James W. Findling

Liddle's syndrome: Heritable human hypertension caused by mutations in the β subunit of the epithelial sodium channel

Liddles syndrome (pseudoaldosteronism) is an autosomal dominant form of human hypertension characterized by a constellation of findings suggesting constitutive activation of the amiloride-sensitive distal renal epithelial sodium channel. We demonstrate complete linkage of the gene encoding the beta subunit of the epithelial sodium channel to Liddles syndrome in Liddles original kindred. Analysis of this gene reveals a premature stop codon that truncates the cytoplasmic carboxyl terminus of the encoded protein in affected subjects. Analysis of subjects with Liddles syndrome from four additional kindreds demonstrates either premature termination or frameshift mutations in this same carboxy-terminal domain in all four. These findings demonstrate that Liddles syndrome is caused by mutations in the beta subunit of the epithelial sodium channel and have implications for the regulation of this epithelial ion channel as well as blood pressure homeostasis.

The Diagnosis of Cushing's Syndrome: An Endocrine Society Clinical Practice Guideline

OBJECTIVE The objective of the study was to develop clinical practice guidelines for the diagnosis of Cushings syndrome. PARTICIPANTS The Task Force included a chair, selected by the Clinical Guidelines Subcommittee (CGS) of The Endocrine Society, five additional experts, a methodologist, and a medical writer. The Task Force received no corporate funding or remuneration. CONSENSUS PROCESS Consensus was guided by systematic reviews of evidence and discussions. The guidelines were reviewed and approved sequentially by The Endocrine Societys CGS and Clinical Affairs Core Committee, members responding to a web posting, and The Endocrine Society Council. At each stage the Task Force incorporated needed changes in response to written comments. CONCLUSIONS After excluding exogenous glucocorticoid use, we recommend testing for Cushings syndrome in patients with multiple and progressive features compatible with the syndrome, particularly those with a high discriminatory value, and patients with adrenal incidentaloma. We recommend initial use of one test with high diagnostic accuracy (urine cortisol, late night salivary cortisol, 1 mg overnight or 2 mg 48-h dexamethasone suppression test). We recommend that patients with an abnormal result see an endocrinologist and undergo a second test, either one of the above or, in some cases, a serum midnight cortisol or dexamethasone-CRH test. Patients with concordant abnormal results should undergo testing for the cause of Cushings syndrome. Patients with concordant normal results should not undergo further evaluation. We recommend additional testing in patients with discordant results, normal responses suspected of cyclic hypercortisolism, or initially normal responses who accumulate additional features over time.

A 12-Month Phase 3 Study of Pasireotide in Cushing's Disease

BACKGROUND Cushings disease is associated with high morbidity and mortality. Pasireotide, a potential therapy, has a unique, broad somatostatin-receptor-binding profile, with high binding affinity for somatostatin-receptor subtype 5. METHODS In this double-blind, phase 3 study, we randomly assigned 162 adults with Cushings disease and a urinary free cortisol level of at least 1.5 times the upper limit of the normal range to receive subcutaneous pasireotide at a dose of 600 μg (82 patients) or 900 μg (80 patients) twice daily. Patients with urinary free cortisol not exceeding 2 times the upper limit of the normal range and not exceeding the baseline level at month 3 continued to receive their randomly assigned dose; all others received an additional 300 μg twice daily. The primary end point was a urinary free cortisol level at or below the upper limit of the normal range at month 6 without an increased dose. Open-label treatment continued through month 12. RESULTS Twelve of the 82 patients in the 600-μg group and 21 of the 80 patients in the 900-μg group met the primary end point. The median urinary free cortisol level decreased by approximately 50% by month 2 and remained stable in both groups. A normal urinary free cortisol level was achieved more frequently in patients with baseline levels not exceeding 5 times the upper limit of the normal range than in patients with higher baseline levels. Serum and salivary cortisol and plasma corticotropin levels decreased, and clinical signs and symptoms of Cushings disease diminished. Pasireotide was associated with hyperglycemia-related adverse events in 118 of 162 patients; other adverse events were similar to those associated with other somatostatin analogues. Despite declines in cortisol levels, blood glucose and glycated hemoglobin levels increased soon after treatment initiation and then stabilized; treatment with a glucose-lowering medication was initiated in 74 of 162 patients. CONCLUSIONS The significant decrease in cortisol levels in patients with Cushings disease who received pasireotide supports its potential use as a targeted treatment for corticotropin-secreting pituitary adenomas. (Funded by Novartis Pharma; ClinicalTrials.gov number, NCT00434148.).

Treatment of Pituitary-Dependent Cushing’s Disease with the Multireceptor Ligand Somatostatin Analog Pasireotide (SOM230): A Multicenter, Phase II Trial

CONTEXT There is currently no medical therapy for Cushings disease that targets the pituitary adenoma. Availability of such a medical therapy would be a valuable therapeutic option for the management of this disorder. OBJECTIVE Our objective was to evaluate the short-term efficacy of the novel multireceptor ligand somatostatin analog pasireotide in patients with de novo, persistent, or recurrent Cushings disease. DESIGN We conducted a phase II, proof-of-concept, open-label, single-arm, 15-d multicenter study. PATIENTS Thirty-nine patients with either de novo Cushings disease who were candidates for pituitary surgery or with persistent or recurrent Cushings disease after surgery without having received prior pituitary irradiation. INTERVENTION Patients self-administered sc pasireotide 600 microg twice daily for 15 d. MAIN OUTCOME MEASURE Normalization of urinary free cortisol (UFC) levels after 15 d treatment was the main outcome measure. RESULTS Of the 29 patients in the primary efficacy analysis, 22 (76%) showed a reduction in UFC levels, of whom five (17%) had normal UFC levels (responders), after 15 d of treatment with pasireotide. Serum cortisol levels and plasma ACTH levels were also reduced. Steady-state plasma concentrations of pasireotide were achieved within 5 d of treatment. Responders appeared to have higher pasireotide exposure than nonresponders. CONCLUSIONS Pasireotide produced a decrease in UFC levels in 76% of patients with Cushings disease during the treatment period of 15 d, with direct effects on ACTH release. These results suggest that pasireotide holds promise as an effective medical treatment for this disorder.

Mifepristone, a glucocorticoid receptor antagonist, produces clinical and metabolic benefits in patients with Cushing's syndrome.

CONTEXT Cushings syndrome (CS) is a disorder associated with significant morbidity and mortality due to prolonged exposure to high cortisol concentrations. OBJECTIVE Our objective was to evaluate the safety and efficacy of mifepristone, a glucocorticoid receptor antagonist, in endogenous CS. DESIGN AND SETTING We conducted a 24-wk multicenter, open-label trial after failed multimodality therapy at 14 U.S. academic medical centers and three private research centers. PARTICIPANTS Participants included 50 adults with endogenous CS associated with type 2 diabetes mellitus/impaired glucose tolerance (C-DM) or a diagnosis of hypertension alone (C-HT). INTERVENTION Mifepristone was administered at doses of 300-1200 mg daily. MAIN OUTCOME MEASURES We evaluated change in area under the curve for glucose on 2-h oral glucose test for C-DM and change in diastolic blood pressure from baseline to wk 24 for C-HT. RESULTS In the C-DM cohort, an area under the curve for glucose (AUC(glucose)) response was seen in 60% of patients (P < 0.0001). Mean ± sd glycated hemoglobin (HbA1c) decreased from 7.43 ± 1.52% to 6.29 ± 0.99% (P < 0.001); fasting plasma glucose decreased from 149.0 ± 75.7 mg/dl (8.3 ± 4.1 mmol/liter) to 104.7 ± 37.5 mg/dl (5.8 ± 2.1 mmol/liter, P < 0.03). In C-HT cohort, a diastolic blood pressure response was seen in 38% of patients (P < 0.05). Mean weight change was -5.7 ± 7.4% (P < 0.001) with waist circumference decrease of -6.78 ± 5.8 cm (P < 0.001) in women and -8.44 ± 5.9 cm (P < 0.001) in men. Overall, 87% (P < 0.0001) had significant improvement in clinical status. Insulin resistance, depression, cognition, and quality of life also improved. Common adverse events were fatigue, nausea, headache, low potassium, arthralgia, vomiting, edema, and endometrial thickening in women. CONCLUSIONS Mifepristone produced significant clinical and metabolic improvement in patients with CS with an acceptable risk-benefit profile during 6 months of treatment.

Treatment of Cushing's Syndrome: An Endocrine Society Clinical Practice Guideline.

OBJECTIVE The objective is to formulate clinical practice guidelines for treating Cushings syndrome. PARTICIPANTS Participants include an Endocrine Society-appointed Task Force of experts, a methodologist, and a medical writer. The European Society for Endocrinology co-sponsored the guideline. EVIDENCE The Task Force used the Grading of Recommendations, Assessment, Development, and Evaluation system to describe the strength of recommendations and the quality of evidence. The Task Force commissioned three systematic reviews and used the best available evidence from other published systematic reviews and individual studies. CONSENSUS PROCESS The Task Force achieved consensus through one group meeting, several conference calls, and numerous e-mail communications. Committees and members of The Endocrine Society and the European Society of Endocrinology reviewed and commented on preliminary drafts of these guidelines. CONCLUSIONS Treatment of Cushings syndrome is essential to reduce mortality and associated comorbidities. Effective treatment includes the normalization of cortisol levels or action. It also includes the normalization of comorbidities via directly treating the cause of Cushings syndrome and by adjunctive treatments (eg, antihypertensives). Surgical resection of the causal lesion(s) is generally the first-line approach. The choice of second-line treatments, including medication, bilateral adrenalectomy, and radiation therapy (for corticotrope tumors), must be individualized to each patient.

A Physiologic Approach to Diagnosis of the Cushing Syndrome

Clinical Principles* General Obesity Hypertension Metabolic Diabetes mellitus or impaired glucose tolerance Hyperlipidemia Nephrolithiasis Polyuria Skin Plethora Hirsutism Striae Acne Bruising Musculoskeletal Osteopenia or osteoporosis Proximal myopathy Neuropsychiatric Depression Cognitive impairment Emotional lability Euphoria Psychosis Gonadal dysfunction Oligomenorrhea or amenorrhea Impotence, decreased libido Immune suppression (susceptible to opportunistic infection) *Notice that many of the features of the Cushing syndrome resemble those of the metabolic syndrome (e.g., obesity, hypertension, impaired glucose tolerance, hyperlipidemia, hirsutism, acne, and gonadal dysfunction). Pathophysiologic Principles The hypothalamicpituitaryadrenal axis Control of adrenal function and growth Hypothalamic control of pituitary function Glucocortcoid-negative feedback Circadian rhythm The stress response Posttranslational processing of proopiomelanocortin to adrenocorticotropic hormone Cortisol plasma binding, metabolism, and excretion Glucocorticoid action 11-hydroxysteroid dehydrogenase type 1 and 11-hydroxysteroid dehydrogenase type 2 The relationship among obesity, impaired glucose tolerance or diabetes, hypertension, and gonadal dysfunction was initially recognized in two clinical syndromes described early in the 20th century. In 1932, Harvey Cushing reported these findings as well as other features of endogenous hypercortisolism in patients with small basophilic pituitary adenomas (1). A decade earlier, two French physicians, Drs. Archard and Thiers, described a similar phenotype in the syndrome that is now recognized as the syndrome of insulin resistance (the metabolic syndrome) and the polycystic ovary syndrome (2). Recently, increasing evidence has shown that the Cushing syndrome is a reversible cause of the metabolic syndrome (3) and that it may be more common than previously thought. Some patients with incidentally discovered adrenocortical tumors have subclinical hypercortisolism and experience clinical improvement in diabetes, hypertension, and obesity after adrenalectomy; this illustrates the importance of discovering even mild cases of the Cushing syndrome (4). In addition, two recent studies found that 2% to 3% of patients with poorly controlled type 2 diabetes mellitus may have unrecognized Cushing syndrome (5, 6). The clinical and biochemical discrimination of true Cushing syndrome from the Cushing phenotype and the metabolic syndrome may be very difficult, particularly when hypercortisolism is mild. Since obesity, hypertension, diabetes, and lipid disorders are common in the general population, it is important for internists and other primary care physicians to be able to identify patients with the Cushing syndrome. This review demonstrates that an understanding of the physiologic characteristics of the hypothalamicpituitaryadrenal axis is essential in formulating strategies to confirm the diagnosis of the Cushing syndrome as well as establish its cause. The Basic Organization of the HypothalamicPituitaryAdrenal Axis The general organization of the hypothalamicpituitaryadrenal axis (Figure 1) has been appreciated for almost half a century. However, many recently described new concepts have significant implications for the understanding of the pathophysiologic characteristics, diagnosis, and treatment of the Cushing syndrome. Figure 1. The hypothalamicpituitaryadrenal control system. CRH AVP ACTH Control of Adrenal Function The primary controller of the synthesis and release of cortisol from the adrenal zona fasciculata is adrenocorticotropic hormone (ACTH) (7). This hormone exerts acute control, causing the plasma cortisol level to increase within minutes of an elevation in ACTH level. The main mechanism of action of ACTH is to activate adenylate cyclase activity, increase cytosolic cyclic adenosine 3,5-monophosphate (cAMP), and activate protein kinase A. This leads to an increase in the rate-limiting step: cholesterol transport from the cytosol across the mitochondrial membrane to provide substrate for the first enzyme in the steroidogenic pathway (P450 side-chain cleavage). At least two proteins expressed within the steroidogenic cellsteroidogenic acute regulatory protein and the peripheral-type benzodiazepine receptormediate this mitochondrial transport step. The mechanisms of action and control of expression of these two proteins are currently an area of intense investigation that has implications for a variety of adrenocortical disorders. Adrenocorticotropic hormone also exerts long-term trophic effects on the adrenal cortex. Prolonged stimulation leads to adrenal hypertrophy (as in bilateral adrenal hyperplasia), and prolonged decreases in ACTH level lead to adrenal atrophy (as in so-called secondary adrenal insufficiency and as observed with long-term glucocorticoid therapy). It is also possible that the steroidogenic acute regulatory protein, the peripheral-type benzodiazepine receptor, or both are involved in the control of adrenocortical growth and atrophy. Synthesis of ACTH Adrenocorticotropic hormone is synthesized as part of a large precursor molecule called proopiomelanocortin (8). Along with other peptides such as lipotropin, ACTH is released from proopiomelanocortin by posttranslational processing within the pituitary corticotroph cells (Figure 2). Furthermore, nonpituitary tumors, which have undergone abnormal differentiation, can synthesize proopiomelanocortin and some or all of its posttranslational products; this explains the ectopic ACTH syndrome. Figure 2. Production of adrenocorticotropic hormone ( ACTH ) in the anterior pituitary corticotroph cell. LPH N N-POC M HypothalamicPituitary Function The release of ACTH from the normal anterior pituitary is controlled by stimulatory and inhibitory inputs (9-11). Most of our knowledge about this system comes from experimental studies in animals. The primary stimulatory input is corticotropin-releasing hormone (CRH), which is synthesized in the parvocellular nerves of the paraventricular nucleus of the hypothalamus and released from their nerve terminals into capillaries in the median eminence. Arginine vasopressin (AVP) synthesized in parvocellular nerves of the paraventricular nucleus is also involved in the control of ACTH (12). This is distinct from AVP released from magnocellular nerve terminals in the posterior pituitary, which controls free water clearance in the kidney (13). Corticotropin-releasing hormone and AVP, once released into capillaries in the median eminence, drain into the anterior pituitary through the long portal veins and increase ACTH release. The other main controller of ACTH release is inhibition through glucocorticoid-negative feedback, which causes cortisol released from the adrenal to ultimately restrain its own release (10, 11). Glucocorticoid-negative feedback is the physiologic basis of the dexamethasone suppression test described later in this review. The release of CRH (and AVP) from parvocellular neurons of the paraventricular nucleus of the hypothalamus into the portal veins is controlled by a variety of neural and hormonal inputs. The response to stress is mediated by neural inputs from several areas within the brain (9-11). For example, hypoglycemia is sensed by the hypothalamic glucose sensors, which have input into the paraventricular nucleus. In addition, the circadian rhythm of cortisol described later in this review is mediated by neural input from the suprachiasmatic nuclei of the hypothalamus. Glucocorticoid-negative feedback also suppresses CRH and AVP by direct action on parvocellular neurons. A newly appreciated mechanism of negative feedback is that glucocorticoids inhibit CRH release from the hypothalamus through input from the hippocampus, which expresses high levels of glucocorticoid receptor (10). In fact, many areas of the central nervous system with input into the hypothalamus can express high levels of the glucocorticoid receptor (14). Circadian Rhythm Cortisol is released episodically. The main rhythm is circadian, in which cortisol level is at its peak around the time of awakening (approximately 7:00 or 8:00 a.m.) and at its nadir at or soon after midnight (14, 15). Changes in this circadian rhythm, ranging from subtle alterations to complete disruption, are common in patients with the Cushing syndrome (15). Detection of these changes can be exploited as a diagnostic tool. Cortisol Metabolism and Mechanisms of Action Metabolism Cortisol circulates in the plasma both in the free (biologically active) form (approximately 5%) and while bound to corticosteroid-binding globulin and albumin (approximately 95%) (16). Cortisol is cleared from the circulation primarily after conjugation to glucuronide in the liver and excretion in the urine. In addition, plasma free cortisol is filtered in the renal glomerulus and appears in the urine as free cortisol. This is the basis for using urine free cortisol level to diagnose hypercortisolism. Mechanisms of Action Appreciation of the distribution of the glucocorticoid receptor and its mechanism of action helps to explain the very wide range of symptoms found in patients with the Cushing syndrome. Glucocorticoid receptors are located within the cell, primarily in the cytoplasm. Binding of cortisol to the glucocorticoid receptor ultimately increases the expression of specific genes (transcription) and synthesis of new proteins (translation). A current area of investigation is the nongenomic actions of cortisol, which may be transduced through the cell membrane. The notion that steroids can activate cellular phenomena through transduction at the cell membrane is a new and exciting area, but its clinical significance is not yet clear (17). Glucocorticoid receptors in the anterior pituitary, hypothalamus, and hippocampus account for glucocorticoid-negative feedback (10, 14, 18). Glucocorticoid receptor expression throughout the brain accounts for man

An Overnight High-Dose Dexamethasone Suppression Test for Rapid Differential Diagnosis of Cushing's Syndrome

We have developed a high-dose dexamethasone suppression test that can be administered overnight with a single 8-mg dose and used the new procedure in the differential diagnosis of 83 patients with Cushings syndrome. In 76 patients with surgically or pathologically proven cause--60 with Cushings disease, 7 with the ectopic adrenocorticotrophic hormone syndrome, and 9 with adrenal tumors--suppression of plasma cortisol levels to less than 50% of baseline indicated a diagnosis of Cushings disease. The test had a sensitivity of 92%, a specificity of 100%, and a diagnostic accuracy of 93%. These values equal or exceed those of the standard 2-day test whether based on suppression of urinary 17-hydroxycorticosteroids or plasma cortisol. We conclude that this overnight, high-dose dexamethasone suppression test is practical and reliable in the differential diagnosis of Cushings syndrome.

DIAGNOSIS AND DIFFERENTIAL DIAGNOSIS OF CUSHING'S SYNDROME

The clinical recognition of Cushings syndrome and its biochemical confirmation is a challenging problem. The best diagnostic approach to patients with suspected Cushings syndrome is still evolving. The traditional diagnostic approach of urine free cortisol and low-dose dexamethasone suppression testing may be inadequate when the degree of hypercortisolism is mild. Late-night salivary cortisol determinations may evolve as the simplest means of screening patients for suspected hypercortisolism. Repeated measurements of cortisol secretion (urine free cortisol or late-night salivary cortisol) over an extended period of time may be necessary to provide diagnostic certainty. The dexamethasone-CRH test is a reasonable approach in patients with equivocal data. The introduction of reliable, sensitive, and specific plasma ACTH measurements, the use of IPSS for ACTH with CRH stimulation, and the improved techniques of pituitary and adrenal imaging have made the differential diagnosis of Cushings syndrome relatively straightforward (see Fig. 2). Clinicians who have never missed the diagnosis of Cushings syndrome or have never been fooled by attempting to establish its cause should refer their patients with suspected hypercortisolism to someone who has.

Selective Venous Sampling for ACTH in Cushing's Syndrome: Differentiation Between Cushing's Disease and the Ectopic ACTH Syndrome

We performed selective venous catheterization and sampling for ACTH in six patients with ACTH-secreting pituitary adenomas (Cushings disease) and four patients with occult ectopic ACTH-secreting neoplasms. In five patients with Cushings disease in whom the inferior petrosal sinus could be catheterized, ACTH levels were unequivocally higher than simultaneous peripheral values: The ratio was greater than 2.0, with a range of 2.2 to 16.7. In contrast, the inferior petrosal sinus-to-peripheral ACTH ratio in three patients with ectopic ACTH secretion was less than 1.5. In the fourth patient, an arteriovenous gradient of 6.8 was shown 2 years before a bronchial carcinoid tumor was clinically apparent. Central-to-peripheral ACTH ratios at the level of the jugular bulb and jugular vein were not diagnostic. We conclude that selective venous ACTH sampling from the inferior petrosal sinus is a reliable and useful aid in the differential diagnosis of Cushings syndrome when standard clinical and biochemical studies are inconclusive.