Hypothesis and Theory: Evaluating the Co-Evolution of the Melanocortin-2 Receptor and the Accessory Protein MRAP1

The melanocortin receptors (MCRs) and the MRAP accessory proteins belong to distinct gene families that are unique to the chordates. During the radiation of the chordates, the melancortin-2 receptor paralog (MC2R) and the MRAP1 paralog (melanocortin-2 receptor accessory protein 1) have co-evolved to form a heterodimer interaction that can influence the ligand selectivity and trafficking properties of MC2R. This apparently spontaneous interaction may have begun with the ancestral gnathostomes and has persisted in both the cartilaginous fishes and the bony vertebrates. The ramifications of this interaction had profound effects on the hypothalamus/anterior pituitary/adrenal-interrenal axis of bony vertebrates resulting in MC2R orthologs that are exclusively selective for the anterior pituitary hormone, ACTH, and that are dependent on MRAP1 for trafficking to the plasma membrane. The functional motifs within the MRAP1 sequence and their potential contact sites with MC2R are discussed. The ramifications of the MC2R/MRAP1 interaction for cartilaginous fishes are also discussed, but currently the effects of this interaction on the hypothalamus/pituitary/interrenal axis is less clear. The cartilaginous fish MC2R orthologs have apparently retained the ability to be activated by either ACTH or MSH-sized ligands, and the effect of MRAP1 on trafficking varies by species. In this regard, the possible origin of the dichotomy between cartilaginous fish and bony vertebrate MC2R orthologs with respect to ligand selectivity and trafficking properties is discussed in light of the evolution of functional amino acid motifs within MRAP1.

Clinical course and management of pembrolizumab-associated isolated adrenocorticotrophic hormone deficiency: a new case and literature review

Hypophysitis is rarely reported in patients receiving pembrolizumab-only immunotherapies. Since the clinical presentation is usually as isolated adrenocorticotrophic hormone (ACTH) deficiency, patients may be misjudged as having clinical symptoms due to cancer or chemotherapy. A 49-year-old male with laryngeal cancer applied to our clinic just after the tenth cycle of his pembrolizumab treatment, with weakness and nausea/vomiting. Serum morning cortisol and ACTH were 0.47 mcg/dl and 10.1 pg/ml, respectively; the remaining anterior pituitary hormone levels were normal. Pituitary MRI revealed mild glandular enlargement and loss of posterior pituitary bright-spot. All symptoms and signs improved with low-dose prednisolone. This is the second reported case of pembolizumab-associated isolated ACTH deficiency having abnormal pituitary MRI findings as we have reviewed all reported cases in the literature.

Paediatric Langerhans Cell Histiocytosis Disease: Long-Term Sequelae in the Hypothalamic Endocrine System

Langerhans cell histiocytosis (LCH) is a disorder of the mononuclear phagocyte system that can affect almost any organ and system. The most common central nervous system (CNS) manifestation in LCH is the infiltration of the hypothalamic-pituitary region leading to destruction and neurodegeneration of CNS tissue. The latter causes the most frequent endocrinological manifestation, that is, central diabetes insipidus (CDI), and less often anterior pituitary hormone deficiency (APD). The reported incidence of CDI is estimated between 11.5 and 24% and is considered a risk factor for neurodegenerative disease and APD. Three risk factors for development of CDI are recognized in the majority of the studies: (1) multisystem disease, (2) the occurrence of reactivations or active disease for a prolonged period, and (3) the presence of craniofacial bone lesions. Since CDI may occur as the first manifestation of LCH, differential diagnosis of malignant diseases like germ cell tumours must be made. APD is almost always associated with CDI and can appear several years after the diagnosis of CDI. Growth hormone is the most commonly affected anterior pituitary hormone. Despite significant advances in the knowledge of LCH in recent years, little progress has been made in preventing long-term sequelae such as those affecting the hypothalamic-pituitary system.

Postpartum Cranial Diabetes Insipidus

Cranial Diabetes Insipidus is a rare diagnosis and rarer still postpartum. We present the case of 24-year-old woman who developed CDI following pregnancy. The patient had developed persistent polydipsia and polyuria 5 months following her first pregnancy. The pregnancy had been complicated by Gestational Diabetes Mellitus, Obstetric Cholestasis and a Postpartum Haemorrhage which had required a 3 unit transfusion of blood. The patient reported feeling fatigued and lightheaded and stated that she had needed to drink water frequently: around 8 litres throughout the day and 4 litres overnight. She reported that she had been unable to breastfeed but the rest of her systemic enquiry was unremarkable. The patient had attributed her symptoms of lethargy to sleepless nights with her new born baby and the polyuria as a consequence of labour and as such had presented for review at her primary care Physician 18 months following delivery. Initial investigations revealed a fasting blood glucose of 4.9 mmol/l, an Adj. Calcium of 2.23 mmol/l and a fasting urine osmolality of 85 mmol/kg. A diagnosis of DI was suspected and was confirmed by water deprivation test: the patient had an inappropriately dilute urine osmolality of 111 mmol/kg when compared to the serum osmolality of 301 mOsm/Kg at the start of the test and her urine failed to concentrate as water was withheld. Administration of DDAVP resulted in appropriate concentration of urine and therefore confirmed the diagnosis specifically as Cranial Diabetes Insipidus. Blood tests revealed normal anterior pituitary function: TSH was 2.78 mU/L, Prolactin was 361 mU/l, LH and FSH were 23.6 U/L and 5.3 U/L, IGF and GH were 197 ug/L and 0.1 ug/l and ACTH was 10 mU/L. Her basal cortisol was 392 nmol/l and was stimulated to 593 nmol/l by SST. MRI Pituitary revealed an unusually flat and broad pituitary gland with a possible tiny lesion in the posterior pituitary suggestive of an adenoma. The patient was established on DDAVP replacement therapy and her quality of life improved: she enjoyed restful sleep and reported less exhaustion. There was no anterior pituitary hormone deficiency 28 months following delivery. DI is a rare diagnosis with an estimated prevalence of 1 in 25000 people. CDI has been commonly reported as being caused by infiltrative or inflammatory pituitary disease, as an iatrogenic sequelae of pituitary surgery or as a result of a congenital defect in the production of vasopressin. We suspect that in this case the patient’s PPH may have resulted in isolated cranial diabetes insipidus though the significance of the MRI scan findings remains unclear. The learning points highlighted by this case are that CDI can occur following pregnancy in an isolated form without anterior pituitary hormone deficiency. We also highlight that patients may misattribute significant symptoms and signs of DI as being a normal part of the postpartum period resulting in a delayed diagnosis.

Hypophysitis secondary to nivolumab and pembrolizumab is a clinical entity distinct from ipilimumab-associated hypophysitis

Objective Little has been published describing hypophysitis after nivolumab or pembrolizumab treatment. We aimed to (i) assess the risk of hypophysitis following nivolumab or pembrolizumab treatment, (ii) characterize the clinical presentation and outcomes in these patients and (iii) compare these patients to hypophysitis following ipilimumab and ipilimumab plus nivolumab (combo). We hypothesized that headaches, pituitary enlargement on MRI and multiple anterior pituitary hormone deficiencies would occur less often in the nivolumab/pembrolizumab group versus ipilimumab or combo hypophysitis patients. Design and methods We conducted a multi-center retrospective review utilizing the Research Patient Database registry to evaluate individuals diagnosed with hypophysitis following treatment with nivolumab/pembrolizumab (n = 22), ipilimumab (n = 64) and combo (n = 20). Encounter notes, radiologic imaging and laboratory results for these patients were comprehensively reviewed. Results Hypophysitis was rare following treatment with nivolumab/pembrolizumab (0.5%, 17/3522) compared to ipilimumab (13.6%, 34/250), P < 0.0001. Hypophysitis was diagnosed later in nivolumab/pembrolizumab (median: 25.8 weeks, interquartile range (IR): 18.4–44.0) compared to ipilimumab (9.3, IR: 7.2–11.1) or combo patients (12.5, IR: 7.4–18.6), P < 0.0001 for both. Headache and pituitary enlargement occurred less commonly in nivolumab/pemrolizumab patients (23% and 5/18, respectively) compared to ipilimumab (75%, 60/61) and combo (75%, 16/17) treatment groups (P < 0.0001 versus ipilimumab and P = 0.001 versus combo for headache and P < 0.0001 for both for enlargement). Conclusions This study represents the first comprehensive cohort analysis of nivolumab or pembrolizumab-associated hypophysitis in a large patient group. Hypophysitis occurs rarely with these medications, and these patients have a distinct phenotype compared to hypophysitis after treatment with ipilimumab or ipilimumab plus nivolumab.

Central Diabetes Insipidus in a Patient With NFKB2 Mutation: Expanding the Endocrine Phenotype in DAVID Syndrome

Context Deficient anterior pituitary with variable immune deficiency (DAVID) syndrome is a recently described, rare disorder characterized by anterior pituitary hormone deficiencies and common variable immunodeficiency associated with NFKB2 mutations. Posterior pituitary hormone deficiencies have not been reported in patients with DAVID syndrome. Case Description We report a pediatric patient who initially presented with hypogammaglobulinemia and alopecia totalis, who was identified to have a de novo NFKB2 mutation at one year of age. He developed central diabetes insipidus and central adrenal insufficiency at three and four years of age, respectively. At seven years of age, he had not developed GH or TSH deficiencies. Whole exome sequencing ruled out known genetic causes of central diabetes insipidus, adrenal insufficiency, and hypopituitarism. Conclusion This is a report of central diabetes insipidus in a patient with DAVID syndrome caused by an NFKB2 mutation. This case report expands the evolving endocrine phenotype associated with NFKB2 mutations beyond anterior pituitary deficiencies.

Anterior hypopituitarism secondary to biopsy-proven IgG4-related hypophysitis in a young man

Summary IgG4-related disease (IgG4-RD) is an immune-mediated fibro-inflammatory condition which can affect various organs including the pituitary gland. The true annual incidence of this condition remains widely unknown. In addition, it is unclear whether IgG4 antibodies are causative or the end result of a trigger. With no specific biomarkers available, the diagnosis of IgG4-related hypophysitis remains a challenge. Additionally, there is a wide differential diagnosis. We report a case of biopsy-proven IgG4-related hypophysitis in a young man with type 2 diabetes mellitus. Learning points: IgG4-related hypophysitis is part of a spectrum of IgG4-related diseases. Clinical manifestations result from anterior pituitary hormone deficiencies with or without diabetes insipidus, which can be temporary or permanent. A combination of clinical, radiological, serological and histological evidence with careful interpretation is required to make the diagnosis. Tissue biopsy remains the gold standard investigation. Disease monitoring and long-term management of this condition is a challenge as relapses occur frequently.