Isolated congenital ACTH deficiency: a cleavage enzyme defect?

Idiopathic Isolated Adrenocorticotropic Hormone Deficiency: A Single-Center Retrospective Study

Idiopathic isolated adrenocorticotrophic hormone deficiency (IIAD) is rare, with high clinical omission and misdiagnosis rates. This study retrospectively collected information on clinical presentation, laboratory findings, and treatment response of 17 patients with IIAD at Jining No. 1 People's Hospital from January 2014 to December 2022. The clinical characteristics were summarized, and the pertinent data were analyzed. As a result, most of the patients with IIAD were male (94.12%), with age at onset ranging from 13 to 80 years. The primary manifestations were anorexia (88.24%), nausea (70.59%), vomiting (47.06%), fatigue (64.71%), and neurological or psychiatric symptoms (88.24%). The median time to diagnosis was 2 months and the longest was 10 years. Laboratory tests mostly showed hyponatremia (88.24%) and hypoglycemia (70.59%). The symptoms and laboratory indicators returned to normal after supplementing patients with glucocorticoids. IIAD has an insidious onset and atypical symptoms; it was often misdiagnosed as gastrointestinal, neurological, or psychiatric disease. The aim of this study was to improve clinicians' understanding of IIAD, patients with unexplained gastrointestinal symptoms, neurological and psychiatric symptoms, hyponatremia, or hypoglycemia should be evaluated for IIAD and ensure early diagnosis and treatment.

Presence of aberrant adrenocorticotropic hormone precursors in two cases of McCune-Albright syndrome

McCune-Albright syndrome (MAS) is a rare disorder. MAS is classically defined by the occurrence of fibrous dysplasia, café-au-lait skin macules, and precocious puberty. In addition to precocious puberty, other hyperfunctioning endocrinopathies may occur. We evaluated hypothalamic-pituitary-adrenal function in two cases of typical MAS associated with fibrous dysplasia and growth hormone excess. Pituitary adenoma or hyperplasia was not detected by magnetic resonance imaging. Hormonal data showed normal or low cortisol levels, despite high ACTH levels in the blood. A high ratio of circulating ACTH to cortisol was found in the two cases. Insulin tolerance and CRH tests showed hyper-responses of ACTH and an insufficient increase in cortisol levels. No involvement of 11β-HSD1 by GH excess was suggested because basal levels of ACTH and cortisol showed no changes, even after therapy for acromegaly by somatostatin analogues. Patients with Cushing's disease cases of pituitary macroadenoma can have high circulating ACTH precursor levels, and elevated ACTH precursors have been observed in ectopic ACTH syndrome. Autonomous cortisol excess was excluded by the level of midnight cortisol and the level of cortisol after a low-dose dexamethasone suppression test in the two cases. Finally, the gel filtration profiles of immunoreactive ACTH contents showed the presence of aberrant ACTH precursors. To the best of our knowledge, there have been no reports of MAS associated with aberrant ACTH precursors. Our findings in these cases emphasize that attention should be to secretion of inactive ACTH precursors in MAS.

Neuroendocrinological and Epigenetic Mechanisms Subserving Autonomic Imbalance and HPA Dysfunction in the Metabolic Syndrome

Impact of environmental stress upon pathophysiology of the metabolic syndrome (MetS) has been substantiated by epidemiological, psychophysiological, and endocrinological studies. This review discusses recent advances in the understanding of causative roles of nutritional factors, sympathomedullo-adrenal (SMA) and hypothalamic-pituitary adrenocortical (HPA) axes, and adipose tissue chronic low-grade inflammation processes in MetS. Disturbances in the neuroendocrine systems for leptin, melanocortin, and neuropeptide Y (NPY)/agouti-related protein systems have been found resulting directly in MetS-like conditions. The review identifies candidate risk genes from factors shown critical for the functioning of each of these neuroendocrine signaling cascades. In its meta-analytic part, recent studies in epigenetic modification (histone methylation, acetylation, phosphorylation, ubiquitination) and posttranscriptional gene regulation by microRNAs are evaluated. Several studies suggest modification mechanisms of early life stress (ELS) and diet-induced obesity (DIO) programming in the hypothalamic regions with populations of POMC-expressing neurons. Epigenetic modifications were found in cortisol (here HSD11B1 expression), melanocortin, leptin, NPY, and adiponectin genes. With respect to adiposity genes, epigenetic modifications were documented for fat mass gene cluster APOA1/C3/A4/A5, and the lipolysis gene LIPE. With regard to inflammatory, immune and subcellular metabolism, PPARG, NKBF1, TNFA, TCF7C2, and those genes expressing cytochrome P450 family enzymes involved in steroidogenesis and in hepatic lipoproteins were documented for epigenetic modifications.

Congenital early onset isolated adrenocorticotropin deficiency associated with a TPIT gene mutation

TPIT is a highly cell-restricted transcription factor that is required for the expression of the propiomelanocortin (POMC) gene and for terminal differentiation of the pituitary corticotroph lineage. Its exclusive expression in pituitary POMC-expressing cells has suggested that its mutation may cause isolated deficiency of pituitary ACTH. We present a neonate with the diagnosis of congenital early onset isolated ACTH deficiency (IAD) associated with a loss of POMC function as a result of a missense mutation in the TPIT gene. A 5 day-old male infant was admitted for hypoglycemia, limpness and conjugated hyperbilirubinemia. Laboratory investigations indicated low plasma cortisol concentration (0.1 microg/dl) accompanying a very low ACTH (<5 pg/ml) concentration. An increase in plasma cortisol concentration following stimulation with low dose exogenous ACTH was observed. On replacement therapy with hydrocortisone (15 mg/m2/day orally), cholestatic jaundice and hypoglycemia resolved and subsequent normal growth (weight, height and head circumference, 25th, 10th and 50th percentile, respectively) and development was achieved without recurrence of hypoglycemic episodes.

Controle neuroendócrino do peso corporal: implicações na gênese da obesidade

O peso corporal é regulado por uma interação complexa entre hormônios e neuropeptídeos, sob o controle principal de núcleos hipotalâmicos. Mutações nos genes de hormônios e neuropeptídeos, de seus receptores ou de elementos regulatórios, têm sido descritas na espécie humana, mas são tidas como raras, não explicando as formas mais comuns de obesidade. No entanto, o estudo destas mutações tem propiciado um grande avanço nos conhecimentos sobre a base genética e a fisiopatologia da obesidade, possibilitando o estudo e abrindo perspectivas para o desenvolvimento de novas modalidades terapêuticas. Recentemente, demonstrou-se que mutações no receptor 4 da melanocortina podiam ser encontradas em até 5% dos casos de obesidade severa, representando até o presente momento a forma mais prevalente de obesidade monogênica na espécie humana. Nesta revisão, são discutidas as diversas mutações descritas nos seres humanos de elementos da rede neuroendócrina de controle do peso corporal, bem como as implicações dos mesmos na gênese da obesidade.

Mutations in the human proopiomelanocortin gene

The melanocortin peptides and their receptors represent one of the most complex systems in human endocrinology. Hormonal regulation includes pigmentation, weight maintenance, adrenal function, and exocrine gland secretion via endocrine, paracrine, autocrine, and neurocrine action of melanocortin peptides at five different but homologous melanocortin receptors. Genetic relevance of the melanocortin system for human physiology was initially shown by mutations in the different melanocortin receptor genes, first described in the melanocortin-2 receptor gene in 1993 as one reason for congenital hypocortisolism. Because all ligands within the melanocortin systems are derived from one single precursor hormone, proopiomelanocortin (POMC), a genetic defect in the POMC gene could have been expected to affect all functional components of the melanocortin system. Accordingly, patients with a complete defect of the POMC gene product due to homozygous or compound heterozygous loss of function mutations were shown to be affected mainly by red hair, early-onset obesity, and congenital hypocortisolism. No further obvious clinical problems were described in these patients, suggesting that no additional function of the melanocortin system has escaped recognition. However, whether partial loss of function mutations in the POMC gene might lead to more circumscribed phenotypes, especially common obesity, remains an open question.

Adrenal insufficiency

Adrenal insufficiency is caused by either primary adrenal failure (mostly due to autoimmune adrenalitis) or by hypothalamic-pituitary impairment of the corticotropic axis (predominantly due to pituitary disease). It is a rare disease, but is life threatening when overlooked. Main presenting symptoms such as fatigue, anorexia, and weight loss are non-specific, thus diagnosis is often delayed. The diagnostic work-up is well established but some pitfalls remain, particularly in the identification of secondary adrenal insufficiency. Despite optimised life-saving glucocorticoid-replacement and mineralocorticoid-replacement therapy, health-related quality of life in adrenal insufficiency is more severely impaired than previously thought. Dehydroepiandrosterone-replacement therapy has been introduced that could help to restore quality of life. Monitoring of glucocorticoid-replacement quality is hampered by lack of objective methods of assessment, and is therefore largely based on clinical grounds. Thus, long-term management of patients with adrenal insufficiency remains a challenge, requiring an experienced specialist. However, all doctors should know how to diagnose and manage suspected acute adrenal failure.

Differentiation and regulation of the corticotropic pituitary cell

A number of primary diseases of the pituitary with adrenocorticotropin dysregulation have been recognized. A few genetic defects have been identified as causes of secondary adrenocortical insufficiency. Much less is known about the ontogeny of corticotrophic tumours leading to a hypercorticolaemic state. To improve the diagnosis and treatment of these disorders, a better understanding of the mechanisms of corticotrophic pituitary cell differentiation and regulation is of clear interest. Studies using molecular tools have enhanced our knowledge over recent years, and a few reports of considerable relevance are summarized in this review.

Implications of proopiomelanocortin (POMC) mutations in humans: the POMC deficiency syndrome

The recent discovery of the contribution of proopiomelanocortin (POMC)-derived peptides to the regulation of energy homeostasis and exocrine gland secretion in mice aroused new interest in the complex function of the endocrine POMC network. In addition, the first mutations in the gene encoding POMC have been identified in two patients affected by adrenal insufficiency, early onset severe obesity and red hair pigmentation. Therefore, the focus of this brief review will be the detailed discussion of the implications of these new findings in the physiology of the human POMC ligand-receptor system.

Prohormones: their clinical relevance

The majority of peptide hormones and neuropeptides are synthesized as precursors, which are cleaved in a sequence-specific and tissue-specific manner to yield the biologically active peptides. There has been considerable progress in the past ten years in understanding the nature and mechanism of action of the prohormone convertases that cleave these prohormones. Evidence from knockout technology and clinical examples of gene mutations has provided functional information on disruption of prohormone cleavage and the bioactivity of prohormones. There are specific examples of the clinical relevance of circulating prohormones, such as adrenocorticotrophin (ACTH) precursors and proinsulin. The central issues that still remain are: (1) What is the relative importance of each of the different processing pathways and processing enzymes in regulating hormone action? (2) How do the serum concentrations of prohormones compare with the mature hormone levels? (3) What are the biological consequences of prohormones in the circulation?

Severe early-onset obesity, adrenal insufficiency and red hair pigmentation caused by POMC mutations in humans

Sequential cleavage of the precursor protein pre-pro-opiomelanocortin (POMC) generates the melanocortin peptides adrenocorticotrophin (ACTH), melanocyte-stimulating hormones (MSH) alpha, beta and gamma as well as the opioid-receptor ligand beta-endorphin. While a few cases of isolated ACTH deficiency have been reported (OMIM 201400), an inherited POMC defect has not been described so far. Recent studies in animal models elucidated a central role of alpha-MSH in the regulation of food intake by activation of the brain melanocortin-4-receptor (MC4-R; refs 3-5) and the linkage of human obesity to chromosome 2 in close proximity to the POMC locus, led to the proposal of an association of POMC with human obesity. The dual role of alpha-MSH in regulating food intake and influencing hair pigmentation predicts that the phenotype associated with a defect in POMC function would include obesity, alteration in pigmentation and ACTH deficiency. The observation of these symptoms in two probands prompted us to search for mutations within their POMC genes. Patient 1 was found to be a compound heterozygote for two mutations in exon 3 (G7013T, C7133delta) which interfere with appropriate synthesis of ACTH and alpha-MSH. Patient 2 was homozygous for a mutation in exon 2 (C3804A) which abolishes POMC translation. These findings represent the first examples of a genetic defect within the POMC gene and define a new monogenic endocrine disorder resulting in early-onset obesity, adrenal insufficiency and red hair pigmentation.

Linkage of congenital isolated adrenocorticotropic hormone deficiency to the corticotropin releasing hormone locus using simple sequence repeat polymorphisms

Genetic screening techniques using simple sequence repeat polymorphisms were applied to investigate the molecular nature of congenital isolated adrenocorticotropic hormone (ACTH) deficiency. We hypothesize that this rare cause of hypocortisolism shared by a brother and sister with two unaffected sibs and unaffected parents is inherited as an autosomal recessive single gene mutation. Genes involved in the hypothalamic-pituitary axis controlling cortisol sufficiency were investigated for a causal role in this disorder. Southern blotting showed no detectable mutations of the gene encoding pro-opiomelanocortin (POMC), the ACTH precursor. Other candidate genes subsequently considered were those encoding neuroendocrine convertase-1, and neuroendocrine convertase-2 (NEC-1, NEC-2), and corticotropin releasing hormone (CRH). Tests for linkage were performed using polymorphic di- and tetranucleotide simple sequence repeat markers flanking the reported map locations for POMC, NEC-1, NEC-2, and CRH. The chromosomal haplotypes determined by the markers flanking the loci for POMC, NEC-1, and NEC-2 were not compatible with linkage. However, 22 individual markers defining the chromosomal haplotypes flanking CRH were compatible with linkage of the disorder to the immediate area of this gene on chromosome 8. Based on these data, we hypothesize that the ACTH deficiency in this family is due to an abnormality of CRH gene structure or expression. These results illustrate the useful application of high density genetic maps constructed with simple sequence repeat markers for inclusion/exclusion studies of candidate genes in even very small nuclear families segregating for unusual phenotypes.

The molecular pathology of pituitary hormone deficiency and resistance

In this chapter, we have reviewed the fast-moving area of the molecular pathology of pituitary hormone deficiencies and resistance. Examples have been described affecting all levels of pituitary function, i.e. the releasing hormone, its receptor, the pituitary hormone and its receptor, and the development of the pituitary gland. Other examples in these genes, and in those in which no mutation has yet been found, will undoubtedly be discovered in the next few years, throwing light on the structural basis of the gene product's function and allowing a greater understanding of endocrine physiology and pathophysiology. The main reason for this rapid progress in knowledge is the recent technological advances in mutation detection, which bring this activity within the grasp of the majority of reasonably equipped laboratories. Technological advancement, however is not all that it takes to carry out this work. The conditions caused by genetic damage such as we have described are rare, and there is clearly a requirement for great awareness on the part of the clinical endocrinologist. Patients in whom it is suspected that mutations such as these may occur require careful clinical and biochemical work-up. Indeed, in many instances, careful thought has to go into deciding what the phenotype of a particular mutation might be. Thus, the requirement for close collaboration between clinical and molecular endocrinologists has to be the important message for the future in this area of research.