Polycystic ovary syndrome (PCOS) is the most common ovarian disorder associated with androgen excess in women, which justifies the growing interest of endocrinologists. Great efforts have been made in the last 2 decades to define the syndrome. The presence of three different definitions for the diagnosis of PCOS reflects the phenotypic heterogeneity of the syndrome. Major criteria are required for the diagnosis, which in turn identifies different phenotypes according to the combination of different criteria. In addition, the relevant impact of metabolic issues, specifically insulin resistance and obesity, on the pathogenesis of PCOS, and the susceptibility to develop earlier than expected glucose intolerance states, including type 2 diabetes, has supported the notion that these aspects should be considered when defining the PCOS phenotype and planning potential therapeutic strategies in an affected subject. This paper offers a critical endocrine and European perspective on the debate on the definition of PCOS and summarises all major aspects related to aetiological factors, including early life events, potentially involved in the development of the disorder. Diagnostic tools of PCOS are also discussed, with emphasis on the laboratory evaluation of androgens and other potential biomarkers of ovarian and metabolic dysfunctions. We have also paid specific attention to the role of obesity, sleep disorders and neuropsychological aspects of PCOS and on the relevant pathogenetic aspects of cardiovascular risk factors. In addition, we have discussed how to target treatment choices based according to the phenotype and individual patient's needs. Finally, we have suggested potential areas of translational and clinical research for the future with specific emphasis on hormonal and metabolic aspects of PCOS.

The objective of the study was the comparison of anti-Müllerian hormone (AMH) levels among obese or overweight and normal-weight women with the four different polycystic ovary syndrome (PCOS) phenotypes and healthy control subjects. AMH levels were evaluated in four age- and body mass index (BMI)-matched groups of 25 normal-weight and 25 obese or overweight women each, belonging to the four main subsets of the syndrome resulting from combinations of the three diagnostic criteria [ group 1: oligo- and/or anovulation (ANOV), hyperandrogenemia (HA), and polycystic ovaries (PCO) on ultrasonographic evaluation; group 2: ANOV and HA; group 3: HA and PCO, group 4: ANOV and PCO], and in 50 (25 obese or overweight and 25 normal weight) age- and BMI-matched healthy control subjects. Age, BMI, waist circumference, FSH, LH, prolactin, testosterone, Δ₄-androstenedione, dehydroepiandrosterone-sulfate, 17α-OH-progesterone, fasting insulin, glucose, AMH, free androgen index, and homeostasis model assessment for insulin resistance index were analyzed. AMH levels were significantly higher in PCOS groups 1 and 2 compared with groups 3 and 4 and the control group and higher in PCOS groups 3 and 4 compared with the control group. AMH levels were significantly increased in normal-weight compared with obese and overweight women. AMH concentrations were independently predicted, in order of significance, by LH and testosterone levels, BMI (negatively), and the total number of follicles 2–9 mm in diameter. The differences in circulating AMH levels between the main phenotypic groups of PCOS women appear to reflect the severity of the syndrome, but are negatively affected by obesity. Increased LH levels might be the most significant independent link between PCOS-associated disorders of ovulation and the observed increase in circulating AMH concentration.

Polycystic ovary syndrome (PCOS) is a heterogeneous disorder characterized by oligo- or anovulation (ANOV), biochemical or clinical manifestations of hyperandrogenemia (HA) and PCOs. Four phenotypes of PCOS exist [phenotype 1 (ANOV + HA + PCO), phenotype 2 (ANOV + HA), phenotype 3 (HA + PCO) and phenotype 4 (ANOV + PCO)] but the differences between them are not well studied. We compared markers of insulin resistance (IR) and endocrine characteristics between the different PCOS phenotypes. We prospectively studied 1212 consecutive women with PCOS and 254 BMI-matched healthy women. Phenotypes 1-4 were present in 48.2, 30.7, 9.7 and 11.4% of patients, respectively. BMI did not differ between the four phenotypes and controls. Both normal weight and overweight/obese women with phenotypes 1 and 2 were more insulin resistant than controls. Overweight/obese, but not normal weight, women with phenotype 4 were more insulin resistant than controls, while IR in women with phenotype 3 did not differ from controls regardless of obesity. In normal weight subjects, women with phenotypes 1 and 2 were more insulin resistant than women with phenotype 4. In overweight/obese subjects, women with phenotype 1 were more insulin resistant than women with phenotypes 2 and 3 and women with phenotype 4 were more insulin resistant than those with phenotype 3. Circulating androgens were higher in normal weight and overweight/obese PCOS patients with phenotypes 1-3 compared with those with phenotype 4, and higher in normal weight PCOS patients with phenotype 1 than in those with phenotype 2. Phenotype 1 is associated with more IR and more pronounced HA than phenotype 2. Phenotypes 2 and 4 with obesity, are also characterized by IR. In contrast, phenotype 3 is not associated with IR.

Polycystic ovary syndrome (PCOS) is a common metabolic and reproductive disorder in women. An increased cardiovascular risk has to be anticipated in PCOS as it is a metabolically unstable condition. Among cardiovascular risk factors, dyslipidemia is certainly the most persistent and highly prevalent. Predominant observation is an elevation of LDL cholesterol in all PCOS patients. Decreased concentrations of HDL cholesterol are found in obese PCOS from the third decade of life onwards while triglycerides start to rise from the second decade of life. PCOS is associated with oxidative stress, namely increased production of free radicals followed by decreased serum antioxidant levels and antioxidant enzyme activity. Broad range of endocrine and metabolic disturbances like obesity, hyperinsulinemia as well as dyslipidemia might be responsible for PCOS-associated oxidative stress. Therapeutic interventions in PCOS women based on lifestyle modification as well as use of insulin sensitizers did not show significant effect on dyslipidemia. Statins are considered to be a group of promising agents that are safe and effective in improving total cholesterol, LDL cholesterol and triglycerides, and possess antioxidant activity. Supplementation with omega-3 fatty acids, α-lipoic acid and N-acetylcysteine is considered to have an anti-inflammatory and antioxidant effect and to improve dyslipidemia and insulin sensitivity in PCOS women.

The central mechanism involved in the pathogenesis of MAFLD is insulin resistance with hyperinsulinemia, which stimulates triglyceride synthesis and accumulation in the liver. On the other side, triglyceride and free fatty acid accumulation in hepatocytes promotes insulin resistance via oxidative stress, endoplasmic reticulum stress, lipotoxicity, and the increased secretion of hepatokines. Cytokines and adipokines cause insulin resistance, thus promoting lipolysis in adipose tissue and ectopic fat deposition in the muscles and liver. Free fatty acids along with cytokines and adipokines contribute to insulin resistance in the liver via the activation of numerous signaling pathways. The secretion of hepatokines, hormone-like proteins, primarily by hepatocytes is disturbed and impairs signaling pathways, causing metabolic dysregulation in the liver. ER stress and unfolded protein response play significant roles in insulin resistance aggravation through the activation of apoptosis, inflammatory response, and insulin signaling impairment mediated via IRE1/PERK/ATF6 signaling pathways and the upregulation of SREBP 1c. Circadian rhythm derangement and biological clock desynchronization are related to metabolic disorders, insulin resistance, and NAFLD, suggesting clock genes as a potential target for new therapeutic strategies. This review aims to summarize the mechanisms of hepatic insulin resistance involved in NAFLD development and progression.