Reporting of sex as a variable in cardiovascular studies using cultured cells: A systematic review.

Reporting the sex of biological material is critical for transparency and reproducibility in science. This study examined the reporting of the sex of cells used in cardiovascular studies. Articles from 16 cardiovascular journals that publish peer-reviewed studies in cardiovascular physiology and pharmacology in the year 2018 were systematically reviewed using terms "cultured" and "cells." Data were collected on the sex of cells, the species from which the cells were isolated, and the type of cells, and summarized as a systematic review. Sex was reported in 88 (38.6%) of the 228 studies meeting inclusion criteria. Reporting rates varied with Circulation, Cardiovascular Research and American Journal of Physiology: Heart and Circulatory Physiology having the highest rates of sex reporting (>50%). A majority of the studies used cells from male (54.5%) or both male and female animals (32.9%). Humans (31.8%), rats (20.4%), and mice (43.8%) were the most common sources for cells. Cardiac myocytes were the most commonly used cell type (37.0%). Overall reporting of sex of experimental material remains below 50% and is inconsistent among journals. Sex chromosomes in cells have the potential to affect protein expression and molecular signaling pathways and should be consistently reported.

Heterogeneity in treatment effects across diverse populations.

Differences in patient characteristics, including age, sex, and race influence the safety and effectiveness of drugs, biologic products, and medical devices. Here we provide a summary of the topics discussed during the opening panel at the 2018 Johns Hopkins Center for Excellence in Regulatory Science and Innovation symposium on Assessing and Communicating Heterogeneity of Treatment Effects for Patient Subpopulations: Challenges and Opportunities. The goal of this session was to provide a brief overview of FDA-regulated therapeutics, including drugs, biologics and medical devices, and some of the major sources of heterogeneity of treatment effects (HTE) related to patient demographics, such as age, sex and race. The panel discussed the US Food and Drug Administration's role in reviewing and regulating drugs, devices, and biologic products and the challenges associated with ensuring that diverse patient populations benefit from these therapeutics. Ultimately, ensuring diverse demographic inclusion in clinical trials, and designing basic and clinical research studies to account for the intended patient population's age, sex, race, and genetic factors among other characteristics, will lead to better, safer therapies for diverse patient populations.

Loss of Ovarian Hormones and Accelerated Somatic and Mental Aging.

Bilateral oophorectomy in premenopausal women is a unique condition causing the abrupt and premature loss of ovarian hormones, primarily estrogen. Bilateral oophorectomy causes an alteration of several fundamental aging processes at the cellular, tissue, organ, and system levels, leading to multimorbidity, frailty, and reduced survival. However, many questions remain unanswered.

Augmented cerebral blood velocity in response to isometric handgrip exercise in women with a history of preeclampsia.

Preeclampsia (PE) is a hypertensive disorder of pregnancy described as a condition of excessive sympathoexcitation. PE places a woman at increased risk for lifelong hypertension and cognitive impairment. Cerebral blood velocity is blunted in response to a vasoactive stimulus in women with a history of PE. This study investigated how a sympathoexcitatory stimulus affects cerebral blood velocity in women with a history of PE. Middle cerebral artery blood velocity (MCAv) and beat-to-beat mean arterial blood pressure (MAP) were measured in postmenopausal women with a history of PE (n = 21; age = 59 ± 5 yr) and a history of a normotensive pregnancy (NP; n = 27; age = 58 ± 4 yr), at baseline, during isometric handgrip to fatigue (IHG) followed by postexercise ischemia (PEI), and a recovery period (REC). Baseline MAP and MAP responses to IHG and PEI did not differ between groups. MCAv at baseline and throughout the stimulus was lower in PE women compared with NP women (P < 0.05 for all). MCAv increased during IHG in both groups (P < 0.05). This increase in MCAv was greater in PE compared with NP women during IHG and REC (IHG: PE 13 ± 2% vs. NP 9 ± 2%; REC: PE 3 ± 2% vs. NP -2 ± 2%; P < 0.05 for both). Thus, a history of PE is associated with low baseline cerebral blood velocity but an augmented response to a sympathoexcitatory stimulus. These changes in cerebral blood flow regulation may lead to an increased risk for cognitive impairment in women with a history of PE.

Impact of menopausal hormone formulations on pituitary-ovarian regulatory feedback.

Changes in pituitary-ovarian hormones across the menopausal transition have multiple physiological consequences. However, little is known about how the major types of postmenopausal hormone therapy (HT) affect pituitary-ovarian hormonal relationships. This study evaluated these relationships in recently menopausal women (52.45 ± 2.49 yr of age) in the Kronos Early Estrogen Prevention Study (KEEPS) who were compliant to randomized, double-blinded treatment with oral conjugated equine estrogen (o-CEE; n = 109), transdermal 17ß-estradiol (t-E2; n = 107), or placebo (n = 146). Androstenedione, testosterone, 17ß-estradiol, estrone, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) were measured in serum before (baseline) and 48 mo after randomization to treatment. Descriptive summaries of hormone levels were performed, and multiple regression analyses were used to examine the effects of o-CEE, t-E2, and placebo on these hormone levels at 48 mo, adjusting for baseline levels. A network analysis examined the covariance of changes in hormone levels over the 48 mo within treatment groups. As expected, at 48 mo of treatment, hormone levels differed between women in the two active treatment groups compared with placebo, and network analysis indicated stronger relationships among hormone levels in the t-E2 and o-CEE groups compared with placebo. Associations among testosterone, 17ß-estradiol, FSH, and LH differed between the o-CEE group compared with t-E2 and placebo groups. Thus, two common HT regimens differentially alter pituitary-ovarian hormone levels, altering feedback cycles and interhormonal associations in recently menopausal women. These interactions provide the basis for future studies investigating the impact of hormonal modulation of aging, including cognitive decline in women.

Pregnancy History, Hypertension, and Cognitive Impairment in Postmenopausal Women.

PURPOSE OF REVIEW: Risks for developing cardiovascular disease and cognitive decline increase with age. In women, these risks may be influenced by pregnancy history. This review provides an integrated evaluation of associations of pregnancy history with hypertension, brain atrophy, and cognitive decline in postmenopausal women. RECENT FINDINGS: Atrophy in the occipital lobes of the brain was evident in women who had current hypertension and a history of preeclampsia. Deficits in visual memory in women with a history of preeclampsia are consistent with these brain structural changes. The blood velocity response to chemical and sympathoexcitatory stimuli were altered in women with a history of preeclampsia linking impairments in cerebrovascular regulation to the structural and functional changes in the brain. Having a history of preeclampsia should require close monitoring of blood pressure and initiation of anti-hypertensive treatment in perimenopausal women. Mechanisms by which preeclampsia affects cerebrovascular structure and function require additional study.

Considering sex as a biological variable in preclinical research.

In June 2015, the National Institutes of Health (NIH) released a Guide notice (NOT-OD-15-102) that highlighted the expectation of the NIH that the possible role of sex as a biologic variable be factored into research design, analyses, and reporting of vertebrate animal and human studies. Anticipating these guidelines, the NIH Office of Research on Women's Health, in October 2014, convened key stakeholders to discuss methods and techniques for integrating sex as a biologic variable in preclinical research. The workshop focused on practical methods, experimental design, and approaches to statistical analyses in the use of both male and female animals, cells, and tissues in preclinical research. Workshop participants also considered gender as a modifier of biology. This article builds on the workshop and is meant as a guide to preclinical investigators as they consider methods and techniques for inclusion of both sexes in preclinical research and is not intended to prescribe exhaustive/specific approaches for compliance with the new NIH policy.-Miller, L. R., Marks, C., Becker, J. B., Hurn, P. D., Chen, W.-J., Woodruff, T., McCarthy, M. M., Sohrabji, F., Schiebinger, L., Wetherington, C. L., Makris, S., Arnold, A. P., Einstein, G., Miller, V. M., Sandberg, K., Maier, S., Cornelison, T. L., Clayton, J. A. Considering sex as a biological variable in preclinical research.

Sex-Specific Physiology and Cardiovascular Disease.

Sex differences in cardiovascular diseases can be classified as those which are specific to one sex and those that differ in incidence, prevalence, etiology, symptomatology, response to treatment, morbidity, and mortality in one sex compared to the other. All sex differences in cardiovascular conditions have their basis in the combined expression of genetic and hormonal differences between women and men. This chapter addresses how understanding basic mechanisms of hormone responses, imaging diagnostics, and integration of genomics and proteomics has advanced diagnosis and improved outcomes for cardiovascular conditions, apart from those related to pregnancy that are more prevalent in women. These conditions include obstructive coronary artery disease, coronary microvascular dysfunction, spontaneous coronary artery dissection, diseases of the cardiac muscle including heart failure and takotsubo cardiomyopathy, and conditions related to neurovascular dysregulation including hot flashes and night sweats associated with menopause and effects of exogenous hormones on vascular function. Improvement in technologies allowing for noninvasive assessment of neuronally mediated vascular reactivity will further improve our understanding of the basic etiology of the neurovascular disorders. Consideration of sex, hormonal status, and pregnancy history in diagnosis and treatment protocols will improve prevention and outcomes of cardiovascular disease in women as they age.

Women with hypertrophic cardiomyopathy have worse survival.

AIMS: Sex differences in hypertrophic cardiomyopathy (HCM) remain unclear. We sought to characterize sex differences in a large HCM referral centre population. METHODS AND RESULTS: Three thousand six hundred and seventy-three adult patients with HCM underwent evaluation between January 1975 and September 2012 with 1661 (45.2%) female. Kaplan-Meier survival curves were assessed via log-rank test. Cox proportional hazard regression analyses evaluated the relation of sex with survival. At index visit, women were older (59 ± 16 vs. 52 ± 15 years, P < 0.0001) had more symptoms [New York Heart Association (NYHA) Class III-IV 45.0% vs. 35.3%, P < 0.0001], more obstructive physiology (77.4% vs. 71.8%, P = 0.0001), more mitral regurgitation (moderate or greater in 56.1% vs. 43.9%, P < 0.0001), higher E/e' ratio (n = 1649, 20.6 vs. 15.6, P < 0.0001), higher estimated pulmonary artery systolic pressure (n = 1783, 40.8 ± 15.4 vs. 34.8 ± 10.8 mmHg, P < 0.0001), worse cardiopulmonary exercise performance (n = 1267; percent VO2 predicted 62.8 ± 20% vs. 65.8 ± 19.2%, P = 0.007), and underwent more frequent alcohol septal ablation (4.9% vs. 3.0%, P = 0.004) but similar frequency of myectomy (28% vs. 30%, P = 0.24). Median follow-up was 10.9 (IQR 7.4-16.2) years. Kaplan-Meier analysis demonstrated lower survival in women compared with men (P < 0.0001). In multivariable modelling, female sex remained independently associated with mortality (HR 1.13 [1.03-1.22], P = 0.01) when adjusted for age, NYHA Class III-IV symptoms, and cardiovascular comorbidities. CONCLUSION: Women with HCM present at more advanced age, with more symptoms, worse cardiopulmonary exercise tolerance, and different haemodynamics than men. Sex is an important determinant in HCM management as women with HCM have worse survival. Women may require more aggressive diagnostic and therapeutic approaches.

An update on hormone therapy in postmenopausal women: mini-review for the basic scientist.

The worlds of observational, clinical, and basic science collided in 2002 with the publication of results of the Women's Health Initiative (WHI), a large-scale, prospective, blinded, randomized-controlled trial designed to provide evidence regarding use of hormone treatment to prevent cardiovascular disease in menopausal women. The results of the WHI dramatically changed clinical practice, negatively impacted funding for hormone research, and left scientists to unravel the "why" of the results. Now over a decade and a half since the initial publication of the WHI results, basic and clinical scientists often do not interpret the results of the WHI with the precision needed to move the science forward. This review will 1) describe the historical background leading up to the WHI, 2) list the outcomes from the WHI, and put them in perspective with results of subsequent analysis of the WHI data and results from other prospective menopausal hormone treatment trials addressing cardiovascular effects of menopausal hormone use, and 3) articulate how the collective results are influencing current clinical care with the intent to provide guidance for designing and evaluating relevant new hormonal studies.

Sympathetic responsiveness is not increased in women with a history of hypertensive pregnancy.

Hypertensive pregnancy (HTNP) is a risk factor for future cardiovascular disease. Exaggerated cardiovascular responses to physical stress are also considered an independent marker of cardiovascular disease risk. However, there are limited data regarding the blood pressure (BP) responses to acute stress in women, who have a history of HTNP. Hence, the aim of the study is to compare BP responses to a physical stress in postmenopausal women with a history of HTNP to age- and parity-matched women with a history of normotensive pregnancy (NP). Beat-to-beat BP and heart rate was recorded in 64 postmenopausal women with [age = 58.5 (55.2, 62.2) yr, where values are the median, 25th percentile, and 75th percentile] and without [age = 59.4 (55.9, 62.4) yr] a history of HTNP before and during isometric handgrip (IHG) exercise (30% of maximal voluntary contraction) to fatigue. Muscle metaboreflex was measured during postexercise ischemia following IHG exercise. BP variables increased similarly in response to IHG exercise [systolic: NP = 11.5 (8.9, 17.6) %, HTNP = 11.3 (9.5, 15.9) %; diastolic NP = 11.2 (7.9, 13.3) %, HTNP = 9.5 (7.1, 14.3) %; mean blood pressure: NP = 9.8 (5.0, 13.6) %, and HTNP = 7.2 (4.4, 10.4) %] and postexercise ischemia [systolic: NP = 14.1 (10.3, 23.0) %, HTNP = 15.8 (10.6, 21.4) %; diastolic NP = 12.2 (4.8, 17.0) %, HTNP = 10.4 (5.3, 17.1) %; and mean blood pressure: NP = 11.1 (6.1, 17.9) %, HTNP = 9.4 (2.9, 14.8) %] in both groups. Although having a history of HTNP is associated with future cardiovascular disease risk, results from this study suggest that the risk may not be manifested through altered cardiovascular metaboreflex response to physical stressors.

Preeclampsia and ESRD: The Role of Shared Risk Factors.

BACKGROUND: Several registry-based studies, using diagnostic codes, have suggested that preeclampsia is a risk factor for end-stage renal disease (ESRD). However, because the 2 diseases share risk factors, the true nature of their association remains uncertain. Our goals were to conduct a population-based study to determine the magnitude of the association between preeclampsia and ESRD and evaluate the role of shared risk factors. STUDY DESIGN: Population-based nested case-control study. SETTING & PARTICIPANTS: The US Renal Data System was used to identify women with ESRD from a cohort of 34,581 women who gave birth in 1976 to 2010 in Olmsted County, MN. 44 cases of ESRD were identified and each one was matched to 2 controls based on year of birth (±1 year), age at first pregnancy (±2 years), and parity (±1 or ≥4). PREDICTOR: Preeclamptic pregnancy, confirmed by medical record review. OUTCOME: ESRD. MEASUREMENTS: Prepregnancy serum creatinine and urine protein measurements were recorded. Comorbid conditions existing prior to pregnancy were abstracted from medical records and included kidney disease, obesity, diabetes, and hypertension. RESULTS: There was evidence of kidney disease prior to the first pregnancy in 9 of 44 (21%) cases and 1 of 88 (<1%) controls. Per chart review, 8 of 44 (18%) cases versus 4 of 88 (5%) controls had preeclamptic pregnancies (unadjusted OR, 4.0; 95% CI, 1.21-13.28). Results were similar after independent adjustment for race, education, diabetes, and hypertension prior to pregnancy. However, the association was attenuated and no longer significant after adjustment for obesity (OR, 3.25; 95% CI, 0.93-11.37). LIMITATIONS: The limited number of ESRD cases and missing data for prepregnancy kidney function. CONCLUSIONS: Our findings confirm that there is a sizable association between preeclampsia and ESRD; however, obesity is a previously unexplored confounder. Pre-existing kidney disease was common, but not consistently coded or diagnosed.

Preeclampsia and cognitive impairment later in life.

BACKGROUND: Hypertension is a risk factor for cerebrovascular disease and cognitive impairment. Women with hypertensive episodes during pregnancy report variable neurocognitive changes within the first decade following the affected pregnancy. However, long-term follow-up of these women into their postmenopausal years has not been conducted. OBJECTIVE: The aim of this study was to examine whether women with a history of preeclampsia were at increased risk of cognitive decline 35-40 years after the affected pregnancy. STUDY DESIGN: Women were identified and recruited through the medical linkage, population-based Rochester Epidemiologic Project. Forty women with a history of preeclampsia were age- and parity-matched to 40 women with a history of normotensive pregnancy. All women underwent comprehensive neuropsychological assessment and completed self-report inventories measuring mood, ie, depression, anxiety, and other symptoms related to emotional state. Scores were compared between groups. In addition, individual cognitive scores were examined by neuropsychologists and a neurologist blinded to pregnancy status, and a clinical consensus diagnosis of normal, mild cognitive impairment, or dementia for each participant was conferred. RESULTS: Age at time of consent did not differ between preeclampsia (59.2 [range 50.9-71.5] years) and normotensive (59.6 [range 52.1-72.2] years) groups, nor did time from index pregnancy (34.9 [range 32.0-47.2] vs 34.5 [range 32.0-46.4] years, respectively). There were no statistically significant differences in raw scores on tests of cognition and mood between women with histories of preeclampsia compared to women with histories of normotensive pregnancy. However, a consensus diagnosis of mild cognitive impairment or dementia trended toward greater frequency in women with histories of preeclampsia compared to those with normotensive pregnancies (20% vs 8%, P = .10) and affected more domains among the preeclampsia group (P = .03), most strongly related to executive dysfunction (d = 1.96) and verbal list learning impairment (d = 1.93). CONCLUSION: These findings suggest a trend for women with a history of preeclampsia to exhibit more cognitive impairment later in life than those with a history of normotensive pregnancy. Furthermore, the pattern of cognitive changes is consistent with that observed with vascular disease/white matter pathology.

Pharmacogenomics of estrogens on changes in carotid artery intima-medial thickness and coronary arterial calcification: Kronos Early Estrogen Prevention Study.

Prior to the initiation of menopausal hormone treatment (MHT), genetic variations in the innate immunity pathway were found to be associated with carotid artery intima-medial thickness (CIMT) and coronary arterial calcification (CAC) in women (n = 606) enrolled in the Kronos Early Estrogen Prevention Study (KEEPS). Whether MHT might affect these associations is unknown. The association of treatment outcomes with variation in the same 764 candidate genes was evaluated in the same KEEPS participants 4 yr after randomization to either oral conjugated equine estrogens (0.45 mg/day), transdermal 17ß-estradiol (50 µg/day), each with progesterone (200 mg/day) for 12 days each month, or placebo pills and patch. Twenty SNPs within the innate immunity pathway most related with CIMT after 4 yr were not among those associated with CIMT prior to MHT. In 403 women who completed the study in their assigned treatment group, single nucleotide polymorphisms (SNPs) within the innate immunity pathway were found to alter the treatment effect on 4 yr change in CIMT (i.e., significant interaction between treatment and genetic variation in the innate immunity pathway; P < 0.001). No SNPs by treatment effects were observed with changes of CAC >5 Agatston units after 4 yr. Results of this study suggest that hormonal status may interact with genetic variants to influence cardiovascular phenotypes, specifically, the pharmacogenomic effects within the innate immunity pathway for CIMT.

Genetic loci associated with nonobstructive coronary artery disease in Caucasian women.

Nonobstructive coronary artery disease (CAD) in women is associated with adverse cardiovascular (CV) outcomes; however, information regarding genetic variants that predispose women to nonobstructive CAD is lacking. Women from the Women's Ischemia Syndrome Evaluation (WISE) Study and the St. James Women Take Heart (WTH) Study were genotyped with the Cardio-MetaboChip. WISE enrolled women with symptoms and signs of ischemia referred for coronary angiography; WTH enrolled asymptomatic, community-based women without heart disease. Analyses were conducted with a case (WISE)--control (WTH) design and multivariate logistic regression models to investigate genetic variation associated with likelihood of nonobstructive CAD. One genetic marker, single nucleotide polymorphism (SNP) rs2301753 on chromosome 6 in RNF39, achieved chip-wide significance for nonobstructive CAD (P < 9.5 × 10(-7)). After adjusting for baseline characteristics, we found no variants achieved chip-wide significance. However, SNP rs2301753 on chromosome 6 in RNF39 was associated with reduced likelihood of nonobstructive CAD [odds ratio (OR) 0.42 and 95% confidence interval (CI) of 0.29 to 0.68], at a nominal level of P = 5.6 × 10(-6), while SNP rs12818945 in the ATP2B1 locus on chromosome 12 was associated with increased odds for nonobstructive CAD (OR 2.38 and 95% CI of 1.63 to 3.45) and nominal P = 5.8 × 10(-6). The functions of RNF39 and ATP2B1 raise the possibility that genes involved in cardio-dysfunction may contribute to nonobstructive CAD in Caucasian women and may provide insights into novel approaches for therapy and prevention. If replicated, incorporation of these genetic variants into diagnostic evaluation may identify women at high risk for nonobstructive CAD.

Sex hormone therapy and progression of cardiovascular disease in menopausal women.

One of the most controversial health decisions facing women is deciding upon the use of hormonal treatments for symptoms of menopause. This brief review focuses on the historical context of use of menopausal hormone treatments (MHT), summarizes results of major observational, primary and secondary prevention studies of MHT and cardiovascular (CV) outcomes, provides evidence for how sex steroids modulate CV function and identifies challenges for future research. As medicine enters an era of personalization of treatment options, additional research into sex differences in the aetiology of CV diseases will lead to better risk identification for CV disease in women and identify whether a woman might receive CV benefit from specific formulations and doses of MHT.

A history of preeclampsia is associated with a risk for coronary artery calcification 3 decades later.

BACKGROUND: A history of preeclampsia is an independent risk factor for cardiac events and stroke. Changes in vasculature structure that contribute to these associations are not well understood. OBJECTIVE: The aim of this study was to quantify coronary artery calcification (CAC), a known risk factor for cardiac events, in a prospective cohort of women with and without histories of preeclampsia. STUDY DESIGN: Women without prior cardiovascular events (40 with and 40 without histories of preeclampsia, matched for parity and age at index birth) were recruited from a large population-based cohort of women who were residents of Olmsted County, Minnesota, and who delivered from 1976 through 1982. Computed tomography was performed to measure CAC in Agatston units. All pregnancy histories and covariates were confirmed by review of the medical records. Current clinical variables were assessed at the time of imaging. Differences between women with and without histories of preeclampsia were examined using χ(2) tests and tests; CAC, in particular, was compared as a categorical and ordinal variable, with a χ(2) test and with Wilcoxon 2-sample tests and ordinal logistic regression, as appropriate. RESULTS: Mean age (SD) at imaging was 59.5 (±4.6) years. Systolic and diastolic blood pressures, hyperlipidemia, and current diabetes status did not differ between women with and without histories of preeclampsia. However, the frequencies of having a current clinical diagnosis of hypertension (60% vs 20%, P < .001) and higher body mass index in kg/m(2) (expressed as median [25th-75th percentile], 29.8 [25.9-33.7] vs 25.3 [23.1-32.0], P = .023) were both greater in the women with histories of preeclampsia compared to those without. The frequency of a CAC score >50 Agatston units was also greater in the preeclampsia group (23% vs 0%, P = .001). Compared to women without preeclampsia, the odds of having a higher CAC score was 3.54 (confidence interval [CI], 1.39-9.02) times greater in women with prior preeclampsia without adjustment, and 2.61 (CI, 0.95-7.14) times greater after adjustment for current hypertension. After adjustment for body mass index alone, the odds of having a higher CAC based on a history of preeclampsia remained significant at 3.20 (CI, 1.21-8.49). CONCLUSION: In this first prospective cohort study with confirmation of preeclampsia by medical record review, a history of preeclampsia is associated with an increased risk of CAC >30 years after affected pregnancies, even after controlling individually for traditional risk factors. A history of preeclampsia should be considered in risk assessment when initiating primary prevention strategies to reduce cardiovascular disease in women. Among women with histories of preeclampsia, the presence of CAC may be able to identify those at a particularly high cardiovascular risk, and should be the subject of future studies.

Longitudinal effects of menopausal hormone treatments on platelet characteristics and cell-derived microvesicles.

Activated platelets serve as a catalyst for thrombin generation and a source of vasoactive and mitogenic factors affecting vascular remodeling. Oral menopausal hormone treatments (MHT) may carry greater thrombotic risk than transdermal products. This study compared effects of oral and transdermal MHT on platelet characteristics, platelet proteins, and platelet-derived microvesicles (MV) in recently menopausal women. Platelets and MV were prepared from blood of a subset of women (n = 117) enrolled in the Kronos Early Estrogen Prevention Study prior to and after 48 months of treatment with either oral conjugated equine estrogen (0.45 mg/day), transdermal 17ß-estradiol (50 µg/day), each with intermittent progesterone (200 mg/day for 12 days a month), or placebo pills and patch. Platelet count and expression of platelet P-selectin and fibrinogen receptors were similar across groups. An aggregate measure of 4-year change in vasoactive and mitogenic factors in platelet lysate, by principle component analysis, indicated significantly lower values in both MHT groups compared to placebo. Increases in numbers of tissue factor positive and platelet-derived MV were significantly greater in the transdermal compared to placebo group. MHT was associated with significantly reduced platelet content of vasoactive and mitogenic factors representing a potential mechanism by which MHT may affect vascular remodeling. Various hormonal compositions and doses of MHT could differentially regulate nuclear transcription in bone marrow megakaryocytes and non-genomic pathways in circulating platelets thus determining numbers and characteristics of circulating MV. Thrombotic risk associated with oral MHT most likely involves liver-derived inflammatory/coagulation proteins rather than circulating platelets per se.