Self-emulsified annatto tocotrienol improves bone histomorphometric parameters in a rat model of oestrogen deficiency through suppression of skeletal sclerostin level and RANKL/OPG ratio.

Menopause is the leading cause of osteoporosis for elderly women due to imbalanced bone remodelling in the absence of oestrogen. The ability of tocotrienol in reversing established bone loss due to oestrogen deficiency remains unclear despite the plenitude of evidence showcasing its preventive effects. This study aimed to investigate the effects of self-emulsified annatto tocotrienol (SEAT) on bone histomorphometry and remodelling in ovariectomised rats. Female Sprague Dawley rats (n=36) were randomly assigned into baseline, sham, ovariectomised (OVX) control, OVX-treated with annatto tocotrienol (AT) (60 mg/kg), SEAT (60 mg/kg) and raloxifene (1 mg/kg). Daily treatment given through oral gavage was started two months after castration. The rats were euthanised after eight weeks of treatment. Blood was collected for bone biomarkers. Femur and lumbar bones were collected for histomorphometry and remodelling markers. The results showed that AT and SEAT improved osteoblast numbers and trabecular mineralisation rate (p<0.05 vs untreated OVX). AT also decreased skeletal sclerostin expression in OVX rats (p<0.05 vs untreated OVX). Similar effects were observed in the raloxifene-treated group. Only SEAT significantly increased bone formation rate and reduced RANKL/OPG ratio (p<0.05 vs untreated OVX). However, no changes in osteoclast-related parameters were observed among the groups (p>0.05). In conclusion, SEAT exerts potential skeletal anabolic properties by increasing bone formation, suppressing sclerostin expression and reducing RANKL/OPG ratio in rats with oestrogen deficiency.

Estradiol treatment attenuates high fat diet-induced microgliosis in ovariectomized rats.

Consumption of a high fat diet (HFD) increases circulating free fatty acids, which can enter the brain and promote a state of microgliosis, as defined by a change in microglia number and/or morphology. Most studies investigating diet-induced microgliosis have been conducted in male rodents despite well-documented sex differences in the neural control of food intake and neuroimmune signaling. This highlights the need to investigate how sex hormones may modulate the behavioral and cellular response to HFD consumption. Estradiol is of particular interest since it exerts a potent anorexigenic effect and has both anti-inflammatory and neuroprotective effects in the brain. As such, the aim of the current study was to investigate whether estradiol attenuates the development of HFD-induced microgliosis in female rats. Estradiol- and vehicle-treated ovariectomized rats were fed either a low-fat chow diet or a 60% HFD for 4 days, after which they were perfused and brain sections were processed via immunohistochemistry for microglia-specific Iba1 protein. Four days of HFD consumption promoted microgliosis, as measured via an increase in the number of microglia in the arcuate nucleus (ARC) of the hypothalamus and nucleus of the solitary tract (NTS), and a decrease in microglial branching in the ARC, NTS, lateral hypothalamus (LH), and ventromedial hypothalamus. Estradiol replacement attenuated the HFD-induced changes in microglia accumulation and morphology in the ARC, LH, and NTS. We conclude that estradiol has protective effects against HFD-induced microgliosis in a region-specific manner in hypothalamic and hindbrain areas implicated in the neural control of food intake.

The synergistic effects of vitamin D and estradiol deficiency on metabolic syndrome in Chinese postmenopausal women.

OBJECTIVE: Recent studies show that vitamin D (VitD) deficiency is associated with metabolic syndrome (MetS). Current evidence suggests that estrogen and VitD have similar physiological functions and potentially interact with bone health. We investigated the association between estradiol (E2) and 25-hydroxyvitamin-D [25(OH)D] with MetS and its components in Chinese postmenopausal women. METHODS: In this cross-sectional study, we examined 616 postmenopausal women (aged 49-86 y) from southern China who were not taking estrogen and VitD/calcium supplements. At the end of data collection, serum E2 and 25(OH)D were measured for each participant. MetS was defined according to the 2006 International Diabetes Federation standard. RESULTS: There was a positive correlation between 25(OH)D and E2. Higher 25(OH)D was associated with a favorable lipid profile, blood pressure, and glucose level. E2 was negatively associated with cholesterol, triglycerides, and blood pressure. The odds ratio for MetS was 2.19 (95% CI, 1.19-4.01, P value for trend=0.009) for deficient compared with sufficient women after multivariable adjustment. This association remained unchanged after further adjusting for E2 levels. After stratified analysis by VitD status, low E2 increased MetS risk in women with VitD deficiency (odds ratio = 3.49, 95% CI, 1.45-8.05 for the lowest vs the highest tertile). CONCLUSIONS: These results suggest a synergistic role of VitD and E2 deficiency in MetS in Chinese postmenopausal women.

[Effects of acupoint catgut embedding combined with auricular point pressure on menopausal syndrome of liver-kidney deficiency type and estradiol].

OBJECTIVE: To observe the efficacy differences between acupoint catgut embedding combined with auricular point pressure with beans and nilestriol on menopausal syndrome of liver-kidney deficiency type, and to explore their effects on estradiol (E2). METHODS: Sixty patients with menopausal syndrome of liver-kidney deficiency type were randomly divided into an acupoint stimulation group and a medication group, 30 cases in each group. The patients in the acupoint stimulation group were treated by acupoint catgut embedding at Taixi (KI 3), Sanyinjiao (SP 6), Shenshu (BL 23), Ganshu (BL 18) and Taichong (LR 3), combined with auricular point pressure at Gan (CO12), Shen (CO10), Neifenmi (CO18), Shenmen (TF4), Pizhixia (AT4); the treatment was given once a week for consecutive four weeks. The patients in the medication group were treated with oral administration of nilestriol, 1 mg, once a day, combined with oral administration of oryzanol, 20 mg, three times per day for consecutive four weeks. The clinical symptom score was compared between the two groups before and after treatment as well as in follow-up visit. The level of E2 was obserced before and after treatment, and the clinical effect was compared. RESULTS: (1) Compared before treatment, the clinical symptom score in the two groups was significantly reduced after treatment and in follow-up visit (all P<0.05); In follow-up visit, the clinical symptom score in the acupoint stimulation group was significantly lower than that in the medication group (P<0.05). The different value before treatment and at follow-up in the acupoint stimulation group was better than that in the medication group (P<0.05). (2) Compared before treatment, the level of E2 in the two groups were increased after treatment (both P<0.05); compared before and after treatment, the difference in the treatment group was significantly higher than that in the medication group (P<0.05). (3) After treatment, the total effective rate was 93.33% (28/30) in the acupoint stimulation group, which was similar to 90.00% (27/30) in the medication group (P>0.05). CONCLUSIONS: Compared with nilestriol, acupoint catgut embedding combined with auricular point pressure with beans could better improve clinical symptoms for patients with menopausal syndrome of liver-kidney deficiency type, and increased the level of E2.

A standardized Humulus lupulus (L.) ethanol extract partially prevents ovariectomy-induced bone loss in the rat without induction of adverse effects in the uterus.

BACKGROUND: Hops (Humulus lupulus (L.)) dietary supplements are of interest as herbal remedies to alleviate menopausal symptoms, such as hot flushes, depression and anxiety. So far, the evidence regarding estrogenic and related properties of hops preparations has been considered insufficient for a market authorization for menopausal indications. PURPOSE: The study aims to investigate a chemically standardized hops extract regarding its safety in the uterus, as wells as its efficacy to prevent bone loss in the ovariectomized rat model. STUDY DESIGN/METHODS: Female Wistar rats were ovariectomized and divided into a control group receiving phytoestrogen-free diet, a group treated with E2benzoate (0.93 mg/kg body weight/d) and a group treated with the standardized hops extract (60 mg/kg body weight/d) for 8 weeks. Micro-computed tomography of the tibiae and vertebrae, as wells as histological changes in the uterus and tibia were analyzed. RESULTS: Neither uterotrophic nor proliferative effects were observed in the endometrium in response to the oral 8-week administration of the hops extract. However, site-dependent skeletal effects were observed. The hops extract significantly decreased the number of osteoclasts in the tibial metaphysis and prevented reduction of the trabecular thickness that resulted from estradiol depletion. In contrast, the hops extract did not prevent the ovariectomy-induced micro-architectural changes in the lumbar vertebra. Certain parameters (e.g. thickness and number of trabeculae) were even found to be below the values determined in the ovariectomized control group. CONCLUSION: Taken together, the results provide evidence for the safety of the standardized hops extract and point to a weak bone type-specific, protective effect on bone loss following estradiol depletion.

[Electroacupuncture improves learning-memory of rats with low estrogen-induced cognitive impairment].

The present study was aimed to investigate the effect of electroacupuncture (EA) on learning-memory of rats with low estrogen-induced cognitive impairment and the possible mechanism. The rat model was established by ovariectomy, which resulted in low estrogen-induced cognitive impairment. EA was applied continuously for 3 months 2 weeks after ovariectomy. Morris water maze was used to test the ability of spatial learning and memory. Enzyme-linked immunosorbent assay (ELISA) and real-time quantitative RT-PCR were used to detect the concentration of serum estradiol (E2) and relative expression of choline acetyltransferase (ChAT) mRNA in hippocampus, respectively. The result showed that, compared with the sham group, the ovariectomy model group exhibited longer escape latency, reduced number of platform-crossing, lower concentration of serum E2, and decreased expression of ChAT mRNA in hippocampus. EA shortened the escape latency and increased the number of platform-crossing in the ovariectomy model group. Moreover, the concentration of serum E2 and the hippocampal expression of ChAT mRNA in the ovariectomy model group were significantly elevated by EA treatment. These results suggest EA is capable of improving learning and memory in ovariectomized rats, and the mechanism involves the up-regulation of the expression of ChAT mRNA in hippocampus induced by the increase of the serum concentration of estrogen.

Estrogen deficiency induces the differentiation of IL-17 secreting Th17 cells: a new candidate in the pathogenesis of osteoporosis.

Th17 cells produce IL-17, and the latter promotes bone loss in collagen-induced arthritis in mice. Blocking IL-17 action in mouse model of rheumatoid arthritis reduces disease symptoms. These observations suggest that Th17 cells may be involved in the pathogenesis of bone loss. However, the role of Th17 cell in estrogen (E2) deficiency-induced bone loss is still not very clear. We investigated the effect of E2 on Th17 differentiation in vivo and IL-17 mediated regulation of osteoclast and osteoblast differentiation. Additionally, effect of IL-17 functional block under E2 deficiency-induced bone loss was studied. In murine bone marrow cells, E2 suppressed IL-17 mediated osteoclast differentiation. IL-17 inhibited formation of mineralized nodules in osteoblasts and this effect was suppressed by E2. E2 treatment to mouse calvarial osteoblasts inhibited the IL-17-induced production of osteoclastogenic cytokines and NF-kB translocation. In ovariectomized mice, there was increase in the number of Th17 cells, transcription factors promoting Th17 cell differentiation and circulating IL-17 levels. These effects were reversed by E2 supplementation. Treatment of neutralizing IL-17 monoclonal antibody to Ovx mice mitigated the E2 deficiency-induced trabecular bone loss and reversed the decreased osteoprotegerin-to-receptor activator of nuclear factor kappa B ligand (RANKL) transcript levels in long bones, increased osteoclast differentiation from the bone marrow precursor cells and decreased osteoblast differentiation from the bone marrow stromal cells. Our findings indicate that E2 deficiency leads to increased differentiation of Th17 cells with attendant up regulation of STAT3, ROR-γt and ROR-α and downregulation of Foxp3 which antagonizes Th17 cell differentiation. Increased IL-17 production in turn induces bone loss by increasing pro-osteoclastogenic cytokines including TNF-α, IL-6 and RANKL from osteoblasts and functional block of IL-17 prevents bone loss. IL-17 thus plays a critical causal role in Ovx-induced bone loss and may be considered a potential therapeutic target in pathogenesis of post menopausal osteoporosis.

Ovarian hormone loss induces bioenergetic deficits and mitochondrial ß-amyloid.

Previously, we demonstrated that reproductive senescence was associated with mitochondrial deficits comparable to those of female triple-transgenic Alzheimer's mice (3xTgAD). Herein, we investigated the impact of chronic ovarian hormone deprivation and 17ß-estradiol (E2) replacement on mitochondrial function in nontransgenic (nonTg) and 3xTgAD female mouse brain. Depletion of ovarian hormones by ovariectomy (OVX) in nontransgenic mice significantly decreased brain bioenergetics, and induced mitochondrial dysfunction and oxidative stress. In 3xTgAD mice, OVX significantly exacerbated mitochondrial dysfunction and induced mitochondrial ß-amyloid and ß-amyloid (Aß)-binding-alcohol-dehydrogenase (ABAD) expression. Treatment with E2 at OVX prevented OVX-induced mitochondrial deficits, sustained mitochondrial bioenergetic function, decreased oxidative stress, and prevented mitochondrial ß-amyloid and ABAD accumulation. In vitro, E2 increased maximal mitochondrial respiration in neurons and basal and maximal respiration in glia. Collectively, these data demonstrate that ovarian hormone loss induced a mitochondrial phenotype comparable to a transgenic female model of Alzheimer's disease (AD), which was prevented by E2. These findings provide a plausible mechanism for increased risk of Alzheimer's disease in premenopausally oophorectomized women while also suggesting a therapeutic strategy for prevention.

Improvement of bone strength and dermal thickness due to dietary edible bird's nest extract in ovariectomized rats.

Oral administration of edible bird's nest extract (EBNE) improved bone strength and calcium concentration in the femur of ovariectomized rats. Dermal thickness was also increased by EBNE supplementation, whereas EBNE administration did not affect the serum estradiol concentration. These results suggest that EBNE is effective for the improvement of bone loss and skin aging in postmenopause all women.

Bone mineral density loss during adjuvant chemotherapy in pre-menopausal women with early breast cancer: is it dependent on oestrogen deficiency?

Pre-menopausal women given adjuvant chemotherapy for breast cancer experience both premature ovarian failure and loss of bone mineral density (BMD), and this study was designed to see if these observations are causally linked. Chemotherapy was administered to 41 pre-menopausal women with early breast cancer enrolled prospectively in a study of ovarian function and BMD in such women given systemic therapy. After giving written informed consent, all patients underwent baseline and regular on-treatment measurements of BMD by dual-energy X-ray absorptiometry (DXA) scan, bone turnover and ovarian function by analysis of serum hormone levels and self-reported menstrual diaries. Baseline lumbar spine BMD in the 41 women given chemotherapy was higher than the normal population (Z score 0.28 ± 0.14 (mean ± SEM), P = 0.047), and fell significantly over the first 6 months from a mean of 1.05-1.01 g/m(2), P < 0.0001, and similar but smaller changes were demonstrated in hip BMD. This fall was independent of age at diagnosis, type of chemotherapy, development of amenorrhoea or either baseline or on-treatment estradiol concentration. During the 6 months after completion of adjuvant chemotherapy, BMD fell further only in those women with low estradiol or experiencing amenorrhoea during the first 6 months, although all groups showed evidence of increased bone turnover. This study demonstrates loss of both spine and hip BMD in pre-menopausal women during 6 months' adjuvant systemic chemotherapy to be independent of changes in ovarian function. Ovarian function was, however, related to BMD changes after chemotherapy ceased.

Soy isoflavones prevent the ovarian hormone deficiency-associated rise in leukocytes in rats.

Recent reports indicate that ovariectomy (ovx) increases lymphopoiesis. Ipriflavone, a synthetic isoflavone, has been reported to reduce lymphocytes in postmenopausal women. The aim of this study was to investigate whether naturally occurring isoflavones also affect lymphopoiesis in ovarian hormone deficiency. The present study was carried out using an ovariectomized (ovx) rat model. To mimic early menopause, forty-eight 12-month-old Sprague-Dawley rats were either sham-operated (sham; 1 group) or ovx (3 groups) and were fed a standard semi-purified diet for 120 days. Thereafter, the ovx groups received one of the three doses of isoflavones: 0 (ovx), 500 (ISO500), or 1000 (ISO1000) mg/kg diet for 100 days. Ovariectomy increased total leukocyte counts significantly (p < 0.05) as a result of increased (p < 0.05) lymphocyte, monocyte, eosinophil, and basophil differential counts. Isoflavones at 500 and 1000 mg/kg diet returned the total leukocyte counts, as well as leukocyte subpopulations, to levels comparable to that of sham-operated rats. No other hematological parameters, e.g., red blood cell counts or red cell indices, were affected by ovariectomy or isoflavones. We conclude that soy isoflavones restore normal leukocyte counts elevated in ovarian hormone deficiency.

Estrogen depletion differentially affects blood pressure depending on age in Long-Evans rats.

Normotensive female rats exhibit age-related decreases in estrous cyclicity and increases in blood pressure. In spontaneously hypertensive rats, estrogens, including dietary phytoestrogens, prevent or attenuate the increased blood pressure associated with estrogen depletion. The present studies examine the effects of ovariectomy (OVX) at either 3 or 10 mo of age. Although blood pressure increases from 3 to 9 mo, OVX at 3 mo of age has no added effect--despite the fact that OVX (compared to ovary-intact) rats weighed significantly more. In contrast, aging from 10 to 16 mo is associated with a further increase in blood pressure, which is potentiated by estrogen depletion. Removal of dietary phytoestrogens exacerbated the hypertensive effects of OVX in these middle-aged rats. As in younger rats, estrogen depletion at 10 mo of age was associated with greater weight gain. Whereas estrogen depletion at 3 mo of age was without effect on fluid intake over the next 6 mo, OVX at 10 mo of age was associated with decreased fluid intake. In a final study, rats were OVX at 3 mo of age with estradiol (E2) treatment initiated at 10 mo of age. Long-term OVX ( >10 mo) was associated with increased blood pressure and mortality at 14-16 mo of age. Circulating levels of E2 were decreased by OVX. Plasma aldosterone was increased by OVX, an effect which was prevented by either E2 or phytoestrogens. Neither E2 nor aldosterone was affected by age. These data indicate that (a) the physiological effects of estrogen depletion vary with age; (b) phytoestrogens in the diet exert some protective effects; and (c) long-term OVX in the absence of hormone re-placement is associated with premature mortality. We suggest that chronic increases in aldosterone and sympathetic tone underlie the hypertensive effects of estrogen depletion.

Dehydroepiandrosterone restores hepatocellular function and prevents liver damage in estrogen-deficient females following trauma and hemorrhage.

INTRODUCTION: Recent studies have shown that administration of the sex steroid dehydroepiandrosterone (DHEA) in males following trauma-hemorrhagic shock has salutary effects on the depressed cardiovascular and immunological functions under those conditions. Since the effects of sex steroids are gender specific, we examined whether administration of DHEA has any beneficial effects on hepatocellular function in female rats with low estrogen levels following trauma-hemorrhage. METHODS: Ovariectomy was performed in female Sprague-Dawley rats 14 days prior to the experiments. The animals then underwent a 5-cm midline laparotomy and were subjected to hemorrhagic shock (40 mm Hg for 90 min). This was followed by fluid resuscitation (Ringer's lactate over 60 min) and administration of DHEA (30 mg/kg BW) or vehicle subcutaneously at the end of resuscitation. At 24 h after resuscitation hepatocellular function, i.e., clearance of indocyanine green (ICG), and hepatocyte damage (serum alanine aminotransferase) were measured. Plasma levels of DHEA and 17beta-estradiol were also assayed. RESULTS: Vehicle-treated rats had significantly reduced hepatocellular function, increased ALT activity, and decreased levels of 17beta-estradiol following trauma-hemorrhage compared to sham-operated animals (P < 0.05, ANOVA and Student-Newman-Keuls test). In animals receiving DHEA following trauma-hemorrhage, hepatocellular function and ALT activity were similar to those of shams. However, administration of DHEA did not influence the plasma levels of 17beta-estradiol. CONCLUSIONS: Administration of DHEA following trauma-hemorrhage restored hepatocellular function and reduced hepatic damage that was observed in ovariectomized female rats under such conditions. This salutary effect of DHEA did not appear to be due to elevated levels of plasma 17beta-estradiol. We therefore propose that DHEA should be considered a novel, safe, and useful adjunct in the treatment of trauma-induced hepatocellular dysfunction in ovariectomized and postmenopausal females.

Role of soy protein with normal or reduced isoflavone content in reversing bone loss induced by ovarian hormone deficiency in rats.

Soy protein, a rich source of isoflavones, fed immediately after an ovariectomy prevents bone loss in rats. Reports of the effectiveness of natural and synthetic isoflavones in preventing or treating osteoporosis led us to examine the effect of soy protein in reversing established bone loss. Seventy-two 95-d-old female Sprague-Dawley rats were assigned to 6 groups. The rats were either sham operated (SHAM; 2 groups) or ovariectomized (OVX; 4 groups) and then fed a casein-based, semipurified diet. Thirty-five days after surgery, 1 SHAM and 1 OVX group were killed to examine the occurrence of bone loss. Thereafter, the other SHAM and 1 OVX groups continued to receive the casein-based diet. Whereas the remaining 2 OVX groups received diets in which casein was replaced by soy protein with normal (OVX+SOY) or reduced (OVX+SOY-) isoflavone content for 65 days. The OVX control group had significantly lower femoral and fourth lumbar vertebral bone densities than the SHAM group. Femoral density of rats fed SOY or SOY- diets were not significantly different from SHAM or OVX controls. This suggests a slight reversal of cortical bone loss that may be partially due to higher femoral insulin-like growth factor I mRNA transcripts resulting from both the SOY and SOY- diets. The ovariectomy-induced increases in indexes of bone turnover were not ameliorated by either of the soy diets, suggesting that any positive effect of soy was achieved through enhanced bone formation rather than slowed bone resorption. Long-term consumption of soy or its isoflavones may be needed to produce small but continued increments in bone mass.

Cerebral vasodilating capacity during forebrain ischemia: effects of chronic estrogen depletion and repletion and the role of neuronal nitric oxide synthase.

The effects of chronic 17beta-estradiol (E2) depletion, via ovariectomy (OVX), and its repletion, on cortical cerebral blood flow (CBF) and EEG activities during forebrain ischemia, as well as post-ischemic recovery and neuropathology, were assessed and compared with results obtained in normal female rats. We also examined whether neuronal nitric oxide synthase (nNOS) activity is affected by OVX and E2 replacement and whether NOS-derived NO supports vasodilation during ischemia. OVX females displayed a significantly lower CBF during ischemia (10% of baseline) than did normal females (23% of baseline). In OVX rats, given chronic low-dose E2 treatment (0.1 mg kg(-1) day(-1)), intra-ischemic CBF was similar to normal females (25% of baseline). However, at supraphysiologic E2 doses (> or = 0.5 mg kg(-1) day(-1)), that benefit was diminished or lost. Intra-ischemic EEG power reductions and post-ischemic survival rates, neurological dysfunction, and histopathology displayed similar relative differences among groups as the CBF findings. Intra-ischemic CBF was reduced by nNOS inhibition, with ARL 17477, in normal and low-dose E2-treated OVX rats (4-8% baseline). The repressed intra-ischemic vasodilating function in OVX rats may be due to reductions in nNOS activity, because untreated OVX rats showed a 50% lower cortical nNOS activity than that in normal rats and in rats treated with low or high dose (5 mg kg(-1) day(-1)) E2. However, the inability to restore vasodilating function despite normalization of nNOS activity indicates that another mechanism is responsible for the repression of vasodilatory function in the high-dose group. These findings suggest that E2, at levels within the physiological range, promotes ischemic neuroprotection via improving vasodilating capacity. One possible mechanism may relate to E2 enhancing brain nNOS expression and activity.

Effects of growth hormone and low dose estrogen on bone growth and turnover in long bones of hypophysectomized rats.

Pituitary hormones are recognized as critical to longitudinal growth, but their role in the radial growth of bone and in maintaining cancellous bone balance are less clear. This investigation examines the histomorphometric effects of hypophysectomy (Hx) and ovariectomy (OVX) and the subsequent replacement of growth hormone (GH) and estrogen (E), in order to determine the effects and possible interactions between these two hormones on cortical and cancellous bone growth and turnover. The replacement of estrogen is of interest since Hx results in both pituitary and gonadal hormone insufficiencies, with the latter being caused by the Hx-associated reduction in follicle stimulating hormone (FSH). All hypophysectomized animals received daily supplements of hydrocortisone (500 microg/kg) and L-thyroxine (10 microg/kg), whereas intact animals received daily saline injections. One week following surgery, hypophysectomized animals received either daily injections of low-dose 17 beta-estradiol (4.8 microg/kg s.c.), 3 X/d recombinant human GH (2 U/kg s.c.), both, or saline for a period of two weeks. Flurochromes were administered at weekly intervals to label bone matrix undergoing mineralization. Whereas Hx resulted in reductions in body weight, uterine weight, and tibial length, OVX significantly increased body weight and tibial length, while reducing uterine weight. The combination of OVX and Hx resulted in values similar to Hx alone. Treatment with GH normalized body weight and bone length, while not affecting uterine weight in hypophysectomized animals. Estrogen increased uterine weight, while not impacting longitudinal bone growth and reduced body weight. Hypophysectomy diminished tibial cortical bone area through reductions in both mineral appositional rate (MAR) and bone formation rate (BFR). While E had no effect, GH increased both MAR and BFR, though not to sham-operated (control) levels. Hypophysectomy reduced proximal tibial trabecular number and cancellous bone area, and increased trabecular separation. Both GH and E reduced cancellous osteopenia, although employing different mechanisms. GH reduced the decrease in trabecular thickness, whereas E reduced the decrease in trabecular number and the increase in trabecular separation. Hypophysectomy reduced both Tb.MAR and Tb.BFR while treatment with GH enhanced them. This investigation has shown that Hx and GH have a dramatic impact on selected static and dynamic indices of rat cortical and cancellous histomorphometry. Furthermore, the mechanisms of action of GH and E differ, and suggest that some of the skeletal changes associated with Hx are caused by deficiencies in estrogen as well as deficiencies in growth hormone.

Estrogen replacement therapy.

The popularity of estrogen therapy for the menopausal woman seems to be on the rise again, with new evidence on the risks and treatment of osteoporosis and the protective effect of progestin on the endometrium becoming clearer. The risks of estrogen treatment must remain a prime concern of the practitioner, and hazards may be minimized through careful patient selection, education, examination, treatment, and follow-up. The resurgence of interest in the plight of the menopausal woman has stimulated an increasing number of competent investigators to attempt to solve the mysteries that until recently have been evaluated and treated by anecdote and homeopathic ministrations.