA fluoroimmunoassay, which use the same monoclonal antiserum, produced statistically identical but widely spread results. The Techland polyclonal radioimmunoassay produced similar results but was considerably less sensitive, and agreement with the other two direct methods was poor at low concentrations. These three direct methods gave slightly higher results than those obtained with the two indirect methods: the BioMerieux concanavalin-A-binding method and, especially, the Serono ammonium sulphate precipitation method. The Diagnostic Products monoclonal IRMA gave results that were up to double the values obtained with the other five methods and is considered unsatisfactory. Monoclonal antibodies are now available for the direct estimation of SHBG, although an amino acid sequence has not yet been published for this protein, and there is still some controversy about the size of its structural units.

Circulating sex hormone-binding globulin and testosterone in newborns and infants

The concentrations of sex hormone-binding globulin (SHBG) and testosterone (T) were measured in the cord blood of full-term newborns (14 boys, 15 girls) and pre-term newborns (10 boys, 5 girls), and in the venous circulation of 100 full-term infants aged 1-204 days. The ratio of T to SHBG (the 'free androgen index', FAI) was calculated to reflect the level of unbound T (the free, biologically active fraction). In boys' umbilical cord sera, T concentrations were significantly greater in arterial than in venous sera, while there was no such difference in the concentration of SHBG. Levels of SHBG in cord sera were considerably lower than those seen in the maternal circulation at term, but they were significantly greater in boys' than in girls' cord sera. Levels of T, and the FAI, were significantly greater in boys' arterial cord sera than in girls'. In early infancy, SHBG concentrations rose in both sexes, the highest values being seen in girls. In infant girls, levels of T and the FAI were constantly low. In infant boys, the expected peak in serum T concentrations was observed at 1-3 months the values approaching those seen in men. In contrast, values of the FAI at this age were relatively low, similar to those seen in women. This suggests that the elevation of male serum T during the first months of life lacks biological significance. However, it is important to realise that the FAI in male infants is about one order of magnitude larger than that in female infants at this time.

The relationships of SHBG with current and previous use of oral contraceptives and oestrogen replacement therapy

Sex hormone binding globulin (SHBG) concentration was measured in serum samples from 2077 premenopausal and 901 naturally postmenopausal women who had no history of disease or of recent drug use likely to affect SHBG. Current users of oral contraceptives (OCs) and of oestrogen replacement therapy had higher mean SHBG values than non-current users. Both premenopausal and postmenopausal women who had previously used OCs had a lower mean SHBG concentration than never users of OCs. Previous use of oestrogen replacement therapy was not related to SHBG.

Endogenous steroids in the pathophysiology of breast cancer

The search for major endocrine abnormalities as causes for breast cancer has not been successful, whether it has been directed at patients with this disease or at different groups or populations at risk. An early-onset, long-lasting ovulatory cycle function seems to be prevalent in different risk categories for breast cancer. Women with early menarche, compared with those with late menarche, are additionally characterized as having higher circulating estradiol and lower sex-hormone-binding globulin concentrations. A number of additional findings point to estradiol as a central agent in the development of breast cancer, and cyclic progesterone secretion does not seem to have a clearly opposing action.

The distribution of estradiol in the sera of normal Caucasian, Chinese, Filipina, Hawaiian and Japanese women living in Hawaii

Mean concentrations of sex-hormone-binding-globulin (SHBG) and the percentage distribution of estradiol between the non-protein-bound, albumin-bound and SHBG-bound fractions were not different in Caucasian, Hawaiian, Chinese, Japanese and Filipinas living in Hawaii. The widely varying incidence rates for breast cancer are therefore not explained by variations in the availability of estradiol.