Cushing's syndrome is a serious endocrine disease caused by chronic, autonomous, and excessive secretion of cortisol. The syndrome is associated with increased mortality and impaired quality of life because of the occurrence of comorbidities. These clinical complications include metabolic syndrome, consisting of systemic arterial hypertension, visceral obesity, impairment of glucose metabolism, and dyslipidaemia; musculoskeletal disorders, such as myopathy, osteoporosis, and skeletal fractures; neuropsychiatric disorders, such as impairment of cognitive function, depression, or mania; impairment of reproductive and sexual function; and dermatological manifestations, mainly represented by acne, hirsutism, and alopecia. Hypertension in patients with Cushing's syndrome has a multifactorial pathogenesis and contributes to the increased risk for myocardial infarction, cardiac failure, or stroke, which are the most common causes of death; risks of these outcomes are exacerbated by a prothrombotic diathesis and hypokalaemia. Neuropsychiatric disorders can be responsible for suicide. Immune disorders are common; immunosuppression during active disease causes susceptibility to infections, possibly complicated by sepsis, an important cause of death, whereas immune rebound after disease remission can exacerbate underlying autoimmune diseases. Prompt treatment of cortisol excess and specific treatments of comorbidities are crucial to prevent serious clinical complications and reduce the mortality associated with Cushing's syndrome.

Cardiovascular accidents represent the most important cause of death in patients with Cushing's syndrome. This prospective study aims at evaluating carotid arteries by echo-Doppler ultrasonography and clinical and metabolic markers of atherosclerosis in 25 patients with Cushing's disease (CD) before and after 1 yr of remission. Thirty-two sex- and age-matched subjects (control-1) and 32 body mass index-matched subjects (control-2) served as controls. At diagnosis, CD patients had higher body mass index, waist to hip ratio (WHR), total, low-density lipoprotein-cholesterol and total/high-density lipoprotein (HDL) ratio, glucose and insulin, as well as lower HDL-cholesterol than control-1; they had higher WHR and total/HDL ratio and lower HDL-cholesterol than control-2. They also had higher intima-media thickness (IMT), and lower systolic lumen diameter and distensibility coefficient (DC) than either control group. Atherosclerotic plaques were detected in 31.2% of patients, 0 control-1, and 6.2% of control-2 subjects. One year after remission, WHR, LDL-cholesterol, and IMT significantly decreased, whereas systolic lumen diameter and DC significantly increased. However, all of the above parameters were still abnormal compared with control-1, but not control-2. A significant correlation was found between WHR, glucose and insulin levels, and right and left carotid IMT. WHR was the best predictor of left IMT and left DC in active, but not in cured, patients. The duration of hypercortisolism was the best predictor of right DC in active but not in cured patients. In conclusion, patients with CD have severe atherosclerotic damage. The persistence of a metabolic syndrome, vascular damage, and atherosclerotic plaques after cortisol level normalization makes these subjects still at high cardiovascular risk despite disease remission.

The results of this study demonstrated that cabergoline treatment is effective in controlling cortisol secretion for at least 1-2 yr in more than one third of a limited population of patients with CD. If this evidence is confirmed by additional studies, this agent may be considered as a useful treatment option in patients with CD who are unsuccessfully treated by neurosurgery.

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Cushing’s syndrome is commonly complicated with an impairment of glucose metabolism, which is often clinically manifested as diabetes mellitus. The development of diabetes mellitus in Cushing’s syndrome is both a direct and indirect consequence of glucocorticoid excess. Indeed, glucocorticoid excess induces a stimulation of gluconeogenesis in the liver as well as an inhibition of insulin sensitivity both in the liver and in the skeletal muscles, which represent the most important sites responsible for glucose metabolism. In particular, glucocorticoid excess stimulates the expression of several key enzymes involved in the process of gluconeogenesis, with a consequent increase of glucose production, and induces an impairment of insulin sensitivity either directly by interfering with the insulin receptor signaling pathway or indirectly, through the stimulation of lipolysis and proteolysis and the consequent increase of fatty acids and amino acids, which contribute to the development of insulin resistance. Moreover, the peculiar distribution of adipose tissue throughout the body, with the predominance of visceral adipose tissue, significantly contributes to the worsening of insulin resistance and the development of a metabolic syndrome, which participates in the occurrence and maintenance of the impairment of glucose tolerance. Finally, glucocorticoid excess is able to impair insulin secretion as well as act at the level of the pancreatic beta cells, where it inhibits different steps of the insulin secretion process. This phenomenon is probably responsible for the passage from an impairment of glucose tolerance to an overt diabetes mellitus in susceptible patients with Cushing’s syndrome.