Cushing's syndrome

Cushing's syndrome remains one of the most challenging problems in clinical endocrinology. Cushing's disease is caused in the majority of cases by basophil pituitary microadenomas which may be successfully treated by trans-sphenoidal hypophysectomy. Treatment with metyrapone or o,p'-DDD can always induce a clinical remission but not a cure, and neurotransmitter therapy may be effective in a minority of cases. Pituitary irradiation cures about half of cases in the long-term and may be used for surgical failures. Tumours producing ectopic ACTH are frequently benign, small and occult and may produce a syndrome clinically indistinguishable from Cushing's disease. Biochemical investigations cannot absolutely distinguish pituitary from ectopic sources of ACTH and therefore body CT scanning and percatheter venous sampling are essential diagnostic investigations. Tumour localization may result in resection and complete cure, although even small tumours may have a malignant potential. Adrenal tumours are readily diagnosed by plasma ACTH measurement and adrenal CT scanning. Adrenal adenomas are cured by adrenalectomy. Carcinomas may be treated by a combination of adrenalectomy, radiotherapy and o,p'-DDD, but long-term prognosis is poor.     

Cushing's syndrome

The clinical characteristics and current concepts of pathophysiology of Cushing's syndrome have been reviewed. The specific type of pituitary or ectopic ACTH-dependent and ACTH-independent Cushing's syndrome and the underlying pathology can be determined biochemically and with the aid of anatomic localization procedures. Several approaches are available for treating pituitary ACTH-dependent Cushing's syndrome, but transsphenoidal pituitary microsurgery is the ideal type, with remission of the disease being observed in 80 to 90% of cases. When successful, pituitary microsurgery is followed by preservation of normal pituitary function and restoration of normal hypothalamic-pituitary-adrenal function within 6 to 12 months postoperatively. Medical therapy of Cushing's disease includes drugs that inhibit CRH-ACTH secretion, such as cyproheptadine and bromocriptine, and agents that inhibit cortisol synthesis, such as aminoglutethimide, metyrapone, ketoconazole, and mitotane, or that block the action of cortisol at the glucocorticoid receptor level, such as RU-485. With the exception of mitotane, which has adrenalytic effects, the action of the other pharmacologic agents is promptly reversed when treatment is discontinued. Thus, drug therapy is effective only as temporary treatment for Cushing's syndrome when surgical approaches are contraindicated or when attempts are made to improve the patient's clinical and metabolic status in preparation for surgery. Mitotane is effective in extending survival of patients with adrenal carcinoma, particularly when it is administered early as adjuvant therapy or when it is combined with repeated debulking resection of recurrent tumor. The toxicity associated with mitotane administration limits the use of larger and probably more effective doses in these patients. The synthesis of more specific cytochrome P-450 enzyme inhibitors and of mitotane analogues with more limited toxicity may ultimately provide more effective tools in the pharmacologic management of Cushing's syndrome.     

Cushing's syndrome

Cushing's syndrome results from lengthy and inappropriate exposure to excessive glucocorticoids. Untreated, it has significant morbidity and mortality. The syndrome remains a challenge to diagnose and manage. Here, we review the current understanding of pathogenesis, clinical features, diagnostic, and differential diagnostic approaches. We provide diagnostic algorithms and recommendations for management.     

Cushing's syndrome

During the past 30 years, there have been advances in understanding of the pathogenesis of Cushing's syndrome and in differential diagnosis of its various forms. Improved diagnostic tests and procedures have increased the ability to recognise even mild hypercortisolism and have provided the means to obtain an accurate diagnosis. Despite these advances, the occurrence of unusual clinical presentations and laboratory shortcomings may produce diagnostic problems and challenge clinical intuition. This article reviews recent pathogenic views, new tests, and new diagnostic problems in the evaluation of Cushing's syndrome. Atypical clinical presentations of hypercortisolism and some laboratory shortcomings that may confuse the diagnosis of Cushing's syndrome are also reported.     

Megestrol-induced Cushing's syndrome

This case describes the first report of a patient developing Cushing's syndrome whilst being treated with the synthetic progestogen, megestrol acetate (Megace). Drugs are the commonest cause of Cushing's syndrome. Some synthetic progestogens are known to have glucocorticoid activity at high doses. On structural grounds neither megestrol nor its major metaboiltes would be expected to interact with the glucocorticoid receptor, though the manufacturers report that it may have ‘weak glucocorticoid activity'.     

Subclinical Cushing's syndrome

Subclinical Cushing's syndrome (CS) is attracting increasing interest since the serendipitous discovery of an adrenal mass has become a rather frequent event owing to the routine use of sophisticated radiologic techniques. Cortical adenoma is the most frequent type of adrenal incidentaloma accounting for approximately 50% of cases in surgical series and even greater shares in medical series. Incidentally discovered adrenal adenomas may secrete cortisol in an autonomous manner that is not fully restrained by pituitary feedback, in 5 to 20% of cases depending on study protocols and diagnostic criteria. The criteria for qualifying subclinical cortisol excess are controversial and presently there is no consensus on a gold standard for the diagnosis of this condition. An increased frequency of hypertension, central obesity, impaired glucose tolerance, diabetes and hyperlipemia has been described in patients with subclinical CS; however, there is still no clear demonstration of the long-term complications of this condition whose management remains largely empirical. Either adrenalectomy or careful observation associated with treatment of the metabolic syndrome have been suggested as treatment options.     

Cyclic Cushing's syndrome

Because glucocorticoids are necessary to sustain life and maintain homeostasis, adrenal disorders, if not detected in a timely fashion, can have serious consequences. Cyclic Cushing's syndrome is a disease characterized by rhythmic fluctuations in glucocorticoid production. In patients with this disorder, both clinical and biochemical spontaneous remissions may occur and therefore the activity of the hypothalamic-pituitary-adrenal axis between the cycles may be undisturbed. The clinical manifestation of cyclic Cushing's syndrome may be complex and varied, differing not only between patients but also in the same patient on a daily to monthly basis. The presence of cyclic Cushing's syndrome should always be considered in patients with a clinical presentation of hypercortisolism coexisting with normal glucocorticoid plasma levels and a paradoxical response to the dexamethasone test. We here present a detailed case report on a patient diagnosed with cyclic Cushing's syndrome. We report diagnostic and treatment strategies used in our patient and their impact on the course and outcome of the disease.     

Familial Cushing's syndrome

Cushing's syndrome has been demonstrated in four of seven siblings with clinical manifestations appearing around puberty in three of the four siblings. The only other associated findings in these cases were short stature and disturbed carbohydrate metabolism. Adenomatous hyperplasia of the adrenal glands was demonstrated in 3 of the patients, and a virilizing adrenal carcinoma in the fourth sibling. The pathogenesis of the adrenocortical disorders in these siblings is discussed.     

Factitious Cushing's syndrome

In this report we describe a patient who produced the clinical and laboratory features of Cushing's syndrome by injecting himself for many months with hydrocortisone. Factitious Cushing's syndrome is a variant of the Münchausen syndrome and should be considered if tests used to establish the diagnosis of Cushing's syndrome appear incongruous particularly in subjects with access to medical intelligence and drugs.     

Factitious Cushing's syndrome

A woman with pituitary-dependent Cushing's disease remained hypercortisolemic after bilateral adrenalectomy. A search for an adrenal remnant by venous catheterization study suggested persistent cortisol-secreting tissue in the left adrenal bed. During ACTH stimulation, plasma corticosterone concentrations remained low and cortisol remained high, suggesting the cortisol was of exogenous origin. Cushingoid features resolved after confronting the patient with this evidence. Plasma corticosterone concentrations played a novel role in the diagnosis of factitiously induced Cushing's syndrome in this patient.     

Asthma and Cushing's syndrome

A female patient was treated with high-dose inhaled fluticasone propionate for her asthma. Over 2 years, she developed features of Cushing's syndrome with proximal myopathy, osteopenia, hypertension, depressive psychosis, and cushingoid appearance. She had biochemical evidence of marked adrenal suppression with a 9:00 AM serum cortisol of 20 nmol/L that returned to normal (315 mol/L) after her therapy was changed to budenoside, 0.8 mg/d. Her appearance, mental state, and myopathy also improved with no loss of asthma control. This case illustrates the potential for developing clinically relevant adverse effects of inhaled corticosteroids when given at licensed doses.     

Cushing's syndrome during pregnancy

Two cases of Cushing's syndrome during pregnancy are reported, both due to an adrenal adenoma. The association of pregnancy and Cushing's syndrome has up to now been described in 48 patients (including our two cases); Cushing's syndrome was ACTH-independent in 59%, ACTH-dependent in 33%, and of unknown cause in 8%. The obvious preponderance of ACTH-independent Cushing's syndrome in pregnancy--in contrast to the higher prevalence of ACTH-dependent Cushing's syndrome in the nonpregnant state--is unexplained, but might be related to less severe hypercortisolism in patients with adrenal adenoma. Active treatment of Cushing's syndrome in pregnancy is associated with a slightly but not significantly better outcome of pregnancy.     

Hypertension in Cushing's syndrome

Cushing's syndrome can be exogenous, resulting from the administration of glucocorticoids or adrenocorticotrophic hormone (ACTH), or endogenous, secondary to increased secretion of cortisol or ACTH. Hypertension is one of the most distinguishing features of endogenous Cushing's syndrome, as it is present in about 80% of adult patients and in almost half of children and adolescents patients. Hypertension results from the interplay of several pathophysiological mechanisms regulating plasma volume, peripheral vascular resistance and cardiac output, all of which may be increased. The therapeutic goal is to find and remove the cause of excess glucocorticoids, which, in most cases of endogenous Cushing's syndrome, is achieved surgically. Treatment of Cushing's syndrome usually results in resolution or amelioration of hypertension. However, some patients may not achieve normotension or may require a prolonged period of time for the correction of hypercortisolism. Therefore, therapeutic strategies for Cushing's-specific hypertension (to normalise blood pressure and decrease the duration of hypertension) are necessary to decrease the morbidity and mortality associated with this disorder. The various pathogenetic mechanisms that have been proposed for the development of glucocorticoid-induced hypertension in Cushing's syndrome and its management are discussed.     

Subclinical Cushing's syndrome.

Classic Cushing's syndrome is a rare disease with an estimated incidence of 1 case per 100,000 persons. With routine use of imaging techniques such as ultrasound and CT, adrenal masses are being detected with increased frequency. A substantial percentage of these incidentalomas are hormonally active, with 5% to 20% of the tumors producing glucocorticoids. Autonomous glucocorticoid production without specific signs and symptoms of Cushing's syndrome is termed subclinical Cushing's syndrome. With an estimated prevalence of 79 cases per 100,000 persons, subclinical Cushing's syndrome is much more common than classic Cushing's syndrome. Depending on the amounts of glucocorticoids secreted by the tumor, the clinical spectrum ranges from slightly attenuated diurnal cortisol rhythm to complete atrophy of the contralateral adrenal gland with lasting adrenal insufficiency after unilateral adrenalectomy. Patients with subclinical Cushing's syndrome lack the classical stigmata of hypercortisolism but have a high prevalence of obesity, hypertension, and type 2 diabetes. All patients with incidentally detected adrenal masses scheduled for surgery must undergo testing for subclinical Cushing's syndrome to avoid postoperative adrenal crisis. The best screening test to uncover autonomous cortisol secretion is the short dexamethasone suppression test. Because the adrenal origin of a pathologic cortisol secretion is anticipated, the author prefers a higher dexamethasone dose (3 mg instead of 1 mg) to reduce false-positive results. A suppressed serum cortisol level of less than 3 micrograms/dL (80 nmol/L) after dexamethasone excludes significant cortisol secretion by the tumor. A serum cortisol level greater than 3 micrograms/dL requires further investigation, including confirmation by high-dose dexamethasone (8 mg) suppression testing, a CRH test, and analysis of diurnal rhythm. Determination of urinary free cortisol is less useful because increased values are a late finding usually associated with emerging clinical signs of Cushing's syndrome. Patients with suppressed plasma ACTH in response to CRH generally have adrenal insufficiency after surgery and require adequate perioperative and postoperative substitution therapy. Whether patients with subclinical Cushing's syndrome should undergo adrenalectomy is a matter of debate. The author performs surgery in young patients (< 50 years), in patients with suppressed plasma ACTH, and in patients with a recent history of weight gain, substantial obesity, arterial hypertension, diabetes mellitus, and osteopenia. In completely asymptomatic patients with normal plasma ACTH concentrations and in patients older than 75 years, the author recommends a nonsurgical approach. A large prospective randomized study is necessary to evaluate the benefits of surgery versus conservative treatment in patients with subclinical Cushing's syndrome.