Cushing's syndrome of nonpituitary causes

Adrenocortical Challenge Response and Genomic Analyses in Scottish Terriers With Increased Alkaline Phosphate Activity

Scottish terriers (ST) frequently have increased serum alkaline phosphatase (ALP) of the steroid isoform. Many of these also have high serum concentrations of adrenal sex steroids. The study's objective was to determine the cause of increased sex steroids in ST with increased ALP. Adrenal gland suppression and stimulation were compared by low dose dexamethasone (LDDS), human chorionic gonadotropin (HCG) and adrenocorticotropic hormone (ACTH) response tests. Resting plasma pituitary hormones were measured. Steroidogenesis-related mRNA expression was evaluated in six ST with increased ALP, eight dogs of other breeds with pituitary-dependent hyperadrenocorticism (HAC), and seven normal dogs. The genome-wide association of single nucleotide polymorphisms (SNP) with ALP activity was evaluated in 168 ST. ALP (reference interval 8–70 U/L) was high in all ST (1,054 U/L) and HAC (985 U/L) dogs. All HAC dogs and 2/8 ST had increased cortisol post-ACTH administration. All ST and 2/7 Normal dogs had increased sex steroids post-ACTH. ST and Normal dogs had similar post-challenge adrenal steroid profiles following LDDS and HCG. Surprisingly, mRNA of hydroxysteroid 17-beta dehydrogenase 2 (HSD17B2) was lower in ST and Normal dogs than HAC. HSD17B2 facilities metabolism of sex steroids. A SNP region was identified on chromosome 5 in proximity to HSD17B2 that correlated with increased serum ALP. ST in this study with increased ALP had a normal pituitary-adrenal axis in relationship to glucocorticoids and luteinizing hormone. We speculate the identified SNP and HSD17B2 gene may have a role in the pathogenesis of elevated sex steroids and ALP in ST.

The risks of overlooking the diagnosis of secreting pituitary adenomas

Secreting pituitary adenomas that cause acromegaly and Cushing’s disease, as well as prolactinomas and thyrotroph adenomas, are uncommon, usually benign, slow-growing tumours. The rarity of these conditions means that their diagnosis is not familiar to most non-specialist physicians. Consequently, pituitary adenomas may be overlooked and remain untreated, and affected individuals may develop serious comorbidities that reduce their quality of life and life expectancy. Because many signs and symptoms of pituitary adenomas overlap with those of other, more common disorders, general practitioners and non-endocrinology specialists need to be aware of the “red flags” suggestive of these conditions. A long duration of active disease in patients with secreting pituitary adenomas is associated with an increased risk of comorbidities and reduced quality of life. Appropriate treatment can lead to disease remission, and, although some symptoms may persist in some patients, treatment usually reduces the incidence and severity of comorbidities and improves quality of life. Therefore, correct, early diagnosis and characterization of a pituitary adenoma is crucial for patients, to trigger timely, appropriate treatment and to optimize outcome. This article provides an overview of the epidemiology of hormonal syndromes associated with pituitary adenomas, discusses the difficulties of and considerations for their diagnosis, and reviews the comorbidities that may develop, but can be prevented, by accurate diagnosis and appropriate treatment. We hope this review will help general practitioners and non-endocrinology specialists to suspect secreting pituitary adenomas and refer patients to an endocrinologist for confirmation of the diagnosis and treatment.

Clinicopathological correlates of adrenal Cushing's syndrome

Endogenous Cushing's syndrome is a rare endocrine disorder that incurs significant cardiovascular morbidity and mortality, due to glucocorticoid excess. It comprises adrenal (20%) and non-adrenal (80%) aetiologies. While the majority of cases are attributed to pituitary or ectopic corticotropin (ACTH) overproduction, primary cortisol-producing adrenal cortical lesions are increasingly recognised in the pathophysiology of Cushing's syndrome. Our understanding of this disease has progressed substantially over the past decade. Recently, important mechanisms underlying the pathogenesis of adrenal hypercortisolism have been elucidated with the discovery of mutations in cyclic AMP signalling (PRKACA, PRKAR1A, GNAS, PDE11A, PDE8B), armadillo repeat containing 5 gene (ARMC5) a putative tumour suppressor gene, aberrant G-protein-coupled receptors, and intra-adrenal secretion of ACTH. Accurate subtyping of Cushing's syndrome is crucial for treatment decision-making and requires a complete integration of clinical, biochemical, imaging and pathology findings. Pathological correlates in the adrenal glands include hyperplasia, adenoma and carcinoma. While the most common presentation is diffuse adrenocortical hyperplasia secondary to excess ACTH production, this entity is usually treated with pituitary or ectopic tumour resection. Therefore, when confronted with adrenalectomy specimens in the setting of Cushing's syndrome, surgical pathologists are most commonly exposed to adrenocortical adenomas, carcinomas and primary macronodular or micronodular hyperplasia. This review provides an update on the rapidly evolving knowledge of adrenal Cushing's syndrome and discusses the clinicopathological correlations of this important disease.

Cushing's syndrome: from physiological principles to diagnosis and clinical care

The physiological control of cortisol synthesis in the adrenal cortex involves stimulation of adrenocorticotrophic hormone (ACTH) by hypothalamic corticotrophin-releasing hormone (CRH) and then stimulation of the adrenal by ACTH. The control loop of the hypothalamic-pituitary-adrenal (HPA) axis is closed by negative feedback of cortisol on the hypothalamus and pituitary. Understanding this system is required to master the diagnosis, differential diagnosis and treatment of endogenous hypercortisolism--Cushing's syndrome. Endogenous Cushing's syndrome is caused either by excess ACTH secretion or by autonomous cortisol release from the adrenal cortex. Diagnosis of cortisol excess exploits three physiological principles: failure to achieve the normal nadir in the cortisol diurnal rhythm, loss of sensitivity of ACTH-secreting tumours to cortisol negative feedback, and increased excretion of free cortisol in the urine. Differentiating a pituitary source of excess ACTH (Cushing's disease) from an ectopic source is accomplished by imaging the pituitary and sampling for ACTH in the venous drainage of the pituitary. With surgical removal of ACTH or cortisol-secreting tumours, secondary adrenal insufficiency ensues because of the prior suppression of the HPA axis by glucocorticoid negative feedback. Medical therapy is targeted to the anatomical location of the dysregulated component of the HPA axis. Future research will focus on new diagnostics and treatments of Cushing's syndrome. These are elegant examples of translational research: understanding basic physiology informs the development of new approaches to diagnosis and treatment. Appreciating pathophysiology generates new areas for inquiry of basic physiological and biochemical mechanisms.

Physiological basis for the etiology, diagnosis, and treatment of adrenal disorders: Cushing's syndrome, adrenal insufficiency, and congenital adrenal hyperplasia

The hypothalamic-pituitary-adrenal (HPA) axis is a classic neuroendocrine system. One of the best ways to understand the HPA axis is to appreciate its dynamics in the variety of diseases and syndromes that affect it. Excess glucocorticoid activity can be due to endogenous cortisol overproduction (spontaneous Cushing's syndrome) or exogenous glucocorticoid therapy (iatrogenic Cushing's syndrome). Endogenous Cushing's syndrome can be subdivided into ACTH-dependent and ACTH-independent, the latter of which is usually due to autonomous adrenal overproduction. The former can be due to a pituitary corticotroph tumor (usually benign) or ectopic ACTH production from tumors outside the pituitary; both of these tumor types overexpress the proopiomelanocortin gene. The converse of Cushing's syndrome is the lack of normal cortisol secretion and is usually due to adrenal destruction (primary adrenal insufficiency) or hypopituitarism (secondary adrenal insufficiency). Secondary adrenal insufficiency can also result from a rapid discontinuation of long-term, pharmacological glucocorticoid therapy because of HPA axis suppression and adrenal atrophy. Finally, mutations in the steroidogenic enzymes of the adrenal cortex can lead to congenital adrenal hyperplasia and an increase in precursor steroids, particularly androgens. When present in utero, this can lead to masculinization of a female fetus. An understanding of the dynamics of the HPA axis is necessary to master the diagnosis and differential diagnosis of pituitary-adrenal diseases. Furthermore, understanding the pathophysiology of the HPA axis gives great insight into its normal control.

Managing Cushing's disease: the state of the art

Cushing's disease is a rare chronic disease caused by a pituitary adenoma, which leads to excess secretion of adrenocorticotropic hormone (ACTH). The over-production of ACTH leads to hyperstimulation of the adrenal glands and a chronic excess of cortisol, resulting in the signs and symptoms of a severe clinical state (Cushing's syndrome) that leads to significant morbidity, negative impacts on the patient's quality of life, and, if untreated, increased mortality. The management of patients with Cushing's disease is complicated by the heterogeneity of the condition, with signs and symptoms that overlap with those of other diseases, and high subclinical incidence rates. Controversies surrounding the tests used for screening and identifying patients with Cushing's disease add to the challenge of patient management. Surgical intervention to remove the adenoma is the first-line treatment for patients with Cushing's disease, but medical therapies are useful in patients who relapse or are unsuitable for surgery. The recent introduction of pasireotide, the first pituitary-directed medical therapy, expands the number of treatment options available for patients with Cushing's disease. This state-of-the-art review aims to provide an overview of the most recent scientific research and clinical information regarding Cushing's disease. Continuing research into improving the diagnosis and treatment of Cushing's disease will help to optimize patient management.

Short-term and long-term orthopaedic issues in patients with fragility fractures

BACKGROUND

Patients with impaired bone quality who suffer a fragility fracture face substantial challenges in both their short- and long-term care. In addition to poor bone quality, many of these patients have multiple medical comorbidities that alter their surgical risk and affect their ultimate functional recovery. Some medical issues can contribute to the altered bone quality and must be addressed to prevent future fractures.

QUESTIONS/PURPOSES

This review summarizes the modifications in perioperative management and fracture fixation in patients with common fragility fractures who have impaired bone quality. It also summarizes the postoperative diagnosis and treatment of secondary causes of impaired bone quality in these patients.

METHODS

We performed a PubMed search, and literature published after 2000 was prioritized, with the exception of benchmark clinical trial studies published before 2000.

RESULTS

Patients with altered bone quality require rapid perioperative management of multiple medical comorbidities. Implant selection in patients with poor quality bone should permit early weightbearing, and constructs should maximize surface area contact with the remaining bone. Long-term diagnosis and treatment of other disease states contributing to poor bone quality (vitamin D deficiency/insufficiency, hypothyroidism, hyperthyroidism, hyperparathyroidism, Cushing's disease, and hypogonadism) must occur to minimize the chances of future fractures.

CONCLUSIONS

Recognition of patients with impaired bone quality and proper treatment of their special needs in both the short and long term are essential for their best opportunity for maximal functional recovery and prevention of future fractures.