Vascular resistance of central retinal artery is reduced in postmenopausal women after use of estrogen

Association between blood urea nitrogen levels and diabetic retinopathy in diabetic adults in the United States (NHANES 2005-2018)

Objective

To investigate the association between blood urea nitrogen (BUN) levels and diabetic retinopathy (DR) in adults with diabetes mellitus (DM).

Methods

Seven cycles of cross-sectional population information acquired from NHANES(national health and nutrition examination surveys) 2005-2018 were collected, from which a sample of diabetic adults was screened and separated into two groups based on whether or not they had DR, followed by weighted multivariate regression analysis. This study collected a complete set of demographic, biological, and sociological risk factor indicators for DR. Demographic risk factors comprised age, gender, and ethnicity, while biological risk factors included blood count, blood pressure, BMI, waist circumference, and glycated hemoglobin. Sociological risk factors included education level, deprivation index, smoking status, and alcohol consumption.

Results

The multiple regression model revealed a significant connection between BUN levels and DR [odds ratio =1.04, 95% confidence interval (1.03-1.05), p-value <0.0001],accounting for numerous variables. After equating BUN levels into four groups, multiple regression modeling showed the highest quartile (BUN>20 mg/dl) was 2.22 times more likely to develop DR than the lowest quartile [odds ratio =2.22, 95% confidence interval (1.69-2.93), p- value <0.0001]. Subgroup analyses revealed that gender, race, diabetes subtype, and duration of diabetes had a regulating effect on the relationship between BUN and DR.

Conclusion

BUN levels were related with an increased prevalence of DR, particularly in individuals with BUN >20 mg/dl. These findings highlight the significance of BUN level in assessing the risk of DR.

Age- and sex-related differences in the retinal capillary plexus in healthy Chinese adults

BACKGROUND

To assess age- and sex-related changes in the superficial retinal capillary plexus (SCP) and deep retinal capillary plexus (DCP) in healthy Chinese adults.

METHODS

In this cross-sectional study, all data were derived from the community-based Jidong Eye Cohort Study. Participants underwent optical coherence tomography angiography (OCTA) and other ocular and systemic examinations. The vessel densities of the whole measured area, parafovea, and four quadrants in the SCP and DCP were measured.

RESULTS

We recruited 1036 eyes of 1036 healthy participants; the mean age was 40.4 ± 9.8 years, and 449 (43.3%) participants were males. The SCP and DCP vessel densities in all regions, except for temporal and nasal regions in the SCP, non-linearly decreased with age. The DCP vessel densities began to decrease at approximately 35 years of age, while the SCP vessel densities began to decrease at approximately 40 years of age. The DCP vessel densities decreased more rapidly than the SCP vessel densities at 35-50 years of age. The DCP vessel densities remained stable or slightly decreased after the age of 50 years in females, while those decreased linearly in most regions in males.

CONCLUSIONS

The retinal vessel density decreased earlier and more rapidly in the DCP than in the SCP, and the effect of aging on the DCP vessel density was sex-dependent. Our findings suggest that age and sex should be considered when interpreting clinical quantitative OCTA data.

Functional optical coherence tomography at altitude: retinal microvascular perfusion and retinal thickness at 3,800 meters

Cerebral hypoxia is a serious consequence of several cardiorespiratory illnesses. Measuring the retinal microvasculature at high altitude provides a surrogate for cerebral microvasculature, offering potential insight into cerebral hypoxia in critical illness. Additionally, while sex-specific differences in cardiovascular diseases are strongly supported, few have focused on differences in ocular blood flow. We evaluated the retinal microvasculature in males (n=11) and females (n=7) using functional optical coherence tomography at baseline (1,130m) (Day 0), following rapid ascent (Day 2) and prolonged exposure (Day 9) to high altitude (3,800m). Retinal vascular perfusion density (rVPD; an index of total blood supply), retinal thickness (RT; reflecting vascular and neural tissue volume) and arterial blood were acquired. As a group, rVPD increased on Day 2 vs. Day 0 (p<0.001) and was inversely related to PaO₂ (R²=0.45; p=0.006). By Day 9, rVPD recovered to baseline, but was significantly lower in males vs. females (p=0.007). RT was not different on Day 2 vs. Day 0 (p>0.99) but was reduced by Day 9 relative to Day 0 and Day 2 (p<0.001). RT changes relative to Day 0 were inversely related to changes in PaO₂ on Day 2 (R²=0.6; p=0.001) and Day 9 (R²=0.4; p=0.02). RT did not differ between sexes. These data suggest differential time course and regulation of the retina during rapid ascent and prolonged exposure to high altitude and are the first to demonstrate sex-specific differences in rVPD at high altitude. The ability to assess intact microvasculature contiguous with the brain has widespread research and clinical applications.

Sex Hormones and Their Effects on Ocular Disorders and Pathophysiology: Current Aspects and Our Experience

Sex hormones are molecules produced by the gonads and to a small extent by the adrenal gland, which not only determine the primary and secondary sexual characteristics of an individual, differentiating man from woman, but also participate in the functioning of the various systems of the body. The evidence that many eye diseases differ in terms of prevalence between men and women has allowed us, in recent years, to carry out several studies that have investigated the association between sex hormones and the pathophysiology of eye tissues. Specific receptors for sex hormones have been found on the lacrimal and meibomian glands, conjunctiva, cornea, lens, retina, and choroid. This work summarizes the current knowledge on the role that sex hormones play in the pathogenesis of the most common ocular disorders and indicates our clinical experience in these situations. The aim is to stimulate an interdisciplinary approach between endocrinology, neurology, molecular biology, and ophthalmology to improve the management of these diseases and to lay the foundations for new therapeutic strategies.

Does exogenous androgen use affect the retinal blood flow: An OCTA study in transgender men

PURPOSE

This study aims to investigate the effect of using exogenous androgen on retinal microvascular structures in transgender men.

METHODS

Retinal microvascular structures of transgender men and healthy women in the control group were visualized with optical coherence tomography angiography (OCTA). Foveal avascular zone (FAZ), superficial capillary vascular density (sCVD), deep capillary vascular density (dCVD), and radial peripapillary capillary (RPC) vascular density were evaluated.

RESULTS

Thirty transgender men and 30 healthy women were included in the study. There were no significant differences between transgender men and the control group in terms of FAZ, central macular thickness, parafoveal, and perifoveal retinal thicknesses (p = 0.859, 0.288, 0.561, and 0.719; respectively). sCVD were found to be low in transgender men in the whole image, parafoveal, and perifoveal zones (p = 0.006, 0.025, and 0.005; respectively). Although there were low values of dCVD of the whole image, parafoveal, and perifoveal zones in transgender men, the difference was not statistically significant (p = 0.295, 0.085, and 0.270; respectively). RPC vessel densities in the whole image, peripapillary zone, and the inferior of the optic disc were found to be significantly low in transgender men (p = 0.003, 0.005, and 0.003; respectively).

CONCLUSION

In this study, a decrease in vessel density in the superficial retinal layers and around the optic disc was detected in transgender men. These findings suggest that routine ophthalmological examination may be important in individuals who use exogenous androgens.

Girl Power in Glaucoma: The Role of Estrogen in Primary Open Angle Glaucoma

Estrogen is essential in maintaining various physiological features in women, and a decline in estrogen levels are known to give rise to numerous unfortunate symptoms associated with menopause. To alleviate these symptoms hormone replacement therapy with estrogen is often used, and has been shown to be fruitful in improving quality of life in women suffering from postmenopausal discomforts. An often forgotten condition associated with menopause is the optic nerve disorder, glaucoma. Thus, estrogen may also have an impact in maintaining the retinal ganglion cells (RGCs), which make up the optic nerve, thereby preventing glaucomatous neurodegeneration. This review aims to provide an overview of possible associations of estrogen and the glaucoma subtype, primary open-angle glaucoma (POAG), by evaluating the current literature through a PubMed-based literature search. Multiple in vitro and in vivo studies of RGC protection, as well as clinical and epidemiological data concerning the well-defined retinal neurodegenerative disorder POAG have been reviewed. Over all, deficiencies in retinal estrogen may potentially instigate RGC loss, visual disability, and eventual blindness. Estrogen replacement therapy may therefore be a beneficial future treatment. However, more studies are needed to confirm the relevance of estrogen in glaucoma prevention.

Gender-related Influences on Superficial Papillary Microcirculation Measured with Optical Coherence Tomography Angiography in Patients with Glaucoma

Purpose: To evaluate the optic nerve head (ONH), macular vessel density, and retinal nerve fiber layer (RNFL) thickness differences between the genders. Material and methods: In this prospective case-control cross-sectional study 111 healthy subjects and 130 primary open-angle glaucoma (OAG) patients were examined with optical coherence tomography angiography (OCT-A (RS-3000 Advance (Nidek, Gamagori, Japan))). The vessel density in the peripapillary and macular area as well as the RNFL thickness was evaluated. Results: Men appeared to have less RNFL thickness compared with women in early glaucomatous group, being significant at the whole circumpapillary retinal nerve fiber layer (cpRNFL) thickness and inferior and nasal quadrants: (cpRNFL) (71.01 ± 9.32 vs 77.64 ± 9.95 μm; P = .001), superior quadrant (89.10 ± 16.63 vs 92.97 ± 17.53 μm; P = .284), inferior quadrant (83.03 ± 19.17 vs 95.07 ± 21.70 μm; P = .006), temporal quadrant (57.11 ± 10.36 vs 61.78 ± 11.37 μm; P = .043), nasal quadrant (54.81 ± 11.42 vs 60.73 ± 11.62 μm; P = .016). Circumpapillary (wcpVD) and macular (wmVD) vessel density values were lower in men than women in the early stage OAG group, being wmVD significantly lower: wcpVD (15.53 ± 2.45% vs 16.81 ± 3.17%, P = .032) and wmVD values (12.51 ± 2.21 vs 13.63 ± 2.28%, P = .019), but not in the moderate OAG group (wcpVD 14.46 ± 2.20% vs 16.61 ± 3.10%, P = .056 and wmVD 12.61 ± 2.40% vs 12.74 ± 2.54%, P = .870). There were no significant differences between men and women for RNFL thickness and the vessel density parameters in normal group. Conclusion: Both, the thickness of the nerve fiber layer and peripapillary and macular vessel density are lower in men than in women with glaucoma, more markedly in early stage glaucomatous patients.

Effects of Sex Hormones on Ocular Blood Flow and Intraocular Pressure in Primary Open-angle Glaucoma: A Review

Primary open-angle glaucoma (POAG) is a multifactorial optic neuropathy characterized by progressive retinal ganglion cell death and visual field loss. Some speculate that sex plays a role in the risk of developing POAG and that the physiological differences between men and women may be attributed to the variable effects of sex hormones on intraocular pressure, ocular blood flow, and/or neuroprotection. Estrogen, in the form of premenopausal status, pregnancy, and postmenopausal hormone therapy is associated with an increase in ocular blood flow, decrease in intraocular pressure and neuroprotective properties. The vasodilation caused by estrogen and its effects on aqueous humor outflow may contribute. In contrast, although testosterone may have known effects in the cardiovascular and cerebrovascular systems, there is no consensus as to its effects in ocular health or POAG. With a better understanding of sex hormones in POAG, sex hormone-derived preventative and therapeutic considerations in disease management may provide for improved sex-specific patient care.

Sex Hormones and Optic Nerve Disorders: A Review

Aim: This review article presents a comprehensive overview of the literature on sex hormones (estrogens, androgens, progesterone) and optic nerve disorders, with a discussion of the implications for therapy and prevention.

Methods: Epidemiological, pre-clinical and clinical studies were reviewed.

Results: Analysis of the biological basis for a relationship between eye diseases and sex hormones showed that some types of hormones can exert a protective effect either directly on the retina and optic nerve or indirectly by modulating ocular blood flow. For example, it seems that estrogen exposure has a protective effect against glaucoma, whereas its deficit may lead to early onset of the disease. If further studies confirm the data in the literature, estrogen therapy, because of its antioxidant action, may be effective in the treatment of Leber's hereditary optic neuropathy, whereas, in the light of current studies, there does not seem to be an influence of estrogen on non-arteritic anterior ischemic optic neuritis (NAION).

Conclusions: Although there is some evidence that in some optic nerve pathologies the sex hormones seem to play an important role there are still too few studies providing evidence for its wider use in clinical practice.

Gonadal Hormones and Retinal Disorders: A Review

AIM

Gonadal hormones are essential for reproductive function, but can act on neural and other organ systems, and are probably the cause of the large majority of known sex differences in function and disease. The aim of this review is to provide evidence for this hypothesis in relation to eye disorders and to retinopathies in particular.

METHODS

Epidemiological studies and research articles were reviewed.

RESULTS

Analysis of the biological basis for a relationship between eye diseases and hormones showed that estrogen, androgen, and progesterone receptors are present throughout the eye and that these steroids are locally produced in ocular tissues. Sex hormones can have a neuroprotective action on the retina and modulate ocular blood flow. There are differences between the male and the female retina; moreover, sex hormones can influence the development (or not) of certain disorders. For example, exposure to endogenous estrogens, depending on age at menarche and menopause and number of pregnancies, and exposure to exogenous estrogens, as in hormone replacement therapy and use of oral contraceptives, appear to protect against age-related macular degeneration (both drusenoid and neurovascular types), whereas exogenous testosterone therapy is a risk factor for central serous chorioretinopathy. Macular hole is more common among women than men, particularly in postmenopausal women probably owing to the sudden drop in estrogen production in later middle age. Progestin therapy appears to ameliorate the course of retinitis pigmentosa. Diabetic retinopathy, a complication of diabetes, may be more common among men than women.

CONCLUSION

We observed a correlation between many retinopathies and sex, probably as a result of the protective effect some gonadal hormones may exert against the development of certain disorders. This may have ramifications for the use of hormone therapy in the treatment of eye disease and of retinal disorders in particular.

Investigation of causes of sex-related differences in ocular blood flow in healthy eyes determined by laser speckle flowgraphy

Sex-related differences are present in the systemic and ocular blood flow. However, the cause of the sex-related differences has not been determined. We investigated the ocular blood flow, represented by the mean blur rate (MBR), on the optic nerve head (ONH) determined by laser speckle flowgraphy in 138 males (63.9 ± 8.9 years) and 194 females (63.5 ± 9.4 years). The correlations between the MBR on the ONH and the clinical data were determined. The overall ONH-MBR was significantly higher in females than males (P < 0.001). In addition, the levels of the hemoglobin and hematocrit were significantly lower in females than in males (P < 0.001). The ONH-MBR was negatively and significantly correlated with the levels of the hemoglobin and hematocrit (both, P < 0.001). Multiple regression analyses showed that the sex (β = 0.248, P < 0.001) was an independent factor correlated with the ONH-MBR when the clinical examination data were not included in the analyses. However, when the clinical examination data were included, the hemoglobin level (β = −0.295, P < 0.001) was an independent factor that contributed to the ONH-MBR but the sex was not. We conclude that the sex-related differences in the hemoglobin level and the negative correlation between hemoglobin and the ONH-MBR are the causes of the sex-related differences in the ONH-MBR.

Transient Monocular Vision Loss on Awakening: A Benign Amaurotic Phenomenon

BACKGROUND

Transient monocular vision loss (TMVL) is an alarming symptom owing to potentially serious etiologies such as thromboembolism or giant cell arteritis. Our objective is to describe the phenomenon of TMVL present on awakening, which may represent a distinct and benign entity.

METHODS

We performed a retrospective observational case series of 29 patients who experienced TMVL on awakening. Patients who described monocular dimming or blackout of vision were included, and those with blurred vision, concurrent eye pain, and binocular vision loss were excluded. Descriptive statistics were used to summarize the study population.

RESULTS

Of the 29 patients we studied, 90% (n = 26) were female and 48% had crowded discs (cup-to-disc ratio ≤0.2). The mean age was 45.4 years, although women were significantly younger than men (mean ages 43.4 and 62.7 years, respectively, P = 0.017). Brain magnetic resonance imaging and vascular imaging (magnetic resonance angiography, computed tomographic angiography, or carotid Doppler) were performed in 69% and 55% of cases, respectively, and were uniformly negative. In 14 patients for whom clear follow-up data could be obtained, no medically or visually significant sequelae of this syndrome were found, and 50% experienced resolution of symptoms.

CONCLUSIONS

Evaluation was uniformly negative when patients described waking with isolated vision loss in 1 eye with subsequent resolution, usually in less than 15 minutes. The natural history seems benign with symptoms frequently remitting spontaneously. This visual phenomenon may represent an autoregulatory failure resulting in a supply/demand mismatch during low-light conditions.

Effect of short-term estrogen therapy on endothelial function: a double-blinded, randomized, controlled trial

OBJECTIVE

To evaluate the effect of short-term hormone replacement therapy with 0.625 mg conjugated estrogens daily on endothelial function of healthy postmenopausal women, using flow-mediated dilation (FMD) of the brachial artery.

METHODS

We performed a double-blinded, randomized, controlled trial over 3 years. Randomization was performed using computer-generated sorting. All participants were blinded to the use of conjugated equine estrogens (CEE) or placebo and FMD was assessed by a blinded examiner, before and after 28 days of medication. A total of 64 healthy postmenopausal women were selected and randomly assigned into two groups of treatment: 0.625 mg of CEE or placebo.

RESULTS

FMD values were statistically different between the groups (p = 0.025): the group receiving CEE showed a FMD value of 0.011 compared to the placebo group (FMD = -0.082). The two groups were additionally evaluated for homogeneity through the Shapiro-Wilk test in respect to variables that could interfere with endothelial function such as age (p = 0.729), body mass index (p = 0.891), and time since menopause (p = 0.724). Other variables were excluded during selection of the participants such as chronic vascular conditions, smoking, and sedentary lifestyle.

CONCLUSION

Our results demonstrate that the administration of 0.625 mg CEE for 28 days is effective in improving vascular nitric oxide-dependent dilation assessed by FMD of the brachial artery in postmenopausal women.

CLINICAL TRIAL REGISTRATION

NCT01482416.

Association of bone mineral density and diabetic retinopathy in diabetic subjects: the 2008-2011 Korea National Health and Nutrition Examination Survey

Because diabetic retinopathy increases fracture risk, we studied the association between bone mineral density (BMD) and diabetic retinopathy in a nationally representative sample. A significant association between the presence of diabetic retinopathy and low BMD was observed. Therefore, diabetic retinopathy might be considered as a marker of low BMD.

INTRODUCTION

Several diabetic complications, including nephropathy, retinopathy, and peripheral neuropathy, are associated with a higher fracture risk in diabetic subjects. However, in contrast to diabetic nephropathy and peripheral neuropathy, which are associated with low bone mineral density (BMD), little is known about the association between BMD and diabetic retinopathy. The aim of the present study was to determine whether the prevalence of diabetic retinopathy is associated with BMD.

METHODS

This cross-sectional study included a nationally representative sample consisting of 4357 men aged 50 years and older and 4392 postmenopausal women who participated in the Korea National Health and Nutritional Examination Survey (KNHANES) from 2008 to 2011 and underwent BMD measurement by dual-energy X-ray absorptiometry (DXA) and diabetic retinopathy assessments using seven standard gradable photographs.

RESULTS

The diabetic women with retinopathy had lower mean BMD at all measured sites than those without retinopathy, although the BMD difference between the two groups was small (3-5 %). In addition, the diabetic women with retinopathy were 2.27 times more likely to have osteoporosis following adjustments for all clinically relevant covariates. However, the prevalence of diabetes mellitus (DM) or diabetic retinopathy was not associated with the prevalence of osteoporosis in men.

CONCLUSIONS

This study has shown that the presence of diabetic retinopathy is significantly associated with a reduced BMD and increased prevalence of osteoporosis in diabetic women.

Gender differences in ocular blood flow

Gender medicine has been a major focus of research in recent years. The present review focuses on gender differences in the epidemiology of the most frequent ocular diseases that have been found to be associated with impaired ocular blood flow, such as age-related macular degeneration, glaucoma and diabetic retinopathy. Data have accumulated indicating that hormones have an important role in these diseases, since there are major differences in the prevalence and incidence between men and pre- and post-menopausal women. Whether this is related to vascular factors is, however, not entirely clear. Interestingly, the current knowledge about differences in ocular vascular parameters between men and women is sparse. Although little data is available, estrogen, progesterone and testosterone are most likely important regulators of blood flow in the retina and choroid, because they are key regulators of vascular tone in other organs. Estrogen seems to play a protective role since it decreases vascular resistance in large ocular vessels. Some studies indicate that hormone therapy is beneficial for ocular vascular disease in post-menopausal women. This evidence is, however, not sufficient to give any recommendation. Generally, remarkably few data are available on the role of sex hormones on ocular blood flow regulation, a topic that requires more attention in the future.

Evaluation of the macula, retinal nerve fiber layer and choroid thickness in postmenopausal women and reproductive-age women using spectral-domain optical coherence tomography

Objective

Menopause is a physiological life period that potentially affects various organs and systems. Therefore, a wide spectrum of signs and symptoms of eyes may be clinically observed in the postmenopausal period.

Aim of the study

To evaluate the macular, retinal nerve fiber layer (RNFL) and choroidal thickness alterations by using spectral-domain optical coherence tomography (SD-OCT) in postmenopausal women and compare with healthy reproductive-age women controls.

Material and methods

The study population included a healthy reproductive-age control group (n = 72) and postmenopausal study group (n = 72). Retinal thickness parameters were measured by SD-OCT. Peripapillary RNFL thickness parameters, macular thickness and choroidal thickness were evaluated.

Results

Superior inner macula, temporal inner macula, inferior inner macula, nasal inner macula, inferior outer macula and choroid thickness were significantly thinner in the postmenopausal study group than the healthy reproductive-age control group (p = 0.007, p = 0.037, p = 0.027, p = 0.006, p = 0.016, p < 0.001, respectively). After adjusting for age, only choroid thickness was significantly thinner in the postmenopausal study group than controls (p^† = 0.005).

Conclusions

This study revealed that choroidal thickness measured by SD-OCT was significantly thinner in postmenopausal women than healthy reproductive-age women. We can speculate that the decrease in choroidal thickness in postmenopausal women may indicate a reduced estrogen-dependent vasodilatory effect in ophthalmic artery secondary to menopausal estrogen deficiency.

Ligusticum chuanxiong Prevents Ovariectomy-Induced Liver and Vascular Damage in Rats

Post-menopause, there is an increase in body weight, visceral adiposity, and risk of developing non-alcoholic fatty liver disease (NAFLD), which leads to various cardiovascular diseases (CVDs). Some natural products have proven useful for counteracting the detrimental effects of menopause. The rhizome of Ligusticum chuanxiong Hort. (LC) is a well-known medicinal herb widely used in Chinese communities for the treatment of CVDs. The hepatic and vascular protective effects of LC ethanolic extract under postmenopausal conditions were investigated on ovariectomized (OVX) rats supplemented with or without LC ethanolic extract (600 mg/kg body weight/day, p.o.) or 17β-estradiol (1 mg/kg body weight/day, p.o.) for 12 weeks. The current findings demonstrated that consumption of LC ethanolic extract could reduce the body weight gain, improve serum lipid profile (lowering low density lipoprotein cholesterol but raising high density lipoprotein cholesterol), combat NAFLD, and protect vascular endothelium in the OVX rats. The beneficial effects of LC may be associated with its antioxidant or vasorelaxant compounds, which enhance the levels of hepatic antioxidant enzymes and up-regulate endothelial nitric oxide synthase mRNA expression, respectively. Taken together, LC may be a promising natural supplement for postmenopausal women to prevent NAFLD and CVDs.

Progesterone increases resistance of ophthalmic and central retinal arteries in climacteric women

OBJECTIVE

To evaluate the effect of a synthetic progestin on the vascular resistance of the ophthalmic and central retinal arteries in climacteric women, compared to placebo, using transorbital ultrasound with Doppler velocimetry.

METHODS

We performed a prospective, randomized, double-blinded, placebo-controlled study with 216 climacteric women. Subjects were randomly allocated to one of two groups: either the group receiving placebo (one pill/day for 30 days) (n = 108) or the group receiving progestin (5 mg medroxyprogesterone acetate/day for 30 days) (n = 108). Transorbital Doppler velocimetric ultrasound was performed, before and after treatment; we measured the pulsatility index, resistance index and systole/diastole ratio.

RESULTS

The mean ages of the participants in the study group and the control group were 54 ± 6.2 years (range 48-59 years) and 55 ± 6.8 years (range 46-60 years), respectively. When we compared the effect of the progestin on the central retinal artery before and after treatment, we observed a significant increase after the treatment in all Doppler indices. The same was observed when we compared the effect of the progestin on the ophthalmic artery. In the group of women receiving placebo, the Doppler indices were similar before and after treatment.

CONCLUSIONS

Our results demonstrate the existence of a progestogenic vasoconstrictive effect in the ophthalmic and central retinal arteries. As this study provides new data, the observed effect needs further investigations to better elucidate its extent. Moreover, our findings may be particularly useful to others interested in understanding the vascular dynamics of the cerebral vessels and to researchers running clinical trials related to hormone replacement therapy.