Childhood cancer and later development of the metabolic syndrome

The improving survival rate of patients with childhood cancer has led to a growing awareness of the long-term effects of malignant disease and its treatment. Various endocrine abnormalities have been reported as frequent long-term adverse effects of cancer treatment in childhood, and among these growth hormone (GH) deficiency is the most common one, especially after cranial irradiation. Besides promoting growth, GH has well-established metabolic effects. Patients with GH deficiency tend to be obese, and obesity per se is also associated with insulin resistance which plays a key role in a cluster of metabolic derangements including glucose intolerance, hypertension, lipid abnormalities and atherosclerotic cardiovascular disease. This condition is known as the metabolic syndrome. Our recent observations indicate that a combination of obesity, glucose intolerance, hyperinsulinaemia and an abnormal lipid profile can be observed in long-term survivors of childhood cancer. Every sixth patient had the triad of obesity, hyperinsulinaemia and low HDL cholesterol, whereas this combination was not seen in any of the controls. The survivors with such a high-risk profile for cardiovascular disease had markedly reduced spontaneous GH secretion, and also additional features of the metabolic syndrome, such as higher systolic blood pressure and higher plasma glucose and serum triglyceride levels. Accordingly, decreased GH secretion, or alternatively some other disturbance in the hypothalamic-pituitary axis, emerging as a consequence of cranial radiation, may expose long-term survivors of childhood cancer to premature evolution of the metabolic syndrome. This can have an important impact on the long-term prognosis in these patients, because the syndrome as such results in an increased risk of cardiovascular morbidity and mortality.