^ Alberti KG, Eckel RH, Grundy SM, Zimmet PZ, Cleeman JI, Donato KA, Fruchart JC, James WP, Loria CM, Smith SC (October 2009). "Harmonizing the metabolic syndrome: a joint interim statement of the International Diabetes Federation Task Force on Epidemiology and Prevention; National Heart, Lung, and Blood Institute; American Heart Association; World Heart Federation; International Atherosclerosis Society; and International Association for the Study of Obesity" (PDF). Circulation. 120 (16): 1640–45. doi:10.1161/CIRCULATIONAHA.109.192644. PMID 19805654.
Another method is to have the individual wear a device that monitors and records the blood pressure at regular intervals during the day to evaluate blood pressure over time. This is especially helpful during the diagnostic process and can help rule out "white coat" hypertension, the high measurements that are sometimes present only when the person is in the doctor's office and not at other times. (See High Blood Pressure: Using an Ambulatory Blood Pressure Monitor on FamilyDoctor.org.)
The exact cause of metabolic syndrome is not known. Many features of the metabolic syndrome are associated with "insulin resistance." Insulin resistance means that the body does not use insulin efficiently to lower glucose and triglyceride levels. Insulin resistance is a combination of genetic and lifestyle factors. Lifestyle factors include diet, activity and perhaps interrupted sleep patterns (such as sleep apnea).
Aronow WS, Fleg JL, Pepine CJ, Artinian NT, Bakris G, Brown AS, et al. ACCF/AHA 2011 expert consensus document on hypertension in the elderly: a report of the American College of Cardiology Foundation Task Force on Clinical Expert Consensus documents developed in collaboration with the American Academy of Neurology, American Geriatrics Society, American Society for Preventive Cardiology, American Society of Hypertension, American Society of Nephrology, Association of Black Cardiologists, and European Society of Hypertension. J Am Coll Cardiol. 2011 May 17. 57(20):2037-114. [Medline].
The previous definitions of the metabolic syndrome by the International Diabetes Federation and the revised National Cholesterol Education Program are very similar and they identify individuals with a given set of symptoms as having metabolic syndrome. There are two differences, however: the IDF definition states that if body mass index (BMI) is greater than 30 kg/m2, central obesity can be assumed, and waist circumference does not need to be measured. However, this potentially excludes any subject without increased waist circumference if BMI is less than 30. Conversely, the NCEP definition indicates that metabolic syndrome can be diagnosed based on other criteria. Also, the IDF uses geography-specific cut points for waist circumference, while NCEP uses only one set of cut points for waist circumference regardless of geography. These two definitions are much more similar than the original NCEP and WHO definitions.
^ Saiz, Luis Carlos; Gorricho, Javier; Garjón, Javier; Celaya, Mª Concepción; Muruzábal, Lourdes; Malón, Mª del Mar; Montoya, Rodolfo; López, Antonio (2017-10-11). "Blood pressure targets for the treatment of people with hypertension and cardiovascular disease". Cochrane Database of Systematic Reviews. 10: CD010315. doi:10.1002/14651858.cd010315.pub2. PMID 29020435.
^ Qaseem A, Wilt TJ, Rich R, Humphrey LL, Frost J, Forciea MA (17 January 2017). "Pharmacologic Treatment of Hypertension in Adults Aged 60 Years or Older to Higher Versus Lower Blood Pressure Targets: A Clinical Practice Guideline From the American College of Physicians and the American Academy of Family Physicians". Annals of Internal Medicine. 166 (6): 430–437. doi:10.7326/M16-1785. PMID 28135725.
Insulin serves as a “key” to open your cells, to allow the glucose to enter -- and allow you to use the glucose for energy. Without insulin, there is no “key.” So, the sugar stays -- and builds up-- in the blood. The result: the body’s cells starve from the lack of glucose. And, if left untreated, the high level of “blood sugar” can damage eyes, kidneys, nerves, and the heart, and can also lead to coma and death.
^ Vancampfort D, Correll CU, Wampers M, Sienaert P, Mitchell AJ, De Herdt A, Probst M, Scheewe TW, De Hert M (July 2014). "Metabolic syndrome and metabolic abnormalities in patients with major depressive disorder: a meta-analysis of prevalences and moderating variables". Psychological Medicine. 44 (10): 2017–28. doi:10.1017/S0033291713002778. PMID 24262678.
This explains why my attempts at a low fat, high protein, high carb diet left me gaining weight all while eating 1000 calories per day! Those 1000 calories were simply fueling my brain and then getting shuttled into my fat cells. If you are not insulin resistant, then this diet may be just the thing you need to shed some short term pounds (although I never recommend a 1000 calorie diet!- more on that later), but to me it caused metabolic chaos.
Bhasin et al, as part of the Framingham Heart Study, found that sex hormone-binding globulin is independently associated with the risk of metabolic syndrome, whereas testosterone is not. Age, body mass index (BMI), and insulin sensitivity independently affect sex hormone-binding globulin and testosterone levels.  More recent studies have raised the possibility of an association between testosterone deficiency and metabolic syndrome. 
^ Ostchega Y, Dillon CF, Hughes JP, Carroll M, Yoon S (July 2007). "Trends in hypertension prevalence, awareness, treatment, and control in older U.S. adults: data from the National Health and Nutrition Examination Survey 1988 to 2004". Journal of the American Geriatrics Society. 55 (7): 1056–65. doi:10.1111/j.1532-5415.2007.01215.x. PMID 17608879.
Especially severe cases of hypertension, or hypertensive crises, are defined as a BP of more than 180/120 mm Hg and may be further categorized as hypertensive emergencies or urgencies. Hypertensive emergencies are characterized by evidence of impending or progressive target organ dysfunction, whereas hypertensive urgencies are those situations without progressive target organ dysfunction. 
Low blood sugar (hypoglycemia) is common in people with type 1 and type 2 DM. Most cases are mild and are not considered medical emergencies. Effects can range from feelings of unease, sweating, trembling, and increased appetite in mild cases to more serious effects such as confusion, changes in behavior such as aggressiveness, seizures, unconsciousness, and (rarely) permanent brain damage or death in severe cases. Moderately low blood sugar may easily be mistaken for drunkenness; rapid breathing and sweating, cold, pale skin are characteristic of low blood sugar but not definitive. Mild to moderate cases are self-treated by eating or drinking something high in sugar. Severe cases can lead to unconsciousness and must be treated with intravenous glucose or injections with glucagon.
Metabolic syndrome is a cluster of metabolic risk factors that come together in a single individual. These metabolic factors include insulin resistance, hypertension (high blood pressure), cholesterol abnormalities, and an increased risk for blood clotting. Affected individuals are most often overweight or obese. An association between certain metabolic disorders and cardiovascular disease has been known since the 1940s.