The metabolic syndrome: Growing challenge in primary care

DR. MILLER is assistant professor, division of pediatric endocrinology,University of Florida College of Medicine, Gainesville.DR. SILVERSTEIN is professor of pediatrics, University of FloridaCollege of Medicine, Gainesville.They have nothing to disclose in regard to affiliations with, or financialinterests in, any organization that may have an interest in any part ofthis article.

Childhood obesity is epidemic, with children becoming obese at younger ages. Data from the International Obesity Task Force indicates that more than 22 million children under 5 years of age are overweight or obese.¹ As the incidence of childhood obesity has increased, so have the consequences, including obstructive sleep apnea, orthopedic problems, hyperandrogenism, hyperinsulinism, impaired glucose tolerance, and cardiovascular disease.²

These conditions persist into adulthood, increasing both the medical burden on society and the risk of early morbidity and mortality in those affected. Just as preventing obesity in childhood is critical, so is early identification and treatment of comorbidities in children with established obesity to forestall the consequences of those conditions.

Gender and ethnic differences

The metabolic syndrome is more prevalent in males than females worldwide.¹⁰ The prevalence in females has markedly increased over the past decade, however. Females have 26% more subcutaneous fat than males, even when matched for BMI. This gender difference is observed as early as the first year of life.¹¹ However, the "male" pattern of accumulation of body fat-predominantly in the upper body with visceral rather than subcutaneous distribution-is strongly associated with development of the metabolic syndrome.

Visceral fat is the metabolically active fat, producing adipokines, which increase insulin resistance. Insulin resistance is closely related to the amount of visceral fat deposition and is poorly correlated with BMI.¹² Waist circumference-often measured at the level of the umbilicus or the top of the iliac crest with the patient standing-or waist-to-hip ratio (the ratio of waist circumference to hip circumference measured at the iliac crest) correlates well with insulin resistance and the metabolic syndrome.¹³

In North America, the metabolic syndrome disproportionately affects African Americans, Mexican Americans, and Native Americans.¹⁴ African Americans are 1.4 to 2.2 times more likely than Caucasians to have type 2 diabetes; the prevalence of type 2 diabetes in Native Americans is 2.8 times the overall rate.¹⁵ African Americans have lower resting energy expenditure¹⁶ and lower insulin sensitivity than Caucasians matched for age, sex, and BMI.¹⁷ They also exhibit insulin hypersecretion in response to an oral glucose load,¹⁸ which increases their risk of developing type 2 diabetes.

Cardiovascular risks

The major long-term complication associated with the metabolic syndrome is cardiovascular disease. The cardiovascular risks conferred by the syndrome include dyslipidemia, hypertension, a procoagulable state, and glucose intolerance and type 2 diabetes.