Familial glucocorticoid deficiency: New genes and mechanisms

Establishment of human induced pluripotent stem cell line SDQLCHi029-A from one Type 1 familial glucocorticoid deficiency patient carrying compound heterozygote mutations in MC2R gene

Type 1 familial glucocorticoid deficiency (FGD) is a rare autosomal recessive disorder due to variation of the melanocortin-2-receptor (MC2R) gene. Induced pluripotent stem cell (iPSC) line SDQLCHi029-A was successfully generated from peripheral blood mononuclear cells obtained from a 5-day-old girl with MC2R mutations (c.428C > T and c.409C > T). The iPSC line showed genetically stable and matched the donor's PBMCs. displayed a normal karyotype, expressed high pluripotent markers, and exhibited differentiation potential of three germ layers in vitro. The iPSC line could be a good model to study the pathogenesis of FGD type 1 and screen new drugs for the disease.

Rare forms of genetic paediatric adrenal insufficiency: Excluding congenital adrenal hyperplasia

Adrenal insufficiency (AI) is a severe endocrine disorder characterized by insufficient glucocorticoid (GC) and/or mineralocorticoid (MC) secretion by the adrenal glands, due to impaired adrenal function (primary adrenal insufficiency, PAI) or to insufficient adrenal stimulation by pituitary ACTH (secondary adrenal insufficiency, SAI) or tertiary adrenal insufficiency due to hypothalamic dysfunction. In this review, we describe rare genetic causes of PAI with isolated GC or combined GC and MC deficiencies and we also describe rare syndromes of isolated MC deficiency. In children, the most frequent cause of PAI is congenital adrenal hyperplasia (CAH), a group of adrenal disorders related to steroidogenic enzyme deficiencies, which will not be included in this review. Less frequently, several rare diseases can cause PAI, either affecting exclusively the adrenal glands or with systemic involvement. The diagnosis of these diseases is often challenging, due to the heterogeneity of their clinical presentation and to their rarity. Therefore, the current review aims to provide an overview on these rare genetic forms of paediatric PAI, offering a review of genetic and clinical features and a summary of diagnostic and therapeutic approaches, promoting awareness among practitioners, and favoring early diagnosis and optimal clinical management in suspect cases.

Growth alterations in rare forms of primary adrenal insufficiency: a neglected issue in paediatric endocrinology

Primary adrenal insufficiency (PAI) is an endocrine disorder characterized by direct adrenal failure^, with consequent glucocorticoid, and eventually mineralocorticoid, deficiency. In children, the main cause of PAI is congenital adrenal hyperplasia (CAH), due to a loss of function of adrenal steroidogenic enzymes, but also rarer forms, including autoimmune polyglandular syndrome, adrenoleucodistrophy, adrenal hypoplasia congenita, familial glucocorticoid deficiency, and Allgrove's Syndrome, may be observed. In PAI children, growth alterations represent a major issue, as both inadequate and excessive glucocorticoid replacement treatment may lead to reduced growth rate and adult height impairment. However, growth abnormalities are poorly studied in rare forms of paediatric PAI, and specific studies on growth rate in these children are currently lacking. In the present review, the currently available evidence on growth alterations in children with rare PAI forms will be summarized, with a major focus on comorbidities with a potential impact on patients' growth rate.

A rare homozygous variant of MC2R gene identified in a Chinese family with familial glucocorticoid deficiency type 1: A case report

Background

Melanocortin-2 receptor (MC2R), a member of the G protein-coupled receptor family, is selectively activated by adrenocorticotropic hormone (ACTH). variants in MC2R are associated with family glucocorticoid deficiency 1 (FGD1).

Case presentation

We first reported a Chinese family with two affected siblings with a homozygotic variant of c.712C>T/p.H238Y in MC2R, presenting with skin hyperpigmentation, hyperbilirubinemia, and tall stature. These individuals showed novel clinical features, including congenital heart defects, not been found in other FGD1 patients.

Conclusions

We reported a Chinese family with affected siblings having a homozygotic variant of c.712C>T/p.H238Y in MC2R.Our report may expand the genetic and clinical spectrum of FGD1.

Adrenal Dysfunction in Mitochondrial Diseases

Cortisol is central to several homeostatic mechanisms including the stress and immune response. Adrenal insufficiency and impaired cortisol production leads to severe, potentially fatal disorders. Several fundamental stages of steroidogenesis occur within the mitochondria. These dynamic organelles not only contribute ATP for steroidogenesis, but also detoxify harmful by-products generated during cortisol synthesis (reactive oxygen species). Mutations in nuclear or mitochondrial DNA that impair mitochondrial function lead to debilitating multi-system diseases. Recently, genetic variants that impair mitochondrial function have been identified in people with isolated cortisol insufficiency. This review aimed to clarify the association between mitochondrial diseases and adrenal insufficiency to produce cortisol. Mitochondrial diseases are rare and mitochondrial diseases that feature adrenal insufficiency are even rarer. We identified only 14 cases of adrenal insufficiency in people with confirmed mitochondrial diseases globally. In line with previous reviews, adrenal dysfunction was most prevalent in mitochondrial deletion syndromes (particularly Pearson syndrome and Kearns-Sayre syndrome) and with point mutations that compromised oxidative phosphorylation. Although adrenal insufficiency has been reported with mitochondrial diseases, the incidence reflects that expected in the general population. Thus, it is unlikely that mitochondrial mutations alone are responsible for an insufficiency to produce cortisol. More research is needed into the pathogenesis of adrenal disease in these individuals.

Structural basis of signaling regulation of the human melanocortin-2 receptor by MRAP1

G protein-coupled receptors (GPCRs) are regulated by various downstream proteins, of which the melanocortin receptor accessory protein 1 (MRAP1) is closely involved in the regulation of melanocortin receptor 2 (MC2R). Assisted by MRAP1, MC2R responds to adrenocorticotropic hormone (ACTH) and stimulates glucocorticoid biogenesis and cortisol secretion. MC2R activation plays an essential role in the hypothalamic-pituitary-adrenal (HPA) axis that regulates stress response, while its dysfunction causes glucocorticoid insufficiency- or cortisol excess-associated disorders. Here, we present a cryo-electron microscopy (cryo-EM) structure of the ACTH-bound MC2R-Gs-MRAP1 complex. Our structure, together with mutagenesis analysis, reveals a unique sharp kink at the extracellular region of MRAP1 and the 'seat-belt' effect of MRAP1 on stabilizing ACTH binding and MC2R activation. Mechanisms of ACTH recognition by MC2R and receptor activation are also demonstrated. These findings deepen our understanding of GPCR regulation by accessory proteins and provide valuable insights into the ab initio design of therapeutic agents targeting MC2R.

Nicotinamide Nucleotide Transhydrogenase (NNT) is essential for adrenal steroidogenesis: clinical and in vitro lessons

BACKGROUND

Nicotinamide nucleotide transhydrogenase (NNT) acts as an antioxidant defense mechanism. NNT mutations cause familial glucocorticoid deficiency (FGD). How impaired oxidative stress disrupts adrenal steroidogenesis remains poorly understood.

OBJECTIVE

To ascertain the role played by NNT in adrenal steroidogenesis.

METHODS

The genotype-phenotype association of a novel pathogenic NNT variant was evaluated in a boy with FGD. Under basal and oxidative stress (OS) induced conditions, transient cell cultures of the patient's and controls wild type (WT) mononuclear blood cells were used to evaluate antioxidant mechanisms and mitochondrial parameters [reactive oxygen species (ROS) production, reduced glutathione (GSH), and mitochondrial mass]. Using CRISPR/Cas9, a stable NNT gene knockdown model was built in H295R adrenocortical carcinoma cells to determine the role played by NNT in mitochondrial parameters and steroidogenesis. NNT immunohistochemistry was assessed in fetal and post-natal human adrenals.

RESULTS

The homozygous NNT p.G866D variant segregated with the FGD phenotype. Under basal and OS conditions, p.G866D homozygous mononuclear blood cells exhibited increased ROS production, and decreased GSH levels and mitochondrial mass when compared to WT NNT cells. In line, H295R NNT knocked-down cells presented impaired NNT protein expression, increased ROS production, decreased the mitochondrial mass, as well as the size and the density of cholesterol lipid droplets. NNT knockdown affected steroidogenic enzyme expression, impairing cortisol and aldosterone secretion. In human adrenals, NNT is abundantly expressed in the transition fetal zone and in zona fasciculata.

CONCLUSION

Together, these studies demonstrate the essential role of NNT in adrenal redox homeostasis and steroidogenesis.

Mitochondrial NAD(P)+ Transhydrogenase: From Molecular Features to Physiology and Disease

Significance: Proton-translocating NAD(P)⁺ transhydrogenase, also known as nicotinamide nucleotide transhydrogenase (NNT), catalyzes a reversible reaction coupling the protonmotive force across the inner mitochondrial membrane and hydride (H^-, a proton plus two electrons) transfer between the mitochondrial pools of NAD(H) and NADP(H). The forward NNT reaction is a source of NADPH in the mitochondrial matrix, fueling antioxidant and biosynthetic pathways with reductive potential. Despite the greater emphasis given to the net forward reaction, the reverse NNT reaction that oxidizes NADPH also occurs in physiological and pathological conditions. Recent Advances: NNT (dys)function has been linked to various metabolic pathways and disease phenotypes. Most of these findings have been based on spontaneous loss-of-function Nnt mutations found in the C57BL/6J mouse strain (Nnt^C57BL/6J mutation) and disease-causing Nnt mutations in humans. The present review focuses on recent advances based on the mouse Nnt^C57BL/6J mutation. Critical Issues: Most studies associating NNT function with disease phenotypes have been based on comparisons between different strains of inbred mice (with or without the Nnt^C57BL/6J mutation), which creates uncertainties over the actual contribution of NNT in the context of other potential genetic modifiers. Future Directions: Future research might contribute to understanding the role of NNT in pathological conditions and elucidate how NNT regulates physiological signaling through its forward and reverse reactions. The importance of NNT in redox balance and tumor cell proliferation makes it a potential target of new therapeutic strategies for oxidative-stress-mediated diseases and cancer. Antioxid. Redox Signal. 36, 864-884.

Long-Term Follow-Up of Three Family Members with a Novel NNT Pathogenic Variant Causing Primary Adrenal Insufficiency

Nicotinamide nucleotide transhydrogenase (NNT) deficiency causes primary adrenal insufficiency (PAI) and possibly some extra-adrenal manifestations. A limited number of these patients were previously described. We present the clinical and genetic characteristics of three family members with a biallelic novel pathogenic variant in the NNT gene. The patients were followed until the ages of 21.6, 20.2, and 4.2 years. PAI was diagnosed in the eldest two brothers after an Addisonian crisis and the third was diagnosed at the age of 4.5 months in the asymptomatic stage due to the genetic screening of family members. Whole exome sequencing with a targeted interpretation of variants in genes related to PAI was performed in all the patients. The urinary steroid metabolome was determined by gas chromatography–mass spectrometry in the asymptomatic patient. The three patients, who were homozygous for c.1575dup in the NNT gene, developed isolated glucocorticoid deficiency. The urinary steroid metabolome showed normal excretion of cortisol metabolites. The adolescent patients had slow pubertal progression with low–normal testicular volume, while testicular endocrine function was normal. Bone mineral density was in the range for osteopenia in both grown-up siblings. Echocardiography revealed no structural or functional heart abnormalities. This article is among the first with a comprehensive and chronologically-detailed description of patients with NNT deficiency.

An Update on Genetics of Adrenal Gland and Associated Disorders

The intricacies of human adrenal development have been under scrutiny for decades. Each year marks the identification of new genes and new interactions between gene products that ultimately will act to produce the fully functioning adult gland. Due to the complexity of this process, genetic missteps may lead to a constellation of pathologies. Recent years have identified several novel genetic causes of adrenal dysgenesis and provided new insights into previously delineated processes. SF1, DAX1 (NR0B1), CDKN1C, SAMD9, GLI3, TPIT, MC2R, MRAP, NNT, TXNRD2, AAAS, and MCM4 are among the genes which have had significant contributions to our understanding of the development and function of both adrenals and gonads. Collection and elucidation of these genetic and clinical insights are valuable tools for clinicians who diagnose and manage cases of adrenal dysfunction.

Diverse etiologies, diagnostic approach, and management of primary adrenal insufficiency in pediatric age

Primary adrenal insufficiency (PAI) in pediatric age is a rare, but potentially fatal condition caused by diverse etiologies including biochemical defects of steroid biosynthesis, developmental abnormalities of the adrenal gland, or reduced responsiveness to adrenocorticotropic hormone. Compared to adult PAI, pediatric PAI is more often the result of genetic (monogenic, syndromic disorders) than acquired conditions. During the past decade, rare monogenic disorders associated with PAI have helped unravel the underlying novel molecular genetic mechanism. The diagnosis of adrenal insufficiency in children and young infancy is often challenging, usually based on clinical suspicion and endocrine laboratory findings. Pediatric endocrinologists sometimes encounter therapeutic difficulty in finding the balance between undertreatment and overtreatment, determining how to optimize the dose over the patient's lifetime, and maximizing mimicry of normal cortisol secretion with glucocorticoid replacement therapy.

Pediatric Primary Adrenal Insufficiency: A 21-year Single Center Experience

OBJECTIVE

Primary adrenal insufficiency (PAI) is a rare but potentially life-threatening condition. In childhood, PAI is usually caused by monogenic diseases. Although congenital adrenal hyperplasia (CAH) is the most common cause of childhood PAI, numerous non-CAH genetic causes have also been identified.

METHODS

Patients aged 0-18 years and diagnosed with PAI between 1998 and 2019 in a tertiary care hospital were retrospectively evaluated. After the etiologic distribution was determined, non-CAH PAI patients were evaluated in detail.

RESULTS

Seventy-three PAI patients were identified. The most common etiology was CAH (69.9%, n=51). Non-CAH etiologies accounted for 30.1% (n=22) and included adrenoleukodystrophy (ALD; n=8), familial glucocorticoid deficiency (n=3), Triple A syndrome (n=5), autoimmune adrenalitis (n=1), adrenal hypoplasia congenital (n=1), IMAGe syndrome (n=1), and other unknown etiologies (n=3). The median age at the time of AI diagnosis for non-CAH etiologies was 3.52 (0.03-15.17) years. The most frequent symptoms/clinical findings at onset were hyperpigmentation of skin (81.8%), symptoms of hypoglycemia (40.9%), and weakness/fatigue (31.8%). Hypoglycemia (50.0%), hyponatremia (36.4%) and hyperkalemia (22.7%) were prominent biochemical findings. Diagnosis of specific etiologies were proven genetically in 13 of 22 patients. A novel p.Q301* hemizygous frameshift mutation of the DAX1 gene was identified in one patient.

CONCLUSION

Etiology was determined in 86.3% of children with non-CAH PAI through specific clinical and laboratory findings with/ without molecular analysis of candidate genes. ALD was the most common etiology. Currently, advanced molecular analysis can be utilized to establish a specific genetic diagnosis for PAI in patients who have no specific diagnostic features.

Mylk3 null C57BL/6N mice develop cardiomyopathy, whereas Nnt null C57BL/6J mice do not

The C57BL/6J and C57BL/6N mice have well-documented phenotypic and genotypic differences, including the infamous nicotinamide nucleotide transhydrogenase (Nnt) null mutation in the C57BL/6J substrain, which has been linked to cardiovascular traits in mice and cardiomyopathy in humans. To assess whether Nnt loss alone causes a cardiovascular phenotype, we investigated the C57BL/6N, C57BL/6J mice and a C57BL/6J-BAC transgenic rescuing NNT expression, at 3, 12, and 18 mo. We identified a modest dilated cardiomyopathy in the C57BL/6N mice, absent in the two B6J substrains. Immunofluorescent staining of cardiomyocytes revealed eccentric hypertrophy in these mice, with defects in sarcomere organisation. RNAseq analysis identified differential expression of a number of cardiac remodelling genes commonly associated with cardiac disease segregating with the phenotype. Variant calling from RNAseq data identified a myosin light chain kinase 3 (Mylk3) mutation in C57BL/6N mice, which abolishes MYLK3 protein expression. These results indicate the C57BL/6J Nnt-null mice do not develop cardiomyopathy; however, we identified a null mutation in Mylk3 as a credible cause of the cardiomyopathy phenotype in the C57BL/6N.

Molecular determinants of ACTH receptor for ligand selectivity

The adrenocorticotropic hormone (ACTH) receptor, known as the melanocortin-2 receptor (MC2R), plays a key role in regulating adrenocortical function. ACTH receptor is a subtype of the melanocortin receptor family which is a member of the G-protein coupled receptor (GPCR) superfamily. ACTH receptor has unique characteristics among MCRs. α-MSH, β-MSH, γ-MSH and ACTH are agonists for MCRs but only ACTH is the agonist for ACTH receptor. In addition, the melanocortin receptor accessory protein (MRAP) is required for ACTH receptor expression at cell surface and function. In this review, we summarized the information available on the relationship between ACTH and ACTH receptor and provide the latest understanding of the molecular basis of the ACTH receptor responsible for ligand selectivity and function.

Abnormal linear growth in paediatric adrenal diseases: Pathogenesis, prevalence and management

Abnormal adrenal function can interfere with linear growth, potentially causing either acceleration or impairment of growth in paediatric patients. These abnormalities can be caused by direct effects of adrenal hormones, particularly glucocorticoids and sex steroids, or be mediated by indirect mechanisms such as the disturbance of the growth hormone-insulin-like growth factor-1 axis and aromatization of androgens to oestrogens. The early diagnosis and optimal treatment of adrenal disorders can prevent or minimize growth disturbance and facilitate improved height gain. Mechanisms of growth disturbance in the following abnormal states will be discussed; hypercortisolaemia, hyperandrogenaemia and obesity. Prevalence and features of growth disturbance will be discussed in ACTH-dependent and ACTH-independent Cushing's syndrome, adrenocortical tumours, premature adrenarche, congenital adrenal hyperplasia and adrenal insufficiency disorders. Recommendations for management have been included.

Familial glucocorticoid deficiency presenting with hyperpigmentation, gigantism, and motor development delay: a case report

Background

Familial glucocorticoid deficiency is a rare autosomal recessive disorder characterized by isolated glucocorticoid deficiency. Most patients are diagnosed following episodes of hypoglycemia or convulsion. We report the case of an infant with familial glucocorticoid deficiency who presented with hyperpigmentation, gigantism, and motor developmental delay without documented hypoglycemia, convulsion, or circulatory collapse.

Case presentation

A 10-month-old Sri Lankan Sinhalese baby boy born to consanguineous parents presented with generalized hyperpigmentation and overgrowth since birth. He had marginal gross motor developmental delay. His weight, length, and head circumference were above normal range for his age. Investigations revealed low serum cortisol and high adrenocorticotrophic hormone levels with no cortisol response following adrenocorticotropin stimulation. Serum electrolytes and aldosterone levels were normal. A diagnosis of familial glucocorticoid deficiency was made based on isolated glucocorticoid deficiency, hyperpigmentation, and tall stature.

Conclusions

This case report highlights that glucocorticoid deficiency can present without documented hypoglycemia and circulatory collapse and a high degree of suspicion is needed in diagnosis.

Primary Cortisol Deficiency and Growth Hormone Deficiency in a Neonate With Hypoglycemia: Coincidence or Consequence?

Cortisol and growth hormone (GH) deficiencies are causes of neonatal hypoglycemia. When they coexist, a pituitary disorder is suspected. We present an infant with hypoglycemia in whom an ACTH receptor defect was associated with transient GH deficiency. A full-term boy with consanguineous parents presented with hypoglycemia (serum glucose 18 mg/dL) at 4 hours of life with undetectable serum cortisol (<1 μg/dL). Examination showed diffuse hyperpigmentation with normal male genitalia. Patient developed hyperbilirubinemia and elevated transaminase levels. GH levels of 6.8 ng/mL and 7.48 ng/mL during episodes of hypoglycemia, peak of 9.2 ng/mL with glucagon stimulation, and undetectable IGF-1 suggested GH deficiency. Thyroid function, prolactin, and gonadotropins were normal. Baseline ACTH was elevated at 4868 pg/mL, whereas serum cortisol remained undetectable with ACTH stimulation. Hydrocortisone replacement resulted in normalization of blood glucose and cholestasis with decline in ACTH level. GH therapy was not initiated, given improvement in cholestasis and euglycemia. An ACTH receptor defect was confirmed with molecular genetic testing that revealed homozygosity for a known mutation of the melanocortin 2 receptor (MC2R) gene. At 12 weeks, a random GH level was 10 ng/mL. IGF-1 was 75 ng/mL and 101 ng/mL at 7 and 9 months, respectively. This report describes glucocorticoid deficiency from an MC2R mutation associated with GH deficiency. With glucocorticoid replacement, GH secretion normalized. Our findings are consistent with a previously stated hypothesis that physiologic glucocorticoid levels may be required for optimal GH secretion [1].

Steroidogenic differentiation and PKA signaling are programmed by histone methyltransferase EZH2 in the adrenal cortex

Adrenal cortex steroids are essential for body homeostasis, and adrenal insufficiency is a life-threatening condition. Adrenal endocrine activity is maintained through recruitment of subcapsular progenitor cells that follow a unidirectional differentiation path from zona glomerulosa to zona fasciculata (zF). Here, we show that this unidirectionality is ensured by the histone methyltransferase EZH2. Indeed, we demonstrate that EZH2 maintains adrenal steroidogenic cell differentiation by preventing expression of GATA4 and WT1 that cause abnormal dedifferentiation to a progenitor-like state in Ezh2 KO adrenals. EZH2 further ensures normal cortical differentiation by programming cells for optimal response to adrenocorticotrophic hormone (ACTH)/PKA signaling. This is achieved by repression of phosphodiesterases PDE1B, 3A, and 7A and of PRKAR1B. Consequently, EZH2 ablation results in blunted zF differentiation and primary glucocorticoid insufficiency. These data demonstrate an all-encompassing role for EZH2 in programming steroidogenic cells for optimal response to differentiation signals and in maintaining their differentiated state.

Mitochondrial Antioxidants and the Maintenance of Cellular Hydrogen Peroxide Levels

For over 40 years, mitochondrial reactive oxygen species (ROS) production and balance has been studied in the context of oxidative distress and tissue damage. However, research over the past decade has demonstrated that the mitochondria have a more complicated relationship with ROS. Superoxide (O₂^•-) and hydrogen peroxide (H₂O₂) are the proximal ROS formed by the mitochondria, and the latter molecule is used as a secondary messenger to coordinate oxidative metabolism with changes in cell physiology. Like any other secondary messenger, H₂O₂ levels need to be regulated through its production and degradation and the mitochondria are enriched with the antioxidant defenses required to degrade ROS formed by nutrient oxidation and respiration. Recent work has also demonstrated that these antioxidant systems also carry the capacity to clear H₂O₂ formed outside of mitochondria. These observations led to the development of the postulate that the mitochondria serve as "ROS stabilizing devices" that buffer cellular H₂O₂ levels. Here, I provide an updated view on mitochondrial ROS homeostasis and discuss the "ROS stabilizing" function of the mitochondria in mammalian cells. This will be followed by a hypothetical discussion on the potential function of the mitochondria and proton motive force in degrading cellular H₂O₂ signals emanating from cytosolic enzymes.

An energetic view of stress: Focus on mitochondria

Energy is required to sustain life and enable stress adaptation. At the cellular level, energy is largely derived from mitochondria - unique multifunctional organelles with their own genome. Four main elements connect mitochondria to stress: (1) Energy is required at the molecular, (epi)genetic, cellular, organellar, and systemic levels to sustain components of stress responses; (2) Glucocorticoids and other steroid hormones are produced and metabolized by mitochondria; (3) Reciprocally, mitochondria respond to neuroendocrine and metabolic stress mediators; and (4) Experimentally manipulating mitochondrial functions alters physiological and behavioral responses to psychological stress. Thus, mitochondria are endocrine organelles that provide both the energy and signals that enable and direct stress adaptation. Neural circuits regulating social behavior - as well as psychopathological processes - are also influenced by mitochondrial energetics. An integrative view of stress as an energy-driven process opens new opportunities to study mechanisms of adaptation and regulation across the lifespan.

Diseases Associated with Mutation of Replication and Repair Proteins

Alterations in proteins that function in DNA replication and repair have been implicated in the development of human diseases including cancer, premature ageing, skeletal disorders, mental retardation, microcephaly, and neurodegeneration. Drosophila has orthologues of most human replication and repair proteins and high conservation of the relevant cellular pathways, thus providing a versatile system in which to study how these pathways are corrupted leading to the diseased state. In this chapter I will briefly review the diseases associated with defects in replication and repair proteins and discuss how past and future studies on the Drosophila orthologues of such proteins can contribute to the dissection of the mechanisms involved in disease development.

MECHANISMS IN ENDOCRINOLOGY: Update on pathogenesis of primary adrenal insufficiency: beyond steroid enzyme deficiency and autoimmune adrenal destruction

Primary adrenal insufficiency (PAI) is potentially life threatening, but rare. In children, genetic defects prevail whereas adults suffer more often from acquired forms of PAI. The spectrum of genetic defects has increased in recent years with the use of next-generation sequencing methods and now has reached far beyond genetic defects in all known enzymes of adrenal steroidogenesis. Cofactor disorders such as P450 oxidoreductase (POR) deficiency manifesting as a complex form of congenital adrenal hyperplasia with a broad clinical phenotype have come to the fore. In patients with isolated familial glucocorticoid deficiency (FGD), in which no mutations in the genes for the ACTH receptor (MC2R) or its accessory protein MRAP have been found, non-classic steroidogenic acute regulatory protein (StAR) and CYP11A1 mutations have been described; and more recently novel mutations in genes such as nicotinamide nucleotide transhydrogenase (NNT) and thioredoxin reductase 2 (TRXR2) involved in the maintenance of the mitochondrial redox potential and generation of NADPH important for steroidogenesis and ROS detoxication have been discovered. In addition, whole exome sequencing approach also solved the genetics of some syndromic forms of PAI including IMAGe syndrome (CDKN1C), Irish traveler syndrome (MCM4), MIRAGE syndrome (SAMD9); and most recently a syndrome combining FGD with steroid-resistant nephrotic syndrome and ichthyosis caused by mutations in the gene for sphingosine-1-phosphate lyase 1 (SGPL1). This review intends do give an update on novel genetic forms of PAI and their suggested mechanism of disease. It also advocates for advanced genetic work-up of PAI (especially in children) to reach a specific diagnosis for better counseling and treatment.

Early diagnosis in familial glucocorticoid deficiency

Familial glucocorticoid deficiency (FGD) is a rare autosomal recessive condition, characterized by marked atrophy of zona fasiculata and reticalaris with preservation of zona glomerulosa. Out of more than 50 published cases, 18 patients died as a result of glucocorticoid insufficiency. The main objective of this report is to emphasize the early diagnosis and treatment in our 17 month-old patient. Her presenting features following an upper respiratory tract infection were hypoglycemia, seizures as well as deep hyperpigmentation of the limbs and lips. A low cortisol concentration, elevated ACTH level and normal electrolytes and aldosterone level all supported the diagnosis of primary glucocorticoid deficiency. Parents were counseled about the diagnosis, management and the lifelong requirement of steroids. FGD is an easily treatable disease when recognized but frequently missed due to a non-specific presentation. FGD is a treatable disease, delayed diagnosis and treatment can lead to significant morbidity.

A Pilot Study Evaluating Therapeutic Response of Different Dosage of Oral Glucocorticoid in Two Children with Familial Glucocorticoid Deficiency Presenting with Diffuse Mucocutaneous Hyperpigmentation

INTRODUCTION

Familial glucocorticoid deficiency (FGD) is a rare autosomal recessive potentially life-threatening condition, characterized by glucocorticoid deficiency, preserved aldosterone/renin secretion, and secondary rise in plasma adrenocorticotropic hormone level. This occurs due to either mutation in adrenocorticotropic receptor (25%, FGD Type-1) or in the MC2 receptor accessory protein (15%-20%). However, in about 50% patients, no identifiable mutations have been identified. Clinically, it manifests with weakness, fatigue, weight loss, anorexia, nausea, vomiting, diarrhea, abdominal pain, hypoglycemia, and hypothermia. Progressive mucocutaneous pigmentation is a conspicuous presentation. Repeated hypoglycemia may result in seizure, persistent neurological, severe mental disability, and even sudden death. Standard therapy is oral glucocorticoids (10-15 mg/m²).

PATIENTS AND RESULTS

Two familial cases of FGD were put on progressively increasing doses of oral glucocorticoids (10 mg, 15 mg, and 20 mg/m²/day, each for 6 weeks) to achieve the best response without any adverse effects. One patient had excellent improvement with 15 mg/m²/day, and another required 20 mg/m²/day. The latter patient had excellent overall improvement with only moderate improvement in pigmentation.

CONCLUSION

Glucocorticoids replacement with optimum dose is necessary in FGD to promote physical and neurological growth and to prevent adrenal crises, hypotension, hypoglycemia, and sudden death. Higher dose than mentioned in literature (15 mg/m²/day) may be required in selected cases. Mucocutaneous pigmentation may require even higher dose than we used. More studies are required.

ACTH Receptor (MC2R) Specificity: What Do We Know About Underlying Molecular Mechanisms?

Coincidentally, the release of this Research Topic in Frontiers in Endocrinology takes place 25 years after the discovery of the adrenocorticotropic hormone receptor (ACTHR) by Mountjoy and colleagues. In subsequent years, following the discovery of other types of mammalian melanocortin receptors (MCRs), ACTHR also became known as melanocortin type 2 receptor (MC2R). At present, five types of MCRs have been reported, all of which share significant sequence similarity at the amino acid level, and all of which specifically bind melanocortins (MCs)-a group of biologically active peptides generated by proteolysis of the proopiomelanocortin precursor. All MCs share an identical -H-F-R-W- pharmacophore sequence. α-Melanocyte-stimulating hormone (α-MSH) and adrenocorticotropic hormone (ACTH) are the most extensively studied MCs and are derived from the same region. Essentially, α-MSH is formed from the first 13 amino acid residues of ACTH. ACTHR is unique among MCRs because it binds one sole ligand-ACTH, which makes it a very attractive research object for molecular pharmacologists. However, much research has failed, and functional studies of this receptor are lagging behind other MCRs. The reason for these difficulties has already been outlined by Mountjoy and colleagues in their publication on ACTHR coding sequence discovery where the Cloudman S91 melanoma cell line was used for receptor expression because it was a "more sensitive assay system." Subsequent work showed that ACTHR could be successfully expressed only in endogenous MCR-expressing cell lines, since in other cell lines it is retained within the endoplasmic reticulum. The resolution of this methodological problem came in 2005 with the discovery of melanocortin receptor accessory protein, which is required for the formation of functionally active ACTHR. The decade that followed this discovery was filled with exciting research that provided insight into the molecular mechanisms underlying the action of ACTHR. The purpose of this review is to summarize the advances in this fascinating research field.

From Bioinactive ACTH to ACTH Antagonist: The Clinical Perspective

The adrenocorticotropic hormone (ACTH) is a pituitary hormone derived from a larger peptide, the proopiomelanocortin (POMC), as are the MSHs (α-MSH, β-MSH, and γ-MSH) and the β-LPH-related polypeptides (Figure 1A). ACTH drives adrenal steroidogenesis and growth of the adrenal gland. ACTH is a 39 amino acid polypeptide that binds and activates its cognate receptor [melanocortin receptor 2 (MC2R)] through the two regions H₆F₇R₈W₉ and K₁₅K₁₆R₁₇R₁₈P₁₉. Most POMC-derived polypeptides contain the H₆F₇R₈W₉ sequence that is conserved through evolution. This explains the difficulties in developing selective agonists or antagonists to the MCRs. In this review, we will discuss the clinical aspects of the role of ACTH in physiology and disease, and potential clinical use of selective ACTH antagonists.

Neonatal presentation of familial glucocorticoid deficiency with a MRAP mutation: A case report

Familial glucocorticoid deficiency (FGD) is a rare autosomal recessive disorder in which the adrenal cortex fails to respond appropriately to stimulation by adrenocorticotropic hormone (ACTH) to produce cortisol. The disease is characterized in laboratory testing by glucocorticoid deficiency and markedly elevated ACTH levels. FGD may present in infancy or early childhood with symptoms related to low cortisol and high ACTH, such as hyperpigmentation, severe hypoglycemia, failure to thrive and recurrent infections. Mutations in the MC2R accessory protein (MRAP) cause FGD types 2, which accounts for approximately 15–20% of FGD cases. Here, we report a female neonate of Chinese Han origin, who presented with noted hyperpigmentation at birth. Laboratory investigations revealed hypocortisolaemia (cortisol < 1.0 μg/dl) and elevated plasma ACTH (1051 pg/ml). She responded to hydrocortisone treatment. Genetic studies confirmed the diagnosis showing homozygous deletion (c. 106 + 1delG) in intron 3 of MRAP gene, a mutation already reported as responsible for FDG type 2. This mutation can cause complete lack of ACTH response thus explaining the early presentation in this case. Her parents and maternal grandmother were heterozygous for the same mutation. To our knowledge, this is the first Chinese Han patient reported with FGD type 2 due to a known MRAP mutation.

Congenital primary adrenal insufficiency and selective aldosterone defects presenting as salt-wasting in infancy: a single center 10-year experience

Background

Salt-wasting represents a relatively common cause of emergency admission in infants and may result in life-threatening complications. Neonatal kidneys show low glomerular filtration rate and immaturity of the distal nephron leading to reduced ability to concentrate urine.

Methods

A retrospective chart review was conducted for infants hospitalized in a single Institution from 1^st January 2006 to 31^st December 2015. The selection criterion was represented by the referral to the Endocrinology Unit for hyponatremia (serum sodium <130 mEq/L) of suspected endocrine origin at admission.

Results

Fifty-one infants were identified. In nine infants (17.6 %) hyponatremia was related to unrecognized chronic gastrointestinal or renal salt losses or reduced sodium intake. In 10 infants (19.6 %) hyponatremia was related to central nervous system diseases. In 19 patients (37.3 %) the final diagnosis was congenital adrenal hyperplasia (CAH). CAH was related to 21-hydroxylase deficiency in 18 patients, and to 3β-Hydroxysteroid dehydrogenase (3βHSD) deficiency in one patient. Thirteen patients (25.5 %) were affected by different non-CAH salt-wasting forms of adrenal origin. Four familial cases of X-linked adrenal hypoplasia congenita due to NROB1 gene mutation were identified. Two unrelated girls showed aldosterone synthase deficiency due to mutation of the CYP11B2 gene. Two unrelated infants were affected by familial glucocorticoid deficiency due to MC2R gene mutations. One girl showed pseudohypoaldosteronism related to mutations of the SCNN1G gene encoding for the epithelial sodium channel. Transient pseudohypoaldosteronism was identified in two patients with renal malformations. In two infants the genetic aetiology was not identified.

Conclusions

Emergency management of infants presenting with salt wasting requires correction of water losses and treatment of electrolyte imbalances. Nevertheless, the differential diagnosis may be difficult in emergency settings, and sometimes hospitalized infants presenting with salt-wasting are immediately started on steroid therapy to avoid life-threatening complications, before the correct diagnosis is reached. Physicians involved in the management of infants with salt-wasting of suspected hormonal origin should remember that, whenever practicable, a blood sample for the essential hormonal investigations should be collected before starting steroid therapy, to guide the subsequent diagnostic procedures and in particular to address the analysis of candidate genes.

Diagnosis and management of pediatric adrenal insufficiency

BACKGROUND

Adrenal insufficiency (AI) is a wellknown cause of potentially life-threatening disorders. Defects at each level of the hypothalamic-pituitary-adrenal axis can impair adrenal function, leading to varying degrees of glucocorticoid (GC) deficiency. Iatrogenic AI induced by exogenous GCs is the most common cause of AI. The criteria for the diagnosis and management of iatrogenic AI, neonatal AI, and critical illness-related corticosteroid insufficiency (CIRCI) are not clear.

DATA SOURCES

We reviewed the recent original publications and classical data from the literature, as well as the clinical, diagnostic and management strategies of pediatric AI.

RESULTS

Practical points in the diagnosis and management of AI with an emphasis on iatrogenic AI, neonatal AI, and CIRCI are provided. Given the lack of sensitive and practical biochemical tests for diagnosis of subtle AI, GC treatment has to be tailored to highly suggestive clinical symptoms and signs. Treatment of adrenal crisis is well standardized and patients almost invariably respond well to therapy. It is mainly the delay in treatment that is responsible for mortality in adrenal crisis.

CONCLUSIONS

Education of patients and health care professionals is mandatory for timely interventions for patients with adrenal crisis.

60 YEARS OF POMC: Adrenal and extra-adrenal functions of ACTH

The pituitary adrenocorticotropic hormone (ACTH) plays a pivotal role in homeostasis and stress response and is thus the major component of the hypothalamo-pituitary-adrenal axis. After a brief summary of ACTH production from proopiomelanocortin (POMC) and on ACTH receptor properties, the first part of the review covers the role of ACTH in steroidogenesis and steroid secretion. We highlight the mechanisms explaining the differential acute vs chronic effects of ACTH on aldosterone and glucocorticoid secretion. The second part summarizes the effects of ACTH on adrenal growth, addressing its role as either a mitogenic or a differentiating factor. We then review the mechanisms involved in steroid secretion, from the classical Cyclic adenosine monophosphate second messenger system to various signaling cascades. We also consider how the interaction between the extracellular matrix and the cytoskeleton may trigger activation of signaling platforms potentially stimulating or repressing the steroidogenic potency of ACTH. Finally, we consider the extra-adrenal actions of ACTH, in particular its role in differentiation in a variety of cell types, in addition to its known lipolytic effects on adipocytes. In each section, we endeavor to correlate basic mechanisms of ACTH function with the pathological consequences of ACTH signaling deficiency and of overproduction of ACTH.

Rare Causes of Primary Adrenal Insufficiency: Genetic and Clinical Characterization of a Large Nationwide Cohort

CONTEXT

Primary adrenal insufficiency (PAI) is a life-threatening condition that is often due to monogenic causes in children. Although congenital adrenal hyperplasia occurs commonly, several other important molecular causes have been reported, often with overlapping clinical and biochemical features. The relative prevalence of these conditions is not known, but making a specific diagnosis can have important implications for management.

OBJECTIVE

The objective of the study was to investigate the clinical and molecular genetic characteristics of a nationwide cohort of children with PAI of unknown etiology.

DESIGN

A structured questionnaire was used to evaluate clinical, biochemical, and imaging data. Genetic analysis was performed using Haloplex capture and next-generation sequencing. Patients with congenital adrenal hyperplasia, adrenoleukodystrophy, autoimmune adrenal insufficiency, or obvious syndromic PAI were excluded.

SETTING

The study was conducted in 19 tertiary pediatric endocrinology clinics.

PATIENTS

Ninety-five children (48 females, aged 0-18 y, eight familial) with PAI of unknown etiology participated in the study.

RESULTS

A genetic diagnosis was obtained in 77 patients (81%). The range of etiologies was as follows: MC2R (n = 25), NR0B1 (n = 12), STAR (n = 11), CYP11A1 (n = 9), MRAP (n = 9), NNT (n = 7), ABCD1 (n = 2), NR5A1 (n = 1), and AAAS (n = 1). Recurrent mutations occurred in several genes, such as c.560delT in MC2R, p.R451W in CYP11A1, and c.IVS3ds+1delG in MRAP. Several important clinical and molecular insights emerged.

CONCLUSION

This is the largest nationwide study of the molecular genetics of childhood PAI undertaken. Achieving a molecular diagnosis in more than 80% of children has important translational impact for counseling families, presymptomatic diagnosis, personalized treatment (eg, mineralocorticoid replacement), predicting comorbidities (eg, neurological, puberty/fertility), and targeting clinical genetic testing in the future.

Primary Adrenocortical Insufficiency Case Series: Genetic Etiologies More Common than Expected

BACKGROUND/AIMS

Primary adrenal insufficiency (AI) is an important cause of morbidity in children. Our objectives were: (1) to describe the clinical presentation of children with new-onset primary AI, and (2) to identify monogenic causes of primary AI in children.

METHODS

Chart review and mutation detection in candidate genes were conducted for 11 patients with primary AI.

RESULTS

The likely cause of AI was determined in 9 patients. One had a homozygous MC2R mutation associated with familial glucocorticoid deficiency. Two had the same homozygous mutation in the AIRE gene which is associated with type 1 autoimmune polyglandular syndrome. One patient had a heterozygous change in this gene of undetermined significance. Five were homozygous for the previously reported p.R188C STAR mutation causing nonclassic lipoid congenital adrenal hyperplasia, representing the largest cohort of such patients from a single geographic area. In the remaining 2 patients, no clear etiology was identified.

CONCLUSIONS

We recommend genetic testing for patients who have negative anti-adrenal antibodies or suggestive family history. Diagnosing a genetic etiology can provide information about prognosis and treatment, and is therefore beneficial for patients. Our high proportion of patients with nonclassic lipoid congenital adrenal hyperplasia likely represents a founder effect.

Insights from exome sequencing for endocrine disorders

Whole-exome sequencing has emerged as a fast and effective tool for the elucidation of genetic defects underlying both rare and common human diseases. Increased availability and decreased costs of next-generation sequencing have enabled investigators to use this approach not only in individual patients with rare diseases, but also to screen large cohorts or populations for the genetic determinants of diseases. Within the field of endocrinology, exome sequencing has led to major advancements in our understanding of many disorders including adrenal disease, growth and puberty disorders and type 2 diabetes mellitus, as well as a multitude of rare genetic syndromes with prominent endocrine involvement. In this Review, we provide an overview of these new insights and discuss the role that exome sequencing is expected to have in endocrine research and future clinical practice.

Adrenal cortex tissue homeostasis and zonation: A WNT perspective

The adrenal cortex plays essential roles in the control of sodium and water homeostasis, stress response, inflammation and metabolism, through secretion of glucocorticoids and mineralocorticoids. Coordinated production of these hormones relies on functional zonation of the cortex, characterised by expression of Cyp11b2 under the control of angiotensin II and plasma potassium level in zona glomerulosa (ZG) and Cyp11b1 under the control of ACTH in zona fasciculata (ZF). The mechanisms involved in the establishment of functional zonation and its maintenance during centripetal cortex cell renewal are still poorly understood. Here, we hypothesise that the hormonal and signalling pathways that control adrenal cortex function are also involved in cortical zonation. In particular, we summarise evidence on the role of WNT/β-catenin signalling in ZG differentiation and how tight control of its activity is required to shape the adult cortex. In this context, we discuss the potential role of known WNT regulators and the possibility of a reciprocal cross-talk between PKA and WNT signalling.

Combined mineralocorticoid and glucocorticoid deficiency is caused by a novel founder nicotinamide nucleotide transhydrogenase mutation that alters mitochondrial morphology and increases oxidative stress

Background

Familial glucocorticoid deficiency (FGD) reflects specific failure of adrenocortical glucocorticoid production in response to adrenocorticotropic hormone (ACTH). Most cases are caused by mutations encoding ACTH-receptor components (MC2R, MRAP) or the general steroidogenesis protein (StAR). Recently, nicotinamide nucleotide transhydrogenase (NNT) mutations were found to cause FGD through a postulated mechanism resulting from decreased detoxification of reactive oxygen species (ROS) in adrenocortical cells.

Methods and results

In a consanguineous Palestinian family with combined mineralocorticoid and glucocorticoid deficiency, whole-exome sequencing revealed a novel homozygous NNT_c.598 G>A, p.G200S, mutation. Another affected, unrelated Palestinian child was also homozygous for NNT_p.G200S. Haplotype analysis showed this mutation is ancestral; carrier frequency in ethnically matched controls is 1/200. Assessment of patient fibroblasts for ROS production, ATP content and mitochondrial morphology showed that biallelic NNT mutations result in increased levels of ROS, lower ATP content and morphological mitochondrial defects.

Conclusions

This report of a novel NNT mutation, p.G200S, expands the phenotype of NNT mutations to include mineralocorticoid deficiency. We provide the first patient-based evidence that NNT mutations can cause oxidative stress and both phenotypic and functional mitochondrial defects. These results directly demonstrate the importance of NNT to mitochondrial function in the setting of adrenocortical insufficiency.

Impact of a novel homozygous mutation in nicotinamide nucleotide transhydrogenase on mitochondrial DNA integrity in a case of familial glucocorticoid deficiency

BACKGROUND

Familial Glucocorticoid Deficiency (FGD) is a rare autosomal recessive disorder that is characterized by isolated glucocorticoid deficiency. Recently, mutations in the gene encoding for the mitochondrial nicotinamide nucleotide transhydrogenase (NNT) have been identified as a causative gene for FGD; however, no NNT activities have been reported in FGD patients carrying NNT mutations.

METHODS

Clinical, biochemical and molecular analyses of lymphocytes from FDG homozygous and heterozygous carriers for the F215S NNT mutation.

RESULTS

In this study, we described an FGD-affected Japanese patient carrying a novel NNT homozygous mutation (c.644T>C; F215S) with a significant loss-of-function (NNT activity = 31% of healthy controls) in peripheral blood cells' mitochondria. The NNT activities of the parents, heterozygous for the mutation, were 61% of controls.

CONCLUSIONS

Our results indicated that (i) mitochondrial biogenesis (citrate synthase activity) and/or mtDNA replication (mtDNA copy number) were affected at ≤60% NNT activity because these parameters were affected in individuals carrying either one or both mutated alleles; and (ii) other outcomes (mtDNA deletions, protein tyrosine nitration, OXPHOS capacity) were affected at ≤30% NNT activity as also observed in murine cerebellar mitochondria from C57BL/6J (NNT^-/-) vs. C57BL/6JN (NNT^+/+) substrains.

GENERAL SIGNIFICANCE

By studying a family affected with a novel point mutation in the NNT gene, a gene-dose response was found for various mitochondrial outcomes providing for novel insights into the role of NNT in the maintenance of mtDNA integrity beyond that described for preventing oxidative stress.

Novel insight into etiology, diagnosis and management of primary adrenal insufficiency

Primary adrenal insufficiency (PAI) is a rare condition in childhood which is either inherited (mostly) or acquired. It is characterized by glucocorticoid and maybe mineralocorticoid deficiency. The most common form in children is 21-hydroxylase deficiency, which belongs to the steroid biosynthetic defects causing PAI. Newer forms of complex defects of steroid biosynthesis are P450 oxidoreductase deficiency and (apparent) cortisone reductase deficiency. Other forms of PAI include metabolic disorders, autoimmune disorders and adrenal dysgenesis, e.g. the IMAGe syndrome, for which the underlying genetic defect has been recently identified. Newer work has also expanded the genetic causes underlying isolated, familial glucocorticoid deficiency (FGD). Mild mutations of CYP11A1 or StAR have been identified in patients with FGD. MCM4 mutations were found in a variant of FGD in an Irish travelling community manifesting with PAI, short stature, microcephaly and recurrent infections. Finally, mutations in genes involved in the detoxification of reactive oxygen species were identified in patients with unsolved FGD. Most mutations were found in the enzyme nicotinamide nucleotide transhydrogenase, which uses the mitochondrial proton pump gradient to produce NADPH. NADPH is essential in maintaining high levels of reduced forms of antioxidant enzymes for the reduction of hydrogen peroxide. Similarly, mutations in the gene for TXNRD2 involved in this system were found in FGD patients, suggesting that the adrenal cortex is particularly susceptible to oxidative stress.

Genetic forms of adrenal insufficiency

OBJECTIVE

The American Association of Clinical Endocrinologists Adrenal Scientific Committee has developed a series of articles to update members on the genetics of adrenal diseases.

METHODS

Case presentation, discussion of literature, table, and bullet point conclusions.

RESULTS

The genetic mutations associated with several familial causes of adrenal insufficiency have now been identified. The most common ones that will be discussed here include Allgrove syndrome, adrenoleukodystrophy, adrenal hypoplasia congenita, autoimmune polyglandular syndrome type 1, congenital adrenal hyperplasia (CAH), lipoid CAH, and familial glucocorticoid deficiency. Although these diseases most commonly present in childhood, some rarely present in adulthood, and thus all endocrinologists must be familiar with these syndromes. Some patients only develop glucocorticoid deficiency, and others have both glucocorticoid and mineralocorticoid deficiency. These diseases may be associated with other conditions, especially neurologic disease, hypogonadism, or dermatologic problems. Diagnosis is suspected based on clinical presentation and laboratory findings. Gene testing may be necessary for confirmation of a diagnosis and/or screening of family members.

CONCLUSION

This article briefly reviews the various familial adrenal insufficiency syndromes and the specific associated gene defects.

NNT pseudoexon activation as a novel mechanism for disease in two siblings with familial glucocorticoid deficiency

CONTEXT

Intronic DNA frequently encodes potential exonic sequences called pseudoexons. In recent years, mutations resulting in aberrant pseudoexon inclusion have been increasingly recognized to cause disease.

OBJECTIVES

To find the genetic cause of familial glucocorticoid deficiency (FGD) in two siblings.

PATIENTS

The proband and his affected sibling, from nonconsanguineous parents of East Asian and South African origin, were diagnosed with FGD at the ages of 21 and 8 months, respectively.

DESIGN

Whole exome sequencing was performed on genomic DNA (gDNA) of the siblings. Variants in genes known to cause FGD were assessed for causality. Further analysis of gDNA and cDNA was performed by PCR/RT-PCR followed by automated Sanger sequencing.

RESULTS

Whole exome sequencing identified a single, novel heterozygous variant (p.Arg71*) in nicotinamide nucleotide transhydrogenase (NNT) in both affected individuals. Follow-up cDNA analysis in the proband identified a 69-bp pseudoexon inclusion event, and Sanger sequencing of his gDNA identified a 4-bp duplication responsible for its activation. The variants segregated with the disease: p.Arg71* was inherited from the mother, the pseudoexon change was inherited from the father, and an unaffected sibling had inherited only the p.Arg71* variant.

CONCLUSIONS

FGD in these siblings is caused by compound heterozygous mutations in NNT; one causing pseudoexon inclusion in combination with another leading to Arg71*. Discovery of this pseudoexon activation mutation highlights the importance of identifying sequence changes in introns by cDNA analysis. The clinical implications of these findings include: facilitation of antenatal genetic diagnosis, early institution of potentially lifesaving therapy, and the possibility of preventative or curative intervention.

Adrenocortical growth and cancer

The adrenal gland consists of two distinct parts, the cortex and the medulla. Molecular mechanisms controlling differentiation and growth of the adrenal gland have been studied in detail using mouse models. Knowledge also came from investigations of genetic disorders altering adrenal development and/or function. During embryonic development, the adrenal cortex acquires a structural and functional zonation in which the adrenal cortex is divided into three different steroidogenic zones. Significant progress has been made in understanding adrenal zonation. Recent lineage tracing experiments have accumulated evidence for a centripetal differentiation of adrenocortical cells from the subcapsular area to the inner part of the adrenal cortex. Understanding of the mechanism of adrenocortical cancer (ACC) development was stimulated by knowledge of adrenal gland development. ACC is a rare cancer with a very poor overall prognosis. Abnormal activation of the Wnt/β-catenin as well as the IGF2 signaling plays an important role in ACC development. Studies examining rare genetic syndromes responsible for familial ACT have played an important role in identifying genetic alterations in these tumors (like TP53 or CTNNB1 mutations as well as IGF2 overexpression). Recently, genomic analyses of ACT have shown gene expression profiles associated with malignancy as well as chromosomal and methylation alterations in ACT and exome sequencing allowed to describe the mutational landscape of these tumors. This progress leads to a new classification of these tumors, opening new perspectives for the diagnosis and prognostication of ACT. This review summarizes current knowledge of adrenocortical development, growth, and tumorigenesis.

Thioredoxin Reductase 2 (TXNRD2) mutation associated with familial glucocorticoid deficiency (FGD)

CONTEXT

Classic ACTH resistance, due to disruption of ACTH signaling, accounts for the majority of cases of familial glucocorticoid deficiency (FGD). Recently FGD cases caused by mutations in the mitochondrial antioxidant, nicotinamide nucleotide transhydrogenase, have highlighted the importance of redox regulation in steroidogenesis.

OBJECTIVE

We hypothesized that other components of mitochondrial antioxidant systems would be good candidates in the etiology of FGD.

DESIGN

Whole-exome sequencing was performed on three related patients, and segregation of putative causal variants confirmed by Sanger sequencing of all family members. A TXNRD2-knockdown H295R cell line was created to investigate redox homeostasis.

SETTING

The study was conducted on patients from three pediatric centers in the United Kingdom.

PATIENTS

Seven individuals from a consanguineous Kashmiri kindred, six of whom presented with FGD between 0.1 and 10.8 years, participated in the study.

INTERVENTIONS

There were no interventions.

MAIN OUTCOME MEASURE

Identification and functional interrogation of a novel homozygous mutation segregating with the disease trait were measured.

RESULTS

A stop gain mutation, p.Y447X in TXNRD2, encoding the mitochondrial selenoprotein thioredoxin reductase 2 (TXNRD2) was identified and segregated with disease in this extended kindred. RT-PCR and Western blotting revealed complete absence of TXNRD2 in patients homozygous for the mutation. TXNRD2 deficiency leads to impaired redox homeostasis in a human adrenocortical cell line.

CONCLUSION

In contrast to the Txnrd2-knockout mouse model, in which embryonic lethality as a consequence of hematopoietic and cardiac defects is described, absence of TXNRD2 in humans leads to glucocorticoid deficiency. This is the first report of a homozygous mutation in any component of the thioredoxin antioxidant system leading to inherited disease in humans.

IMAGe syndrome: clinical and genetic implications based on investigations in three Japanese patients

OBJECTIVE

Arboleda et al. have recently shown that IMAGe (intra-uterine growth restriction, metaphyseal dysplasia, adrenal hypoplasia congenita and genital abnormalities) syndrome is caused by gain-of-function mutations of maternally expressed gene CDKN1C on chromosome 11p15.5. However, there is no other report describing clinical findings in patients with molecularly studied IMAGe syndrome. Here, we report clinical and molecular findings in Japanese patients.

PATIENTS

We studied a 46,XX patient aged 8·5 years (case 1) and two 46,XY patients aged 16·5 and 15·0 years (cases 2 and 3).

RESULTS

Clinical studies revealed not only IMAGe syndrome-compatible phenotypes in cases 1-3, but also hitherto undescribed findings including relative macrocephaly and apparently normal pituitary-gonadal endocrine function in cases 1-3, familial glucocorticoid deficiency (FGD)-like adrenal phenotype and the history of oligohydramnios in case 2, and arachnodactyly in case 3. Sequence analysis of CDKN1C, pyrosequencing-based methylation analysis of KvDMR1 and high-density oligonucleotide array comparative genome hybridization analysis for chromosome 11p15.5 were performed, showing an identical de novo and maternally inherited CDKN1C gain-of-function mutation (p.Asp274Asn) in cases 1 and 2, respectively, and no demonstrable abnormality in case 3.

CONCLUSIONS

The results of cases 1 and 2 with CDKN1C mutation would argue the following: [1] relative macrocephaly is consistent with maternal expression of CDKN1C in most tissues and biparental expression of CDKN1C in the foetal brain; [2] FGD-like phenotype can result from CDKN1C mutation; and [3] genital abnormalities may primarily be ascribed to placental dysfunction. Furthermore, lack of CDKN1C mutation in case 3 implies genetic heterogeneity in IMAGe syndrome.

Familial glucocorticoid deficiency: a diagnostic challenge during acute illness

Familial glucocorticoid deficiency (FGD) is a heterogeneous condition of isolated glucocorticoid deficiency due to adrenocorticotropic hormone (ACTH) resistance. Patients have adrenal failure with normal electrolytes. We report two Arab children with different forms of FGD, in whom the diagnosis was initially masked by their acute illness and discuss the reasons for the delay in the diagnosis of FGD in both patients. Patient 1 presented at 12 days with Serratia sepsis. She received hydrocortisone for septic shock and needed dexamethasone courses to wean her off ventilation. At 13 weeks, she had normal electrolytes, low cortisol and high ACTH in keeping with FGD. A homozygous missense mutation (T159) in MC2R confirmed the diagnosis of FGD type 1. Patient 2 was admitted at 4.5 years, with an acute exacerbation of chronic asthma. At presentation, he had hypotension, hypoglycaemia and normal electrolytes. He was given IV hydrocortisone to treat his severe asthma, and his lip hyperpigmentation was thought to be central cyanosis. Two weeks later, his lips remained dark, and cortisol was low, with markedly elevated ACTH. Family history revealed a sister aged 22 years with cerebral palsy and a healthy 15-year-old brother, who were both severely pigmented with high ACTH levels. The diagnosis of FGD type 2 was confirmed by identifying a homozygous missense mutation (p.Y59D) in MRAP in the three siblings.

CONCLUSIONS

FGD can be easily overlooked during acute illness. In a sick child, paired measurement of serum cortisol with ACTH prior to starting steroid therapy would be useful in making the diagnosis of FGD.