The Use of Injectable Estradiol in Transgender and Gender Diverse Adults: A Scoping Review of Dose and Serum Estradiol Levels.

OBJECTIVE: Feminizing gender-affirming hormone therapy is the mainstay of treatment for many transgender and gender diverse people. Injectable estradiol preparations are recommended by the World Professional Association for Transgender Health Standards of Care 8 and the Endocrine Society guidelines. Many patients prefer this route of administration, but few studies have rigorously assessed optimal dosing or route. METHODS: We performed a scoping review of the available data on estradiol levels achieved with various dosages of estradiol injections in transgender and gender diverse adults on feminizing gender-affirming hormone therapy. We also report on testosterone suppression, route (ie, subcutaneous vs intramuscular), and type of injectable estradiol ester as well as timing of blood draw relative to the most recent dose, where available. RESULTS: The data we reviewed suggest that the current guidelines, which recommend starting doses 2 to 10 mg weekly or 5 to 30 mg every 2 weeks of estradiol cypionate or valerate, are too high and likely lead to patients having supraphysiologic levels across much of their injection cycle. CONCLUSIONS: The optimal starting dose for injectable estradiol remains unclear and whether it should differ for cypionate and valerate. Based on the data available, we suggest that clinicians start injectable estradiol cypionate or valerate via subcutaneous or intramuscular injections at a dose ≤5 mg weekly and then titrate accordingly to keep levels within guideline-recommended range. Future studies should assess timing of injections and subsequent levels more precisely across the injection cycle and between esters.

The role of menopausal hormone therapy in the prevention and treatment of low bone density in perimenopausal and postmenopausal women.

PURPOSE OF REVIEW: The purpose of this review is to summarize the evidence on the benefits of menopausal hormone therapy (MHT) for the maintenance of skeletal health, prevention of osteoporosis and related fractures in peri and postmenopausal women. RECENT FINDINGS: We will review the impact of estrogen on skeletal health as well as the physiology of bone loss during the perimenopause and postmenopause. We will then elucidate the data that include estrogen alone and combination of MHT to demonstrate that in the absence of contraindication, MHT should be considered as an option for the maintenance of skeletal health both when concomitant menopausal symptoms are present and when not. SUMMARY: It has been well established that estrogens maintain bone mineral density (BMD) and reduce fracture risk at all sites. However, the most extensively studied form of estrogen with established fracture prevention is oral doses of synthetic estrogens. Due to the reduced risk profile, lower doses of bioidentical oral or transdermal estrogens are often preferred in clinical practice. We will highlight the current data on improvement in BMD and fracture risk reduction, including differences in formulation, dose, and route of delivery, to support a provider in the clinical decision-making process.

Perimenopausal contraception.

PURPOSE OF REVIEW: Perimenopause is a time of reduced fertility, and yet unintended pregnancies can occur making comprehensive contraceptive counseling essential for these women. Concern over potential contraceptive risks has unnecessarily limited access and use of certain hormonal methods in this population. This review summarizes the available data on the use and effectiveness of contraceptive options during perimenopause. RECENT FINDINGS: All contraceptive options may be appropriate during perimenopause and no method is contraindicated based on age alone. Combined hormonal contraception has the added benefit of relieving perimenopausal symptoms including controlling menstrual irregularities. Progestin-only methods have the advantage of being taken either alone or in combination with estrogen replacement therapy to address both perimenopausal symptoms and contraceptive needs. Nonhormonal options exist for those wishing to avoid hormonal methods. SUMMARY: Extensive contraceptive options are available for perimenopausal women as they transition into menopause. Consideration of patient preference, medical co-morbidities, and perimenopausal symptoms will allow women to use the option that best serves her needs.

Pancreatic beta cell function following liraglutide-augmented weight loss in individuals with prediabetes: analysis of a randomised, placebo-controlled study.

AIMS/HYPOTHESIS: Liraglutide can modulate insulin secretion by directly stimulating beta cells or indirectly through weight loss and enhanced insulin sensitivity. Recently, we showed that liraglutide treatment in overweight individuals with prediabetes (impaired fasting glucose and/or impaired glucose tolerance) led to greater weight loss (-7.7% vs -3.9%) and improvement in insulin resistance compared with placebo. The current study evaluates the effects on beta cell function of weight loss augmented by liraglutide compared with weight loss alone. METHODS: This was a parallel, randomised study conducted in a single academic centre. Both participants and study administrators were blinded to treatment assignment. Individuals who were 40-70 years old, overweight (BMI 27-40 kg/m(2)) and with prediabetes were randomised (via a computerised system) to receive liraglutide (n = 35) or matching placebo (n = 33), and 49 participants were analysed. All were instructed to follow an energy-restricted diet. Primary outcome was insulin secretory function, which was evaluated in response to graded infusions of glucose and day-long mixed meals. RESULTS: Liraglutide treatment (n = 24) significantly (p ≤ 0.03) increased the insulin secretion rate (% mean change [95% CI]; 21% [12, 31] vs -4% [-11, 3]) and pancreatic beta cell sensitivity to intravenous glucose (229% [161, 276] vs -0.5% (-15, 14]), and decreased insulin clearance rate (-3.5% [-11, 4] vs 8.2 [0.2, 16]) as compared with placebo (n = 25). The liraglutide-treated group also had significantly (p ≤ 0.03) lower day-long glucose (-8.2% [-11, -6] vs -0.1 [-3, 2]) and NEFA concentrations (-14 [-20, -8] vs -2.1 [-10, 6]) following mixed meals, whereas day-long insulin concentrations did not significantly differ as compared with placebo. In a multivariate regression analysis, weight loss was associated with a decrease in insulin secretion rate and day-long glucose and insulin concentrations in the placebo group (p ≤ 0.05), but there was no association with weight loss in the liraglutide group. The most common side effect of liraglutide was nausea. CONCLUSIONS/INTERPRETATION: A direct stimulatory effect on beta cell function was the predominant change in liraglutide-augmented weight loss. These changes appear to be independent of weight loss. TRIAL REGISTRATION: ClinicalTrials.gov NCT01784965 FUNDING: The study was funded by the ADA.

Effect of Pioglitazone on Cardiometabolic Risk in Patients With Obstructive Sleep Apnea.

Prevalence of insulin resistance is increased in patients with obstructive sleep apnea (OSA). Because insulin resistance is an independent predictor of cardiovascular disease (CVD), this study was initiated to see if pioglitazone administration would improve insulin sensitivity and thereby decrease risk of CVD in overweight/obese, nondiabetic, insulin-resistant patients with untreated OSA. Patients (n = 30) were administered pioglitazone (45 mg/day) for 8 weeks, and measurements were made before and after intervention of insulin action (insulin-mediated glucose uptake by the insulin suppression test), C-reactive protein, lipid/lipoprotein profile, and gene expression profile of periumbilical subcutaneous fat tissue. Insulin sensitivity increased 31% (p <0.001) among pioglitazone-treated subjects, associated with a decrease in C-reactive protein concentration (p ≤0.001), a decrease in plasma triglyceride, and increase in high-density lipoprotein cholesterol concentrations (p ≤0.001), accompanied by significant changes in apolipoprotein A1 and B concentrations and lipoprotein subclasses known to decrease CVD risk. In addition, subcutaneous adipose tissue gene expression profile showed a 1.6-fold (p <0.01) increase in GLUT4 expression and decreased expression in 5 of 9 inflammatory genes (p <0.05). In conclusion, enhanced insulin sensitivity can significantly decrease multiple cardiometabolic risk factors in patients with untreated OSA, consistent with the view that coexisting insulin resistance plays an important role in the association between OSA and increased risk of CVD.

Does enhanced insulin sensitivity improve sleep measures in patients with obstructive sleep apnea: a randomized, placebo-controlled pilot study.

BACKGROUND: High fasting insulin levels have been reported to predict development of observed apneas, suggesting that insulin resistance may contribute to the pathogenesis of obstructive sleep apnea (OSA). The aim of this study was to determine whether enhancing insulin sensitivity in individuals with OSA would improve sleep measures. PATIENTS/METHODS: Insulin-resistant, nondiabetic individuals with untreated OSA were randomized (2:1) to pioglitazone (45 mg/day) or placebo for eight weeks in this single-blind study. All individuals had repeat measurements pertaining to sleep (overnight polysomnography and functional outcomes of sleep questionnaire) and insulin action (insulin suppression test). RESULTS: A total of 45 overweight/obese men and women with moderate/severe OSA were randomized to pioglitazone (n = 30) or placebo (n = 15). Although insulin sensitivity increased 31% among pioglitazone-treated compared with no change among individuals receiving placebo (p <0.001 for between-group difference), no improvement in quantitative or qualitative sleep measurements was observed. CONCLUSIONS: Pioglitazone administration increased insulin sensitivity in otherwise untreated individuals with OSA, without any change in polysomnographic sleep measures over an eight-week period. These findings do not support a causal role for insulin resistance in the pathogenesis of OSA.

Salsalate-induced changes in lipid, lipoprotein, and apoprotein concentrations in overweight or obese, insulin-resistant, nondiabetic individuals.

BACKGROUND AND OBJECTIVE: Although salsalate administration consistently lowers plasma triglyceride concentrations in patients with type II diabetes, prediabetes, and/or insulin resistance, changes in low-density lipoprotein cholesterol (LDL-C) concentrations have been inconsistent; varying from no change to a significant increase. To evaluate the clinical relevance of this discordance in more detail, we directly measured LDL-C and obtained a comprehensive assessment of changes in lipid, lipoprotein, and apoprotein concentrations associated with salsalate use in insulin-resistant individuals, overweight or obese, but without diabetes, using vertical auto profile method. METHODS: A single-blind, randomized, placebo-controlled study was performed in volunteers who were overweight or obese, without diabetes, and insulin resistant on the basis of their steady-state plasma glucose concentration during an insulin suppression test. Participants were randomized 2:1 to receive salsalate 3.5 g/d (n = 27) or placebo (n = 14) for 4 weeks. Comprehensive lipid, lipoprotein, and apoprotein analysis by vertical auto profile was obtained after an overnight fast, before and after study intervention. RESULTS: There was no change in directly measured LDL-C concentration in salsalate-treated individuals. However, salsalate administration was associated with various changes considered to decrease atherogenicity; including decreases in triglyceride and total very low-density lipoprotein cholesterol (VLDL-C) concentrations, a shift from small denser LDL lipoproteins toward larger, more buoyant LDL particles, decreases in VLDL(1+2)-C and LDL(4)-C, and nonsignificant decreases in non-high-density lipoprotein cholesterol and apolipoprotein B. No significant changes occurred in the placebo-treated group. CONCLUSIONS: Atherogenicity of the lipid, lipoprotein, and apoprotein profile of insulin-resistant individuals who were overweight or obese improved significantly in association with salsalate treatment. The clinical importance of this finding awaits further study.

Abnormalities of lipoprotein concentrations in obstructive sleep apnea are related to insulin resistance.

STUDY OBJECTIVE: Prevalence of cardiovascular disease (CVD) is increased in patients with obstructive sleep apnea (OSA), possibly related to dyslipidemia in these individuals. Insulin resistance is also common in OSA, but its contribution to dyslipidemia of OSA is unclear. The study's aim was to define the relationships among abnormalities of lipoprotein metabolism, clinical measures of OSA, and insulin resistance. DESIGN: Cross-sectional study. OSA severity was defined by the apnea-hypopnea index (AHI) during polysomnography. Hypoxia measures were expressed as minimum and mean oxygen saturation, and the oxygen desaturation index. Insulin resistance was quantified by determining steady-state plasma glucose (SSPG) concentrations during the insulin suppression test. Fasting plasma lipid/lipoprotein evaluation was performed by vertical auto profile methodology. SETTING: Academic medical center. PARTICIPANTS: 107 nondiabetic, overweight/obese adults. MEASUREMENTS AND RESULTS: Lipoprotein particles did not correlate with AHI or any hypoxia measures, nor were there differences noted by categories of OSA severity. By contrast, even after adjustment for age, sex, and BMI, SSPG was positively correlated with triglycerides (r = 0.30, P < 0.01), very low density lipoprotein (VLDL) and its subclasses (VLDL1+2) (r = 0.21-0.23, P < 0.05), and low density lipoprotein subclass 4 (LDL4) (r = 0.30, P < 0.01). SSPG was negatively correlated with high density lipoprotein (HDL) (r = -0.38, P < 0.001) and its subclasses (HDL2 and HDL3) (r = -0.32, -0.43, P < 0.01), and apolipoprotein A1 (r = -0.33, P < 0.01). Linear trends of these lipoprotein concentrations across SSPG tertiles were also significant. CONCLUSIONS: Pro-atherogenic lipoprotein abnormalities in obstructive sleep apnea (OSA) are related to insulin resistance, but not to OSA severity or degree of hypoxia. Insulin resistance may represent the link between OSA-related dyslipidemia and increased cardiovascular disease risk.

Usefulness of fetuin-A to predict risk for cardiovascular disease among patients with obstructive sleep apnea.

Patients with obstructive sleep apnea (OSA) are at increased risk for cardiovascular diseases (CVDs). Fetuin-A, a novel hepatokine, has been associated with the metabolic syndrome (MetS), insulin resistance, and type 2 diabetes mellitus, all of which are highly prevalent in patients with OSA and associated with increased CVD risk. The goal of this study was to determine whether fetuin-A could be involved in the pathogenesis of CVD risk in patients with OSA, through relations of fetuin-A with MetS components and/or insulin resistance. Overweight or obese, nondiabetic volunteers (n = 120) were diagnosed with OSA by in-laboratory nocturnal polysomnography. Steady-state plasma glucose concentrations derived during the insulin suppression test were used to quantify insulin-mediated glucose uptake; higher steady-state plasma glucose concentrations indicated greater insulin resistance. Fasting plasma fetuin-A and lipoprotein concentrations were measured. Whereas neither the prevalence of MetS nor the number of MetS components was associated with tertiles of fetuin-A concentrations, the lipoprotein components of MetS, triglycerides and high-density lipoprotein cholesterol, increased (p <0.01) and decreased (p <0.05), respectively, across fetuin-A tertiles. Additionally, comprehensive lipoprotein analysis revealed that very low density lipoprotein (VLDL) particles and VLDL subfractions (VLDL1+2 and VLDL3) were increased across fetuin-A tertiles. In contrast, neither insulin resistance nor sleep measurements related to OSA were found to be modified by fetuin-A concentrations. In conclusion, abnormalities of lipoprotein metabolism, but not MetS or insulin resistance per se, may represent a mechanism by which fetuin-A contributes to increased CVD risk in patients with OSA.

Modulation of coronary heart disease risk by insulin resistance in subjects with normal glucose tolerance or prediabetes.

AIMS: This study was based on the hypothesis that: (1) coronary heart disease (CHD) risk is accentuated in the insulin-resistant subset of persons with normal glucose tolerance (NGT) or prediabetes (PreDM); (2) the prevalence of insulin resistance, and associated abnormalities, is greater in subjects with PreDM; and (3) insulin resistance is the major contributor to increased CHD risk in these individuals. METHODS: A 75 g oral glucose challenge was used to classify volunteers as having NGT or PreDM. Steady-state plasma glucose (SSPG) concentrations during the insulin suppression test subdivided both groups into insulin sensitive (IS = SSPG < 8.4 mmol/L) or resistant (IR = SSPG ≥ 8.4 mmol/L). Measurements were made of demographic characteristics, blood pressure, and lipid and lipoprotein concentrations, and comparisons made between the subgroups. RESULTS: Subjects with PreDM (n = 127) were somewhat older, more likely to be non-Hispanic men, with increased adiposity than those with NGT (n = 315). In addition, they had higher FPG concentrations, were insulin resistant (SSPG concentration; 11.4 vs. 7.2 mmol/L), with higher blood pressures, and a significantly more adverse CHD risk lipid profile (p < 0.001). Twice as many subjects with PreDM were IR (72 vs. 35 %), and the CHD risk profile was significantly worse in the IR subgroups in those with either NGT or PreDM. CONCLUSIONS: Coronary heart disease risk profile is significantly more adverse in subjects with PreDM as compared to individuals with NGT. However, glucose tolerance status is not the only determinant of CHD risk in nondiabetic individuals, and differences in degree of insulin resistance significantly modulate CHD risk in subjects with NGT or PreDM.

Effect of salsalate on insulin action, secretion, and clearance in nondiabetic, insulin-resistant individuals: a randomized, placebo-controlled study.

OBJECTIVE: Salsalate treatment has been shown to improve glucose homeostasis, but the mechanism remains unclear. The aim of this study was to evaluate the effect of salsalate treatment on insulin action, secretion, and clearance rate in nondiabetic individuals with insulin resistance. RESEARCH DESIGN AND METHODS: This was a randomized (2:1), single-blind, placebo-controlled study of salsalate (3.5 g daily for 4 weeks) in nondiabetic individuals with insulin resistance. All individuals had measurement of glucose tolerance (75-g oral glucose tolerance test), steady-state plasma glucose (SSPG; insulin suppression test), and insulin secretion and clearance rate (graded-glucose infusion test) before and after treatment. RESULTS: Forty-one individuals were randomized to salsalate (n = 27) and placebo (n = 14). One individual from each group discontinued the study. Salsalate improved fasting (% mean change -7% [95% CI -10 to -14] vs. 1% [-3 to 5], P = 0.005) but not postprandial glucose concentration compared with placebo. Salsalate also lowered fasting triglyceride concentration (-25% [-34 to -15] vs. -6% [-26 to 14], P = 0.04). Salsalate had no effect on SSPG concentration or insulin secretion rate but significantly decreased insulin clearance rate compared with placebo (-23% [-30 to -16] vs. 3% [-10 to 15], P < 0.001). Salsalate was well tolerated, but four individuals needed a dose reduction due to symptoms. CONCLUSIONS: Salsalate treatment in nondiabetic, insulin-resistant individuals improved fasting, but not postprandial, glucose and triglyceride concentration. These improvements were associated with a decrease in insulin clearance rate without change in insulin action or insulin secretion.

Clinical characteristics and pituitary dysfunction in patients with metastatic cancer to the sella.

OBJECTIVE: Metastatic disease to the sella is uncommon and there are limited available data regarding the clinical aspects of this disease. We therefore sought to characterize the clinical demographics of sellar metastases. METHODS: Retrospective chart review of adults treated at Stanford University Medical Center from 1980 to 2011 with metastatic disease to the sella. RESULTS: A total of 13 subjects were identified (9 females). The mean age at diagnosis was 55 years (range, 25 to 73 years). A total of 6 patients (46%) had breast carcinoma, 3 (23%) had renal cell carcinoma, 2 (15%) had squamous cell carcinoma of the head and neck, 1 had bronchoalveolar carcinoma of the lung, and 1 had nodular sclerosing Hodgkin's lymphoma. The most common presenting signs and symptoms were headache (58%), followed by fatigue (50%), polyuria (50%), visual field defects (42%), and ophthalmoplegia (42%). Seventy-five percent of patients presented with at least one pituitary hormone insufficiency, which included 6 patients (50%) with diabetes insipidus (DI). Eight (67%) subjects had secondary hypothyroidism and 5 (45%) had secondary adrenal insufficiency. Of the patients with stalk involvement, 86% had DI. All patients had a prior diagnosis of malignancy, with a mean duration of 95 months. CONCLUSION: The most common neoplastic sources to the sella were breast and renal cell carcinomas. Secondary hypothyroidism was the most common endocrine abnormality, followed by DI and adrenal insufficiency. New-onset central hypothyroidism and DI along with known malignancy in a patient with a sellar lesion should raise the suspicion of a metastatic source.

Benefits of liraglutide treatment in overweight and obese older individuals with prediabetes.

OBJECTIVE: The aim was to evaluate the ability of liraglutide to augment weight loss and improve insulin resistance, cardiovascular disease (CVD) risk factors, and inflammation in a high-risk population for type 2 diabetes (T2DM) and CVD. RESEARCH DESIGN AND METHODS: We randomized 68 older individuals (mean age, 58±8 years) with overweight/obesity and prediabetes to this double-blind study of liraglutide 1.8 mg versus placebo for 14 weeks. All subjects were advised to decrease calorie intake by 500 kcal/day. Peripheral insulin resistance was quantified by measuring the steady-state plasma glucose (SSPG) concentration during the insulin suppression test. Traditional CVD risk factors and inflammatory markers also were assessed. RESULTS: Eleven out of 35 individuals (31%) assigned to liraglutide discontinued the study compared with 6 out of 33 (18%) assigned to placebo (P=0.26). Subjects who continued to use liraglutide (n=24) lost twice as much weight as those using placebo (n=27; 6.8 vs. 3.3 kg; P<0.001). Liraglutide-treated subjects also had a significant improvement in SSPG concentration (-3.2 vs. 0.2 mmol/L; P<0.001) and significantly (P≤0.04) greater lowering of systolic blood pressure (-8.1 vs. -2.6 mmHg), fasting glucose (-0.5 vs. 0 mmol/L), and triglyceride (-0.4 vs. -0.1 mmol/L) concentration. Inflammatory markers did not differ between the two groups, but pulse increased after liraglutide treatment (6.4 vs. -0.9 bpm; P=0.001). CONCLUSIONS: The addition of liraglutide to calorie restriction significantly augmented weight loss and improved insulin resistance, systolic blood pressure, glucose, and triglyceride concentration in this population at high risk for development of T2DM and CVD.

The role and regulation of microRNAs in asthma.

PURPOSE OF REVIEW: Asthma is a common chronic inflammatory airway disorder that is characterized by variable and recurring airflow obstruction, chronic airway inflammation and bronchial hyper-responsiveness. The etiopathogenesis of asthma remains a complex issue. The intricacy in developing a more effective therapeutic strategy may be due to a large diversity in causative agents and a lack of understanding of the precise molecular mechanism involved in asthma. However, recent identification of microRNAs (miRs) has enhanced technological abilities to understand the disease process. RECENT FINDINGS: miRs regulate gene expression by controlling the translation of a specific type of messenger RNA. miRs have been recently identified as key regulatory RNAs with immense significance in numerous biological processes including asthma. miRs have been implicated to have a fundamental role in acute and chronic asthma and in airway remodeling by the regulation of multiple signal transduction pathways that are involved in the pathogenesis of asthma. It is possible that miRs may bring a fundamental change to our understanding of the pathophysiology of asthma. This may then lead to the development of novel efficacious therapeutic strategies in asthma. SUMMARY: In this review, we highlight the current understanding of the role and regulation of miRs in asthma.

Relations between obesity, insulin resistance, and 25-hydroxyvitamin D.

BACKGROUND: Although low circulating 25-hydroxyvitamin D [25(OH)D] concentrations have been associated with insulin resistance and obesity, the relations between these 3 variables have not been completely resolved. OBJECTIVE: The objective was to compare circulating 25(OH)D concentrations in apparently healthy individuals who were matched for degree of obesity or insulin sensitivity. DESIGN: This was a case-control study in which 78 apparently healthy individuals were classified as being normal weight (NW) or obese (OB) on the basis of their BMI and as being insulin sensitive (IS) or insulin resistant (IR) on the basis of their steady state plasma glucose (SSPG) concentration during the insulin suppression test. RESULTS: Groups did not differ in terms of age, sex distribution, race, or mean (± SD) plasma 25(OH)D concentration. Values for 25(OH)D were 32 ± 10, 30 ± 10, and 28 ± 8 ng/mL in NW-IS, OB-IS, and OB-IR groups, respectively. These concentrations were essentially identical when comparing IR with IS subjects matched for BMI or when comparing OB with NW subjects matched for SSPG. Concentrations of 25(OH)D ≤ 30 ng/mL were somewhat more common in OB subjects than in NW subjects (54% compared with 35%), but SSPG concentrations were not different within either the IR or IS groups when subgroups with 25(OH)D concentrations ≤ 30 or > 30 ng/mL were compared. CONCLUSIONS: In 78 individuals, 47% of whom were vitamin D deficient or insufficient (≤ 30 ng/mL), 25(OH)D concentrations did not vary with differences in insulin sensitivity (SSPG concentration) when matched for BMI (OB-IR compared with OB-IS). Similarly, when matched for SSPG concentrations, plasma 25(OH)D concentrations were not different in NW or OB individuals (NW-IS compared with OB-IS).

Simulation-based training is superior to problem-based learning for the acquisition of critical assessment and management skills.

OBJECTIVE: To determine whether full-scale simulation (SIM) is superior to interactive problem-based learning (PBL) for teaching medical students acute care assessment and management skills. DESIGN: Randomized controlled trial. SETTING: Simulation center at a U.S. medical school. SUBJECTS: Thirty-one fourth-year medical students in a week-long acute care course. INTERVENTIONS: After institutional review board approval and informed consent, eligible students were randomized to either the SIM or PBL group. On day 1, all subjects underwent a simulator-based initial assessment designed to evaluate their critical care skills. Two blinded investigators assessed each student using a standardized checklist. Subsequently, the PBL group learned about dyspnea in a standard PBL format. The SIM group learned about dyspnea using the simulator. To equalize simulator education time, the PBL group learned about acute abdominal pain on the simulator, whereas the SIM group used the PBL format. On day 5, each student was tested on a unique dyspnea scenario. MEASUREMENTS AND MAIN RESULTS: Mean initial assessment and final assessment checklist scores and their change for the SIM and PBL groups were compared using the Student's t-test. A p < .05 was considered significant. The SIM and PBL groups had similar mean (PBL 0.44, SIM 0.47, p = .64) initial assessment scores (earned score divided by maximum score) and were deemed equivalent. The SIM group performed better than the PBL group on the final assessment (mean, PBL 0.53, SIM 0.72, p < .0001). When each student's change in score (percent correct on final assessment minus percent correct on the initial assessment) was compared, SIM group students performed better (mean improvement, SIM 25 percentage points vs. PBL 8 percentage points, p < .04) CONCLUSIONS: For fourth-year medical students, simulation-based learning was superior to problem-based learning for the acquisition of critical assessment and management skills.