**13. Metabolic syndrome (MetS) as the post-reproductive stage of ontogenesis**

Long time ago physicians noticed that many patients have common features of external appearances and biochemical indices of abnormal metabolism, which included insulin resistance, obesity, atherogenic dyslipidemia and hypertension. By the end of 80s of the 20th century the term "Metabolic syndrome" has been accepted and its own diagnostic code: 277.7 has been assigned by the International Classification, 9th Division, Clinical Modification (ICD-9-CM). However, the current definitions of the metabolic syndrome (MetS) give no clues to the essence of MetS and are mostly just listings of symptoms, for example: "The metabolic syndrome is a constellation of metabolic disorders including obesity, hypertension, and insulin resistance, components, which are risk factors for the development of diabetes, hypertension, cardiovascular, and renal disease" [123, 124]. This "clustering" or "constellation" of risk factors were considered to share underlying causes, mechanisms and features. The diagnosis of MetS is accepted only when at least three out of five symptoms are present in a patient [125, 126]. It was early recognized that people with isolated components, but who do not fit the definition of metabolic syndrome, are not at as high a risk for type 2 diabetes (T2D) or cardiovascular diseases (CVD). For example, people with isolated hypertension or isolated hyperlipidemia are at risk of CVD, or people with isolated obesity are at risk for T2D, but less so than people who meet multiple criteria of MetS [123].

It was expected that a comprehensive definition for the metabolic syndrome and its key features will facilitate research into its causes and lead to pharmacologic and lifestyle treatment approaches [127]. However, analysis of the tremendous amount of publications regarding MetS revealed that more than 30 years after defining MetS, there is still no deep understanding how and why MetS develops. Much of the literature can be roughly divided into supporters and opponents of considering insulin resistance as the primary symptom for the diagnosing MetS [123, 128–130]. These discrepancies were reflected in the criteria for diagnosing MetS provided by several Institutions, which were thoroughly reviewed in [123]. The discussions become heated by publications that ethnic and racial factors may greatly affect the criteria for diagnosis of MetS [127, 131].
