Vitamin D and cardiometabolic risk factors and diseases.

Obesity, type 2 diabetes, and cardiovascular disease (CVD) are the most common preventable causes of morbidity and mortality worldwide. Insulin resistance, which is a shared feature in these conditions, is also strongly linked to the development of polycystic ovary syndrome (PCOS), which is the most common endocrine disease in women of reproductive age and a major cause of infertility. Vitamin D deficiency has reached epidemic proportions worldwide, primarily due to the shift to sedentary, indoor lifestyles and sun avoidance behaviours to protect against skin cancer. In recent years, vitamin D deficiency has been implicated in the aetiology of type 2 diabetes, PCOS and CVD, and has been shown to be associated with their risk factors including obesity, insulin resistance, hypertension, as well as chronic low-grade inflammation. Treating vitamin D deficiency may offer a feasible and cost-effective means of reducing cardiometabolic risk factors at a population level in order to prevent the development of type 2 diabetes and CVD. However, not all intervention studies show that vitamin D supplementation alleviates these risk factors. Importantly, there is significant heterogeneity in existing studies with regards to doses and drug regimens used, populations studied (i.e. vitamin D deficient or sufficient), and the lengths of supplementation, and only few studies have directly examined the effect of vitamin D on insulin secretion and resistance with the use of clamp methods. Therefore, there is a need for well-designed large scale trials to clarify the role of vitamin D supplementation in the prevention of type 2 diabetes, PCOS, and CVD.

Obesity and polycystic ovary syndrome.

Obesity is now a major international health concern. It is increasingly common in young women with reproductive, metabolic and psychological health impacts. Reproductive health impacts are often poorly appreciated and include polycystic ovary syndrome (PCOS), infertility and pregnancy complications. PCOS is the most common endocrine condition in women and is underpinned by hormonal disturbances including insulin resistance and hyperandrogenism. Obesity exacerbates hormonal and clinical features of PCOS and women with PCOS appear at higher risk of obesity, with multiple underlying mechanisms linking the conditions. Lifestyle intervention is first line in management of PCOS to both prevent weight gain and induce weight loss; however improved engagement and sustainability remain challenges with the need for more research. Medications like metformin, orlistat, GLP1 agonists and bariatric surgery have been used with the need for large scale randomised clinical trials to define their roles.