Obesity and type 2 diabetes mellitus (T2DM) are global epidemics at the present time, being a serious public health issue. An increased prevalence in the number of obese people promotes a risk for developing cardiovascular diseases (CVD) and some types of cancer. The ErbB signaling pathway plays a significant role in development of the disorders associated with metabolic dysfunction (e.g., T2DM, obesity, arterial hypertension). Neuregulin 4 (NRG4) is a new adipokine with similar effects to adiponectin. Interaction between the ErbB3, ErbB4 receptors and their ligand, NRG4, launches the processes required to maintain the energy balance in the cells. There are controversial literature data on NRG4 levels in blood circulation. In particular, the existing data concerning functions / mechanism of NRG4 action has been obtained in experimental animals and cell lines, which is not always reproducible in humans. According to some works, liver may be the key target organ for NRG4. The present article is devoted to assessment of relationships between the NRG4 level in blood, and the parameters of carbohydrate and lipid metabolism, as well as presence of diseases associated with obesity. The study included obese patients with and without type 2 diabetes. The content of NRG4, indices of carbohydrate and lipid metabolism in the blood was assessed by means of enzyme immunoassay and biochemical techniques, respectively. It was found that the level of NRG4 was increased in obese patients with T2DM compared with healthy donors, and obese patients without T2DM. Statistical evaluation by correlation and regression analysis revealed numerous relationships between NRG4 and the parameters of lipid and carbohydrate metabolism, as well as some correlations between the NRG4 levels and clinical disorders associated with obesity (type 2 diabetes and arterial hypertension). Thus, NRG4 may be involved into the development of dyslipidemia in obese patients. We consider an increase of blood NRG4 levels in obese patients with type 2 diabetes as a compensatory response to the increased insulin-mediated lipogenesis. The data obtained are important in search for new points of influence upon pathogenesis of diseases associated with metabolic disorders. Neuroregulin 4 and its receptors may be promising targets for the treatment of socially significant clinical disorders.