While it is known that vitamin D deficiency is associated with adverse bone outcomes, it remains unclear whether low vitamin D status may increase the risk of a wider range of health outcomes. We had the opportunity to explore the association between common genetic variants associated with both 25 hydroxyvitamin D (25OHD) and the vitamin D binding protein (DBP, encoded by the GC gene) with a comprehensive range of health disorders and laboratory tests in a large academic medical center. We used summary statistics for 25OHD and DBP to generate polygenic scores (PGS) for 66,482 participants with primarily European ancestry and 13,285 participants with primarily African ancestry from the Vanderbilt University Medical Center Biobank (BioVU). We examined the predictive properties of PGS25OHD, and two scores related to DBP concentration with respect to 1322 health-related phenotypes and 315 laboratory-measured phenotypes from electronic health records. In those with European ancestry: (a) the PGS25OHD and PGSDBP scores, and individual SNPs rs4588 and rs7041 were associated with both 25OHD concentration and 1,25 dihydroxyvitamin D concentrations; (b) higher PGS25OHD was associated with decreased concentrations of triglycerides and cholesterol, and reduced risks of vitamin D deficiency, disorders of lipid metabolism, and diabetes. In general, the findings for the African ancestry group were consistent with findings from the European ancestry analyses. Our study confirms the utility of PGS and two key variants within the GC gene (rs4588 and rs7041) to predict the risk of vitamin D deficiency in clinical settings and highlights the shared biology between vitamin D-related genetic pathways a range of health outcomes.

Gestational diabetes mellitus (GDM) is a frequent complication of pregnancy. The specific mechanisms underlying GDM have not yet been fully elucidated. Contemporary research indicates a potential association between liver enzyme irregularities and an increased risk of metabolic disorders, including diabetes. The alanine aminotransferase (ALT) level is recognized as a sensitive marker of liver injury. An increase in ALT levels is hypothesized to be linked to the pathogenesis of insulin resistance and diabetes. Nonetheless, the definitive causal link between ALT levels and GDM still needs to be determined. This investigation utilized two-sample Mendelian randomization (MR) to examine the genetic causation between alanine aminotransferase (ALT) and GDM. We acquired alanine aminotransferase (ALT)-related GWAS summary data from the UK Biobank, Million Veteran Program, Rotterdam Study, and Lifeline Study. Gestational diabetes data were obtained from the FinnGen Consortium. We employed various MR analysis techniques, including inverse-variance weighted (IVW), MR Egger, weighted median, simple, and weighted weighting. In addition to MR-Egger intercepts, Cochrane’s Q test was also used to assess heterogeneity in the MR data, and the MR-PRESSO test was used to assess horizontal pleiotropy. To assess the association’s sensitivity, a leave-one-out approach was employed. The IVW results confirmed the independent risk factor for GDM development, as indicated by the ALT level (p = .011). As shown by leave-one-out analysis, horizontal pleiotrophy did not significantly skew the causative link (p > .05). Our dual-sample MR analysis provides substantiated evidence of a genetic causal relationship between alanine aminotransferase (ALT) levels and gestational diabetes.

TwinsMX registry is a national research initiative in Mexico that aims to understand the complex interplay between genetics and environment in shaping physical and mental health traits among the country’s population. With a multidisciplinary approach, TwinsMX aims to advance our knowledge of the genetic and environmental mechanisms underlying ethnic variations in complex traits and diseases, including behavioral, psychometric, anthropometric, metabolic, cardiovascular and mental disorders. With information gathered from over 2800 twins, this article updates the prevalence of several complex traits; and describes the advances and novel ideas we have implemented such as magnetic resonance imaging. The future expansion of the TwinsMX registry will enhance our comprehension of the intricate interplay between genetics and environment in shaping health and disease in the Mexican population. Overall, this report describes the progress in the building of a solid database that will allow the study of complex traits in the Mexican population, valuable not only for our consortium, but also for the worldwide scientific community, by providing new insights of understudied genetically admixed populations.

Women with twin pregnancies experience greater sleep disturbance compared to women with singleton pregnancies. The aims of this study were to explore the sleep quality in women with twin pregnancies and to compare their sleep dimensions with coetaneous single pregnancies. This was an observational study in which women were enrolled at the end of pregnancy in the Obstetric Service of Hospital La Paz (Spain). The women were classified as single (n = 143) or twin pregnancy (n = 62). Pregnant women responded to the Pittsburgh Sleep Quality Index to evaluate sleep quality, latency, duration, efficiency, perturbance, use of medication, and daytime dysfunction. The higher the index, the greater the alteration of sleep quality. Without statistical differences, a poor sleep quality was higher in women with single (66.7%) than women with twin pregnancies (22.8%). The good sleeper slept 6.8 h/day in single pregnancy and 7.3 h/day in twin pregnancy. The sleep perturbation and dysfunctionality were higher in women with twin than single pregnancies. The use of medication to sleep was significantly lower in women with twin than single pregnancies. In women with twin pregnancy, the body weight gain during first trimester had a positive correlation with worse sleep quality and sleep perturbations. Twin pregnancy needed more than 7 h/day to have a high sleep quality, showing greater sleep perturbations and daytime dysfunction than single pregnancies. The control of gestational body weight can improve the sleep quality, disturbances, and duration in twin gestations. Sleep screening during pregnancy would be necessary to handle sleep issues and increase benefits in twin gestational outcomes.

The current study was motivated by an interest in deepening understanding of Brazilian twin research, which is underrepresented internationally, in an effort to rectify this situation. Our aim was threefold: (1) to carry out a comprehensive investigation of Brazilian research on twins according to the area of knowledge; (2) to evaluate the representation of research in the field of psychology in comparison with other areas; (3) to evaluate characteristics of the research that may have contributed to its exclusion from the comprehensive meta-analysis of 50 years of twin research. A scoping review was performed according to PRISMA guidelines. Titles and abstracts were searched up to 2022 in six databases: CAPES, BDLTD, PePSIC, PubMed, Google Scholar, and SciELO, using selected keywords both in Portuguese and in English (e.g., ‘twins’ and ‘Brazil’; ‘twinning’ and ‘Brazil’; ‘gemelaridade’ [twinning], and ‘gêmeos’ [twins]). Three hundred and forty publications were included in the review. Approximately half (53.8‰) used the classic twin design to investigate the heritability of several traits, and the other half (46.2%) used other research designs. The scoping review showed that the number of publications doubled approximately every 10 years. Most publications were from the health area, with medicine accounting for approximately half of the studies, followed by psychology, odontology, and biology. We found that the interest in studying twins among Brazilian scientists is increasing over the years and there are reasons to be enthusiastic about the potential impact of this trend in the global scenario.

Between 2006 and 2021, the Hungarian Twin Registry (HTR) operated a volunteer twin registry of all age groups (50% monozygotic [MZ], 50% dizygotic [DZ], 70% female, average age 34 ± 22 years), including 1044 twin pairs, 24 triplets and one quadruplet set. In 2021, the HTR transformed from a volunteer registry into a population-based one, and it was established in the Medical Imaging Centre of Semmelweis University in Budapest. Semmelweis University’s innovation fund supported the development of information technology, a phone bank and voicemail infrastructure, administrative materials, and a new website was established where twins and their relatives (parent, foster parent or caregiver) can register. The HTR’s biobank was also established: 157,751 individuals with a likely twin-sibling living in Hungary (77,042 twins, 1194 triplets, 20 quadruplets, and one quintuplet) were contacted between February and March of 2021 via sealed letters. Until November 20, 2022, 12,001 twin individuals and their parents or guardians (6724 adult twins, 3009 parents/guardians and 5277 minor twins) registered, mostly online. Based on simple self-reports, 37.6% of the registered adults were MZ twins and 56.8% were DZ; 1.12% were triplets and 4.5% were unidentified. Of the registered children, 22.3% were MZ, 72.7% were DZ, 1.93% were triplets, and 3.05% were unidentified. Of the registered twins, 59.9% were female (including both the adult and minor twins). The registration questionnaire consists of eight parts, including socio-demographic and anthropometric data, smoking habits and medical questions (diseases, operations, therapies). Hungary’s twin registry has become the sole and largest population-based twin registry in Central Eastern Europe. This new resource will facilitate performing world-class modern genetic research.

This Position Statement provides guidelines for health professionals who work with individuals and families seeking predictive genetic testing and laboratory staff conducting the tests. It presents the major practical, psychosocial and ethical considerations associated with presymptomatic and predictive genetic testing in adults who have the capacity to make a decision, children and young people who lack capacity, and adults living with reduced or fluctuating cognitive capacity.

Predictive Testing Recommendations: (1) Predictive testing in adults, young people and children should only be offered with pretest genetic counseling, and the option of post-test genetic counseling. (2) An individual considering whether to have a predictive test should be supported to make an autonomous and informed decision. Regarding Children and Young People: (1) Predictive testing should only be offered to children and young people for conditions where there is likely to be a direct medical benefit to them through surveillance, use of prevention strategies, or other medical interventions in the immediate future. (2) Where symptoms are likely to develop in childhood, in the absence of direct medical benefit from this knowledge, genetic health professionals and parents/guardians should discuss whether undertaking predictive testing is the best course of action for the child and the family as a whole. (3) Where symptoms are likely to develop in adulthood, the default position should be to postpone predictive testing until the young person achieves the capacity to make an autonomous and informed decision. This is applicable regardless of whether there is some action that can be taken in adulthood.

A review of an unusual twin type—twins born to women with two uteri (uterus didelphys)—is presented. This review is followed by summaries of recent research and perspectives concerning prenatal aneuploidy screening for twin pregnancies, twin conceptions by same-sex male couples, legal personality of conjoined twins, and a twin study of cannabis use. Interesting information about twins that has appeared in the media is also presented, namely how being taken for twins saved a pair of sisters; twin children of a jailed Nobel Prize winner, British ‘biracial’ twins, triplets born at the start of Russia’s attack on Ukraine, and twins born in different years.