The first simultaneous kidney-adrenal gland-pancreas transplantation: outcome at 1 year

Future directions for adrenal insufficiency: cellular transplantation and genetic therapies

Primary adrenal insufficiency occurs in 1 in 5-7000 adults. Leading aetiologies are autoimmune adrenalitis in adults and congenital adrenal hyperplasia (CAH) in children. Oral replacement of cortisol is lifesaving, but poor quality of life, repeated adrenal crises and dosing uncertainty related to lack of a validated biomarker for glucocorticoid sufficiency, persists. Adrenocortical cell therapy and gene therapy may obviate many of the shortcomings of adrenal hormone replacement. Physiological cortisol secretion regulated by pituitary adrenocorticotropin, could be achieved through allogeneic adrenocortical cell transplantation, production of adrenal-like steroidogenic cells from either stem cells or lineage conversion of differentiated cells, or for CAH, gene therapy to replace or repair a defective gene. The adrenal cortex is a high turnover organ and thus failure to incorporate progenitor cells within a transplant will ultimately result in graft exhaustion. Identification of adrenocortical progenitor cells is equally important in gene therapy where new genetic material must be specifically integrated into the genome of progenitors to ensure a durable effect. Delivery of gene editing machinery and a donor template, allowing targeted correction of the 21-hydroxylase gene, has the potential to achieve this. This review describes advances in adrenal cell transplants and gene therapy that may allow physiological cortisol production for children and adults with primary adrenal insufficiency.

Adrenal insufficiency

Adrenal insufficiency (AI), first described by Thomas Addison in 1855, is characterised by inadequate hormonal production by the adrenal gland, which could either be primary, due to destruction of the adrenal cortex, or secondary/tertiary, due to lack of adrenocorticotropic hormone or its stimulation by corticotropin-releasing hormone. This was an invariably fatal condition in Addison's days with most patients dying within a few years of diagnosis. However, discovery of cortisone in the 1940s not only improved the life expectancy of these patients but also had a dramatic effect on their overall quality of life. The diagnosis, easily confirmed by demonstrating inappropriately low cortisol secretion, is often delayed by months, and many patients present with acute adrenal crisis. Sudden withdrawal from chronic glucocorticoid therapy is the most common cause of AI. Currently, there remains a wide variation in the management of this condition across Europe. As primary AI is a relatively rare condition, most medical specialists will only manage a handful of these patients in their career. Despite many advances in recent years, there is currently no curative option, and modern cortisol replacement regimens fail to adequately mimic physiological cortisol rhythm. A number of new approaches including allograft of adrenocortical tissue and stem cell therapy are being tried but remain largely experimental.

Glucocorticoid replacement therapies: past, present and future

Since the original description of adrenal insufficiency by Thomas Addison in 1855, there has been an exponential growth in the understanding of adrenal gland biology and its role in the hypothalamic-pituitary-adrenal axis. Despite this, the mainstay of therapeutic glucocorticoid replacement for most clinicians has remained unchanged for nearly 50 years. More recently, there has been better recognition of the morbidity and mortality associated with current approaches and the challenges to tackle in reducing this and improving clinical outcomes. In this review, we have summarised the history of glucocorticoid replacement therapy from its nascence in the 1930s, through common practice and culminating in more recent glucocorticoid replacement strategies plus the potential of stem cell therapy in the future.

Adrenal crises in older patients

Adrenal crises are severe manifestations of adrenal insufficiency that result in hospital admission and incur a risk of cardiovascular events, acute renal injury, and death. Evidence from population-based studies indicate that adults older than 60 years have the highest adrenal insufficiency incidence, contribute to the highest number of adrenal crises, and have the highest age-specific incidence of adrenal crisis, which doubles between the age groups of 60-69 years and 80 years or older. Older patients might be more susceptible to adrenal crises because of a higher prevalence of comorbidities and a consequently higher risk of acute illness. This susceptibility might be compounded by shortfalls in the implementation of prevention strategies for adrenal crisis, because of individual and social factors that increase with age. Although little research has focused on adrenal crisis prevention in older patients, it seems logical that a timely diagnosis of adrenal insufficiency and the use of consensus driven adrenal crisis prevention and attenuation strategies might reduce adrenal crises in patients older than 60 years old.

New directions for the treatment of adrenal insufficiency

Adrenal disease, whether primary, caused by defects in the hypothalamic-pituitary-adrenal (HPA) axis, or secondary, caused by defects outside the HPA axis, usually results in adrenal insufficiency, which requires lifelong daily replacement of corticosteroids. However, this kind of therapy is far from ideal as physiological demand for steroids varies considerably throughout the day and increases during periods of stress. The development of alternative curative strategies is therefore needed. In this review, we describe the latest technologies aimed at either isolating or generating de novo cells that could be used for novel, regenerative medicine application in the adrenocortical field.

Diagnosis and management of adrenal insufficiency

Adrenal insufficiency continues to be a challenge for patients, their physicians, and researchers. During the past decade, long-term studies have shown increased mortality and morbidity and impaired quality of life in patients with adrenal insufficiency. These findings might, at least partially, be due to the failure of glucocorticoid replacement therapy to closely resemble physiological diurnal secretion of cortisol. The potential effect of newly developed glucocorticoid drugs is a focus of research, as are the mechanisms potentially underlying increased morbidity and mortality. Adrenal crisis remains a threat to lives, and awareness and preventative measures now receive increasing attention. Awareness should be raised in medical teams and patients about adrenal insufficiency and management of adrenal crisis to improve clinical outcome.