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Organochlorines and bone mineral density in Swedish men from the general population.

Persistent organochlorines (POCs), such as polychlorinated biphenyls (PCBs) and DDT, are present at relatively high concentrations in food and show estrogenic, anti-estrogenic or anti-androgenic activity in biological test systems. Because bone mineral density (BMD) in men is influenced by sex hormones, we looked for associations between BMD and serum concentrations of POCs in 115 men (mean age 63 years, range 40-75 years) from the general Swedish population. Ten PCB congeners, five DDT isomers, hexachlorobenzene, three hexachlorocyclohexane isomers, trans-nonachlor and oxychlordane were analyzed by gas chromatography. Quantitative bone measurements were performed by dual-energy X-ray absorptiometry at three sites: whole body, the L2-L4 region of the lumbar spine, and the neck region of the proximal femur, as well as by quantitative ultrasound on the left os calcis (broadband ultrasound attenuation (BUA) and speed of sound (SOS)). After adjustment for confounding factors in linear regression analyses we found no strong association between serum concentrations of single POCs and the five BMD and ultrasound variables. When POCs were grouped according to hormonal activity (estrogenic, anti-estrogenic, anti-androgenic) and the study subjects were divided into organochlorine concentration quartiles, a weak association was indicated between increased serum concentrations of p,p'-DDE (antiandrogenic) and decreased BMD, BUA and SOS. This may suggest that p,p'-DDE could cause negative effects on bone density, but the findings might also be due to chance since multiple comparisons were made in the statistical analysis. Overall our results do not suggest that the studied POCs caused major effects on bone density in our study group.

Adult↗

Gender differences in renal tubular taurocholate transport.

The bile acids filtered through the glomeruli nearly completely escape urinary excretion due to an efficient tubular reabsorption process. Reabsorption is mediated by the sodium-dependent bile acid transporter ASBT, which is localized in the brush border membranes of proximal tubular cells. The purpose of the present study was to assess whether tubular taurocholate transport is regulated by sex hormones. Clearance studies and studies on proximal tubular cells freshly isolated from rat kidneys were performed. The studies with the isolated proximal tubular cells revealed a cell to bath 3H-taurocholate accumulation ratio of 5.63+/-0.28 in male and of 3.67+/-0.43 in female rats (p<0.01). This difference in cellular taurocholate uptake was corroborated by the clearance studies, which showed a 3H-taurocholate clearance of 133.9+/-28.1 in male rats and of 262.0+/-45.4 microl/min x 100 g b.w. in female rats (p<0.05). Testosterone treatment of female rats did not significantly alter the cell to bath 3H-taurocholate accumulation ratio. However, the cellular taurocholate accumulation significantly decreased, by 61.6+/-10.1%, following ethinylestradiol treatment of male rats. Ovariectomy, chemical castration of female rats with buserelin or treatment of female rats with the estrogen receptor antagonist ICI 182780 did not affect taurocholate uptake, but treatment of ovariectomized rats with ethinylestradiol decreased the taurocholate accumulation ratio by 53.7+/-15.8%. By determination of serum bile acids the possibility was excluded that this change was an indirect effect of cholestasis induced by ethinylestradiol. This study demonstrates gender differences in the renal handling of taurocholate in rats that may be related to an inhibitory effect of estrogens on taurocholate transport in proximal tubular cells. Since the ASBT protein content of the proximal tubular cells was found not to be different between male and female rats, a nongenomic mechanism may underly this estrogen effect.

Androgens↗

Antiremodeling agents influence osteoblast activity differently in modeling and remodeling sites of canine rib.

Antiremodeling agents reduce bone loss in part through direct actions on osteoclasts. Their effects on osteoblasts and bone formation activity are less clear and may differ at sites undergoing modeling vs. remodeling. Skeletally mature intact beagles, 1-2 years old at the start of the study, were treated daily with clinically relevant doses of alendronate (0.10 or 0.20 mg/kg), risedronate (0.05 or 0.10 mg/kg), raloxifene (0.50 mg/kg), or vehicle (1 mL/kg). Dynamic bone formation parameters were histologically assessed on periosteal, endocortical/trabecular, and intracortical bone envelopes of the rib. Raloxifene significantly increased periosteal surface mineral apposition rate (MAR), a measure of osteoblast activity, compared to all other treatments (+108 to +175%, P < 0.02), while having no significant effect on MAR at either the endocortical/trabecular or intracortical envelope. Alendronate (both 0.10 and 0.20 doses) and risedronate (only the 0.10 dose) significantly (P < or = 0.05) suppressed MAR on the endocortical/trabecular envelope, while none of the bisphosphonate doses significantly altered MAR at either the periosteal or intracortical envelopes compared to vehicle. Based on these results, we conclude that (1) at clinically relevant doses the two classes of antiremodeling agents, bisphosphonates and selective estrogen receptor modulators, exert differential effects on osteoblast activity in the canine rib and (2) this effect depends on whether modeling or remodeling is the predominant mechanism of bone formation.

Alendronate↗

Development of clinical practice guidelines for prevention and treatment of osteoporosis.

Clinical practice guidelines should be written for the physician who sees patients who already have or are at high risk for osteoporosis. They should also guide the physician in distinguishing between those at high and low risk and provide general guidelines for prevention of osteoporosis for the low-risk patient. Patients at high risk may require intervention to prevent further bone loss. The guidelines should be based on the strongest evidence available and be easy to comprehend and apply. Methods to identify individuals at high risk for osteoporosis must be described. Effective interventions also should be described, as should their benefits and risks. Elderly individuals who have a poor diet and little sun exposure may be vitamin D deficient unless a supplement is given. Factors that may be deleterious to the skeleton should be avoided. Weight-bearing exercise is important throughout life. Assessment of fracture risk is important in choosing candidates for intervention, especially interventions aimed at preventing osteoporosis. Measuring bone mass at any skeletal site is the necessary initial step for most individuals; measurement at the hip may best assess the risk of hip fracture. Some risk factors independent of bone mass may also aid in patient selection. The WHO has defined osteoporosis as a bone mass at least 2.5 standard deviations (SDs) below the mean of young normal. Such individuals and those with bone mass from 1 to 2.5 SDs below the mean of young normal may also be considered for intervention. The decision will depend on assessments of the risks, the costs of treatment, the desire of the patient, and the presence of other independent risk factors. The patient with an acute fracture may require an orthopedic intervention and should receive adequate analgesia. Physical therapy is an important adjunct that aids recovery. A number of therapeutic interventions, including adequate calcium intake throughout life and an adequate vitamin D intake, are available to high-risk individuals. These interventions may be recommended generally and do not require a diagnosis of osteoporosis. Similarly, a safe weight-bearing exercise program that helps to maintain muscle strength can be recommended to older patients. Other forms of therapy include hormone replacement, bisphosphonates, and calcitonin. Vitamin D analogs and selective estrogen receptor modulators may be helpful in the future. The risks and costs of each therapy should be weighed against its benefit in slowing bone loss or increasing bone mass and reducing fractures.

Female↗

[Risk of thromboembolism and arteriosclerosis in women].

Young women are at a 3-fold higher risk of experiencing venous thromboembolism compared to young men. This risk is further increased by oral contraceptives, smoking, hereditary thrombophilia and/or low socioeconomic status. There are also hints for gender-specific differences in the arterial system. Coronary heart disease which is particularly important, develops in women 10-15 years later than in men. However, the clinical course in women is often more complicated. In women, thrombophilic predispositions play a more important role before menopause and metabolic risk factors after menopause compared to men. Thrombus formation needs to be initiated by disturbances of at least one element of the Virchow trias. There is principally no difference between men and women. However, all three elements are influenced by estrogen, resulting in gender-specific differences. There is a favorable influence on blood flow by the inhibition of atherogenesis and on the endothelial function by increased NO release, and the unfavorable influence on hemostasis resulting in hypercoagibility. Thus, particularly non-selective hormone replacement therapy for the inhibition of atherogenesis may be questionable due to increased thrombogenicity. The solution may be more selective estrogen receptor modulators. Clinical trials are still needed for both hormone replacement therapy and the therapy of venous and arterial thromboembolism, which have been studied in predominantly male patient cohorts so far.

Adult↗

[The osteoporosis patient with renal insufficiency: what has to be taken into account in the selection and administration of antiosteoporosis medication?].

The incidence of osteoporosis and renal insufficiency increases with age, the use of antiosteoporotic drugs approved for long-term administration in patients with inadequate renal function is therefore a cause for concern. In the dose approved for the treatment of osteoporosis oral bisphosphonates and i.v. ibandronate (3 mg every 12 weeks) have a secure antifracture efficacy, and their use is considered safe in patients with glomerular filtration rate (GFR) > 30 mI/min. Treatment with strontium ranelate and the osteoanabolic substance teriparatide is not altered by impaired renal function until GFR falls below 30 ml/min. Efficiancy of the selective estrogen receptor modulator (SERM) raloxifene is not altered by renal function.

Administration, Oral↗

Effects of hormone replacement therapy on mammographic findings.

To evaluate the effects of different hormone replacement therapy (HRT) protocols on mammographic findings. One-hundred-eighty-two women in menopause were recruited for this prospective study. Breast examination was performed and four basal mammograms were obtained in all cases. Eighty of the cases received HRT by estrogen only; 40 used combined pills of estrogen plus progestagen sequentially; 44 used combined pills of estrogen plus progestagen continuously; 18 used tibolone. Breast examination and mammography were repeated after 11.6+/-2.1 months of HRT. Mammographic parenchymal density was found to be increased in all cases (17.6%). This finding was most prominent in the continuous combined estrogen plus progestagen group (25%) and the lowest in the tibolone group (5.5%). The use of estradiol resulted in more increased density than conjugated estrogen. The increase in the mammographic density is related directly with breast tenderness. Hormone replacement therapy is not contraindicated in the cases of breast disease without atypia. The increase in mammographic density was found to be higher in obese women.

Adult↗

Short-term effects of hormone therapy on serum C-reactive protein levels in postmenopausal women.

OBJECTIVES: The aim of this study was to investigate the effects of tibolone and conjugated equine estrogens (CEEs) plus medroxyprogesterone acetate (MPA) (CEE + MPA) on levels of serum C-reactive protein (CRP), an independent risk factor for cardiovascular disorders, in postmenopausal women. STUDY DESIGN: In this prospective randomized study, we randomly assigned 58 healthy postmenopausal women to CEE (0.625 mg/day) plus MPA (2.5 mg/day) (CEE + MPA) or tibolone (2.5 mg/day). The serum levels of CRP at 3 months after starting treatment were compared with baseline values for both therapies. RESULTS: After 3 months of treatment the median CRP levels increased by 29% in the CEE + MPA group and by 5% in the tibolone group. But, these changes did not have statistical significance (P=0.15, P=0.06, respectively). CONCLUSIONS: Our findings show that neither tibolone nor CEE + MPA caused significant changes in serum CRP levels in postmenopausal women. The potential impact of hormone therapy on serum CRP levels should be investigated in ongoing clinical trials.

C-Reactive Protein↗

Effects of an isopropanolic extract of Cimicifuga racemosa on urinary crosslinks and other parameters of bone quality in an ovariectomized rat model of osteoporosis.

A potential bone-sparing effect of Rhizoma actaeae (= cimicifugae) racemosae (black cohosh) was evaluated in ovariectomized Sprague-Dawley rats. The rats were ovariectomized at 12 weeks of age (body weight, 219-226 g) and placed on a soy-free diet 6 days after surgery. Animals were randomly assigned the following groups: control (n = 10), soy-free diet only; RAL (n = 10), soy-free diet plus raloxifene 3 mg/kg intragastrically; and REM (n = 10), soy-free diet supplemented with an isopropanolic black cohosh extract (Remifemin) with a daily intake of 4500 micro g triterpeneglycosides. Urinary levels of pyridinoline (PYR) and deoxypyridinoline (DPY), specific markers for bone loss, were measured at baseline and at weekly intervals. At the end of the study, the animals were killed and bone loss was determined by volumetric bone mineral density (BMD) measurements and peripheral quantitative computed tomography (pQCT). Mechanical resistance to fracture was also determined. Results demonstrated that an isopropanolic extract of black cohosh significantly diminished the urinary content of PYR and DPY and the morphometric correlates of bone loss associated with ovariectomy in rats. Reversal of the effects of ovariectomy on bone loss began 2-5 weeks after the start of treatment and continued through at least 7 weeks. Results similar in quality and magnitude were obtained in the group treated with raloxifene, a known selective estrogen receptor modulator (SERM). Because extracts of black cohosh are already recognized as safe and effective in the treatment of certain gynecological disorders, a longer-term clinical trial of this herbal remedy for the treatment of osteoporosis is warranted.

2-Propanol↗

Effects of ospemifene and raloxifene on biochemical markers of bone turnover in postmenopausal women.

Ospemifene is a novel selective estrogen receptor modulator (SERM) that is initially being developed for the treatment of vaginal atrophy in postmenopausal women. However, it also shows promise in the prevention and treatment of osteoporosis. As a part of a phase II trial, we compared the effects of ospemifene and raloxifene on bone turnover in postmenopausal women. The study was conducted as a randomized, double-blind study in which 118 healthy postmenopausal women received 30 (n = 29), 60 (n = 30), or 90 mg (n = 30) ospemifene or 60 mg (n = 29) raloxifene for 3 months. Bone resorption was assessed by measuring the urinary outputs of N- and C-terminal cross-linking telopeptides of type I collagen (NTX and CTX, respectively). Bone formation was assessed by measuring bone-specific alkaline phosphatase (bone ALP), osteocalcin (OC), procollagen type I N propeptide (PINP), and procollagen type I C propeptide (PICP) in serum. All markers were studied before and at 3 months and 2-4 weeks after cessation of the medication. Urine NTX outputs decreased in all study groups, and the only statistically significant difference in NTX was observed between raloxifene and 30 mg ospemifene, which was reduced more in the raloxifene group. The output of CTX decreased most clearly in 60- and 90-mg ospemifene groups, but no significant differences between study groups emerged. A significant difference was found between the 90-mg ospemifene group and raloxifene in PINP in favor of ospemifene. No other differences in bone formation markers emerged between ospemifene and raloxifene. The study confirms the bone-restoring activity of ospemifene, which is comparable to that of raloxifene.

Biomarkers↗

Osteoporosis: gender-specific aspects.

Traditionally, osteoporosis has been regarded as a disease of postmenopausal women; nevertheless, although osteoporosis is more common in women than in men, osteoporosis in men is a frequent and a severe condition. Osteoporosis generally can be characterized as either primary or secondary; in men secondary osteoporosis is more frequent than in women. The role of estrogen deficiency in the pathogenesis of postmenopausal osteoporosis is clearly established; remarkably, evidence accumulated over the past years strongly suggests that estrogen also plays the dominant role in regulating the male skeleton. Several independent studies observed decreased serum estradiol levels in men with idiopathic osteoporosis. In contrast to postmenopausal osteoporosis, there are only few studies on the treatment of osteoporosis in men; two different compounds (alendronate and teriparatide) appear to be equally effective in men and women.

Adult↗

Effects of toremifene (TOR) and tamoxifen (TAM) on serum lipids in postmenopausal patients with breast cancer.

This study clarified the difference in the effects on serum lipids between toremifene (TOR) and tamoxifen (TAM). To remove influencing factors, we investigated adjuvant therapy for hormone receptor-positive patients with breast cancer without lymph node metastasis. The subjects were 65 patients who were enrolled in a multicenter randomized comparative study between April 1997 and March 2001. As adjuvant therapy, 20 mg of TAM or 40 mg of TOR was administered for 1 year. The levels of triglyceride (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), apolipoprotein A-1 (Apo A-1), apolipoprotein A(Apo B), and lipoprotein a (Lp(a)) were measured prior to administration and 3, 6, and 12 months after the start of administration. TC, LDL-C, Lp(a) and Apo B significantly decreased from the third month of administration compared with values before the start of administration in both the TOR and TAM groups. HDL-C significantly increased from the third month only in the TOR group. TG significantly increased in the TAM group but significantly decreased in the TOR group in the 12th month of administration. When these two groups were compared, HDL-C was significantly higher (p < 0.01) and TG was significantly lower (p < 0.01) in the TOR group in the 12th month. Improvement of abnormal values of TG, HDL-C and LDL-C was better in the TOR group than in the TAM group after administration for 12 months. The effect on lipid metabolism showed different profiles between the two selective estrogen receptor modulators (SERMs), and TOR gave better results than TAM.

Adult↗

Circulating tumoral cells lack circadian-rhythm in hospitalized metastasic breast cancer patients.

BACKGROUND: The relationship between breast cancer and circadian rhythm variation has been extensively studied. Increased breast tumorigenesis has been reported in melatonin-suppressed experimental models and in observational studies. OBJECTIVES: Circulating Tumor Cells (CTC) circadian- rhythm may optimize the timing of therapies. This is a prospective experimental study to ascertain the day-time and night-time CTC levels in hospitalized metastasic breast cancer (MBC) patients. MATERIAL AND METHODS: CTC are isolated and enumerated from a 08:00 AM and 08:00 PM blood collections. 23 MBC and 23 healthy volunteers entered the study. 69 samples were collected (23 samples at 08:00 AM and 23 samples at 08:00 PM from MBC; 23 samples from healthy volunteers). Results from two patients were rejected due to sample processing errors. No CTC were isolated from healthy-volunteers. RESULTS AND DISCUSSION: No-differences between daytime and night-time CTC were observed. Therefore, we could not ascertain CTC circadian-rhythm in hospitalized metastasic breast cancer patients.

Antineoplastic Agents↗

Tamoxifen improves endothelial function and reduces carotid intima-media thickness in postmenopausal women.

BACKGROUND: Tamoxifen is a selective estrogen-receptor modulator shown to improve several cardiovascular risk factors in postmenopausal women with breast cancer. In animal studies tamoxifen inhibits the progression of atherosclerosis. Although the presence of a history with tamoxifen treatment is related to a lower intima-media thickness (IMT) of the common carotid artery, data from controlled follow-up studies are lacking to support this observation. METHODS: We examined 14 postmenopausal women with early stage breast cancer with indication for tamoxifen treatment (20 mg/d) and 13 healthy postmenopausal women. Flow-mediated dilatation (FMD) of the brachial artery, combined carotid IMT, and aortic pulse wave were measured before and 6 months after treatment in the tamoxifen group and at the same times in the control group. RESULTS: FMD and IMT were significantly increased and decreased, respectively, in the treatment group compared to the control group (FMD: +2.2% +/- 0.9% vs +0.085% +/- 1%, P =.012; IMT: -0.088 +/- 0.03 mm vs +0.04 +/- 0.03 mm, P =.018, mean +/- standard error of the mean, treatment vs control group). These differences remained significant even when adjusted for age, duration of menopause, and cardiovascular risk factors. Low-density lipoprotein cholesterol was also significantly reduced after tamoxifen treatment. CONCLUSIONS: Tamoxifen treatment slows the progression of atherosclerosis in postmenopausal women with breast cancer as assessed by changes in carotid IMT. An improvement in endothelial function and blood lipid profile may be the reason for this beneficial effect.

Aged↗

Effects of tibolone and continuous combined conjugated equine estrogen/medroxyprogesterone acetate on the endometrium and vaginal bleeding: results of the OPAL study.

OBJECTIVES: The primary objective of the Osteoporosis Prevention and Arterial effects of tiboLone study was to compare the effect of tibolone and placebo on the progression of the common carotid artery intima-medial thickness; the common carotid artery intima-medial thickness and bone data will be presented elsewhere. A secondary objective was to assess the effects of tibolone (2.5 mg), continuous combined conjugated equine estrogen/medroxyprogesterone acetate [0.625/2.5 mg], and placebo on the endometrium and vaginal bleeding; these results are the subject of this report. STUDY DESIGN: This 3-year, three-arm, international, randomized, double-blind, parallel group, placebo-controlled clinical trial enrolled 866 postmenopausal women (aged 45-79 years). The endometrium was assessed by annual transvaginal ultrasound scans and end-of-study biopsies (United States/United Kingdom centers only). Vaginal bleeding was recorded in daily diaries. RESULTS: Endometrial thickness measured by transvaginal ultrasound scan increased slightly during the first year with tibolone and conjugated equine estrogen/medroxyprogesterone acetate, without any further progression. After 3 years, there were no significant differences between the tibolone, conjugated equine estrogen/medroxyprogesterone acetate, and placebo groups in the incidence of proliferation (1.4%, 4.8%, and 0%, respectively), endometrial hyperplasia (0% in all groups), or cancer (1, 0, and 1 case, respectively). During the first 3 months, bleeding/spotting rates were greater with conjugated equine estrogen/medroxyprogesterone acetate (48%) than with tibolone (18%; P < .001) or placebo (3%; P < .001). During 3 years of treatment, the incidence of bleeding/spotting was 66%, 48%, and 23% for conjugated equine estrogen/medroxyprogesterone acetate, tibolone, and placebo, respectively. The mean number of bleeding/spotting days was greater in the conjugated equine estrogen/medroxyprogesterone acetate than the tibolone or placebo groups (61, 28, and 7 days, respectively; P = .023 vs tibolone; P < .0001 vs placebo). The mean number of bleeding/spotting episodes was also greater in the conjugated equine estrogen/medroxyprogesterone acetate group (13 episodes) compared with the tibolone group (six episodes; P < .001) and placebo group (four episodes; P < .001). Vaginal bleeding was more commonly reported as an adverse event with conjugated equine estrogen/medroxyprogesterone acetate than tibolone (26.4% vs 10.8%, P < .0001) and as the reason for premature discontinuation (9% vs 2%, P = .001). CONCLUSION: Compared with conjugated equine estrogen/medroxyprogesterone acetate, tibolone has a better tolerability profile with respect to vaginal bleeding but with a similar endometrial safety. These results reinforce the endometrial safety profile of tibolone.

Aged↗

Effect of raloxifene on cardiovascular adverse events in postmenopausal women with osteoporosis.

The impact of selective estrogen receptor modulators on cardiovascular disease outcomes in postmenopausal women remains unclear. This analysis assessed the effect of raloxifene on the incidence of cardiovascular adverse events in postmenopausal women followed for < or =8 years as participants in a 4-year osteoporosis treatment trial and a subsequent 4-year follow-up trial. The Continuing Outcomes Relevant to Evista (CORE) trial, designed to determine the effect of raloxifene on the incidence of invasive breast cancer, was a 4-year follow-up study to the 4-year Multiple Outcomes of Raloxifene Evaluation (MORE) osteoporosis treatment trial. Of the 7,705 participants originally enrolled in MORE, 4,011 were enrolled in CORE and thus participated in both trials (MORE-CORE participants). The incidence of serious cardiovascular (i.e., coronary and cerebrovascular) adverse events during 8 years, confirmed by external adjudication in the 2 trials, was compared between treatment groups using Cox proportional hazards models. The 8-year incidence of serious cardiovascular adverse events did not differ significantly between the raloxifene (5.5%) and placebo (4.7%) groups (hazard ratio [HR] 1.16, 95% confidence interval [CI] 0.86 to 1.56). Similar results were obtained when coronary (HR 1.22, 95% CI 0.82 to 1.83) or cerebrovascular (HR 1.19, 95% CI 0.78 to 1.84) events were analyzed separately, and when cardiovascular events were analyzed in the 459 MORE-CORE participants who were at increased risk of cardiovascular events by previously established criteria (HR 1.03, 95% CI 0.58 to 1.82). In conclusion, we found no evidence of a beneficial or harmful effect of raloxifene on the incidence of cardiovascular events overall, or coronary or cerebrovascular events, in postmenopausal osteoporotic women at relatively low risk of cardiovascular events.

Aged↗

Risk counseling and management in patients with lobular carcinoma in situ.

BACKGROUND: The understanding of lobular carcinoma in situ (LCIS) has evolved since it was first described. LCIS once was thought to be a premalignant condition, but now it is considered a marker for increased risk for developing invasive breast cancer. We evaluated patient perception of risk, counseling, and subsequent management. METHODS: A community cancer registry of 3,605 cases of breast cancer was reviewed. Fifty-five (1.5%) patients with LCIS as their sole diagnosis were identified and these patients were sent a questionnaire. RESULTS: Forty of 55 patients completed the questionnaire for a 73% response rate. The patients' perception of lifetime risk for invasive cancer was variable. Surgeons performed the majority of counseling. Fourteen patients (35%) were placed on a selective estrogen-receptor modulator. Eleven patients (28%) had bilateral mastectomy. Three patients had unilateral mastectomy. Screening recommendations included an annual mammography (64%), a professional examination (64%), and a monthly self-breast examination (75%). CONCLUSION: A patient's perception of risk for invasive breast cancer after a diagnosis of LCIS is widely variable. Patients will adhere to suggested screening recommendations. Surgeons are performing the majority of counseling and must stay abreast on current recommendations.

Adult↗

Vitellogenin synthesis in primary cultures of fish liver cells as endpoint for in vitro screening of the (anti)estrogenic activity of chemical substances.

Concern over possible adverse effects of endocrine-disrupting compounds on fish has caused the development of appropriate testing methods. In vitro screening assays may provide initial information on endocrine activities of a test compound and thereby may direct and optimize subsequent testing. Induction of vitellogenin (VTG) is used as a biomarker of exposure of fish to estrogen-active substances. Since VTG induction can be measured not only in vivo but also in fish hepatocytes in vitro, the use of VTG induction response in isolated fish liver cells has been suggested as in vitro screen for identifying estrogenic-active substances. The main advantages of the hepatocyte VTG assay are considered its ability to detect effects of estrogenic metabolites, since hepatocytes in vitro remain metabolically competent, and its ability to detect both estrogenic and anti-estrogenic effects. In this article, we critically review the current knowledge on the VTG response of cultured fish hepatocytes to (anti)estrogenic substances. In particular, we discuss the sensitivity, specificity, and variability of the VTG hepatocyte assay. In addition, we review the available data on culture factors influencing basal and induced VTG production, the response to natural and synthetic estrogens as well as to xenoestrogens, the detection of indirect estrogens, and the sources of assay variability. The VTG induction in cultured fish hepatocytes is clearly influenced by culture conditions (medium composition, temperature, etc.) and culture system (hepatocyte monolayers, aggregates, liver slices, etc.). The currently available database on estrogen-mediated VTG induction in cultured teleost hepatocytes is too small to support conclusive statements on whether there exist systematic differences of the VTG response between in vitro culture systems, VTG analytical methods or fish species. The VTG hepatocyte assay detects sensitively natural and synthetic estrogens, whereas the response to xenoestrogens appears to be more variable. The detection of weak estrogens can be critical due to the overshadow with cytotoxic concentrations. Moreover, the VTG hepatocyte assay is able to detect antiestrogens as well as indirect estrogens, i.e substances which require metabolic activation to induce an estrogenic response. Nevertheless, more chemicals need to be analysed to corroborate this statement. It will be necessary to establish standardized protocols to minimize assay variability, and to develop a set of pass-fail criteria as well as cut-offs for designating positive and negative responses.

Animals↗