A novel IGSF1 mutation in a large Irish kindred highlights the need for familial screening in the IGSF1 deficiency syndrome.

OBJECTIVE: Loss-of-function mutations in IGSF1 result in X-linked central congenital hypothyroidism (CeCH), occurring in isolation or associated with additional pituitary hormone deficits. Intrafamilial penetrance is highly variable and a minority of heterozygous females are also affected. We identified and characterized a novel IGSF1 mutation and investigated its associated phenotypes in a large Irish kindred. DESIGN, PATIENTS AND MEASUREMENTS: A novel hemizygous IGSF1 mutation was identified by direct sequencing in two brothers with CeCH, and its functional consequences were characterized in vitro. Genotype-phenotype correlations were investigated in the wider kindred. RESULTS: The mutant IGSF1 protein (c.2318T > C, p.L773P) exhibited decreased plasma membrane expression in vitro due to impaired trafficking from the endoplasmic reticulum. Ten hemizygous males and 11 heterozygous females exhibited characteristic endocrine deficits. Ireland operates a TSH-based CH screening programme, which does not detect CeCH; therefore, genetic ascertainment preceded biochemical diagnosis of moderate CH in five of seven boys as well as their 75-year-old grandfather. Clinical features potentially attributable to hypothyroidism were variable; normal free T3 (FT3) and low/low normal reverse T3 (rT3) concentrations suggested that preferential deiodination of FT4 to FT3 may help maintain tissue euthyroidism in some individuals. However, neonatal jaundice, delayed speech or growth, and obesity were observed in seven subjects in whom diagnosis was delayed. CONCLUSIONS: As observed with other IGSF1 mutations, p.L773P results in variably penetrant IGSF1 deficiency syndrome. Our observations emphasize the need for multi-generation genetic ascertainment in affected families, especially where TSH-based CH screening programmes may fail to detect CeCH at birth.

Discharge outcome analysis of 1089 transgender young people referred to paediatric endocrine clinics in England 2008-2021.

INTRODUCTION: The destination of transgender and gender variant young people referred by the National Health Service (NHS) Gender Identity Development Service (GIDS) to, and discharged from the two English paediatric endocrine liaison clinics is not known. METHODS: 1151 young people referred after full assessment by the GIDS; 827 to University College London Hospital since 2008; 324 to Leeds Children's Hospital since 2013. Discharge categorisation was by agreed criteria. Eleven emigrated and 51 self-discharged. 1089 had known outcomes. RESULTS: 999/1089 (91.7%) continued identifying as gender variant. 867/999 (86.8%) were discharged to adult gender identity clinics (GICs). 166/867 (19.1%) of these were <16 years and 701/867 (80.9%) ≥16 years at initial endocrine referral. No sex differences were seen. 38/999 (3.8%) opted for non-NHS services.90/1089 ceased identifying as gender variant. In 32/1089 (2.9%), this was subsequent to their first clinic appointment.58/1089 (5.3%) stopped treatment either with the gonadotropin releasing hormone analogue (GnRHa) or gender-affirming hormones (GAH) and reverted to their birth gender: <16 years (20/217; 9.2%); ≥16 years (38/872; 4.4%).Subdividing further, 16/217 (7.4%) <16 years ceased GnRHa and 4/217 (1.8%) after GAH. Of those ≥16 years, 33/872 (3.8%) ceased GnRHa and 5/872 (0.6%) GAH. CONCLUSIONS: At discharge, 91.7% continued as transgender or gender variant, 86.8% sought ongoing care through NHS GICs. 2.9% ceased identifying as transgender after an initial consultation prior to any endocrine intervention and 5.3% stopped treatment either with GnRHa or GAH, a higher proportion in the <16 year compared with the ≥16 year groups.

Modeling HNF1B-associated monogenic diabetes using human iPSCs reveals an early stage impairment of the pancreatic developmental program.

Heterozygous mutations in HNF1B in humans result in a multisystem disorder, including pancreatic hypoplasia and diabetes mellitus. Here we used a well-controlled human induced pluripotent stem cell pancreatic differentiation model to elucidate the molecular mechanisms underlying HNF1B-associated diabetes. Our results show that lack of HNF1B blocks specification of pancreatic fate from the foregut progenitor (FP) stage, but HNF1B haploinsufficiency allows differentiation of multipotent pancreatic progenitor cells (MPCs) and insulin-secreting ß-like cells. We show that HNF1B haploinsufficiency impairs cell proliferation in FPs and MPCs. This could be attributed to impaired induction of key pancreatic developmental genes, including SOX11, ROBO2, and additional TEAD1 target genes whose function is associated with MPC self-renewal. In this work we uncover an exhaustive list of potential HNF1B gene targets during human pancreas organogenesis whose downregulation might underlie HNF1B-associated diabetes onset in humans, thus providing an important resource to understand the pathogenesis of this disease.

GATA6 Cooperates with EOMES/SMAD2/3 to Deploy the Gene Regulatory Network Governing Human Definitive Endoderm and Pancreas Formation.

Heterozygous de novo mutations in GATA6 are the most frequent cause of pancreatic agenesis in humans. In mice, however, a similar phenotype requires the biallelic loss of Gata6 and its paralog Gata4. To elaborate the human-specific requirements for GATA6, we chose to model GATA6 loss in vitro by combining both gene-edited and patient-derived pluripotent stem cells (hPSCs) and directed differentiation toward ß-like cells. We find that GATA6 heterozygous hPSCs show a modest reduction in definitive endoderm (DE) formation, while GATA6-null hPSCs fail to enter the DE lineage. Consistent with these results, genome-wide studies show that GATA6 binds and cooperates with EOMES/SMAD2/3 to regulate the expression of cardinal endoderm genes. The early deficit in DE is accompanied by a significant reduction in PDX1+ pancreatic progenitors and C-PEPTIDE+ ß-like cells. Taken together, our data position GATA6 as a gatekeeper to early human, but not murine, pancreatic ontogeny.

Persistent hyperinsulinaemic hypoglycaemia in children with Rubinstein-Taybi syndrome.

OBJECTIVE: Genetic aetiology remains unknown in up to 50% of patients with persistent hyperinsulinaemic hypoglycaemia (HH). Several syndromes are associated with HH. We report Rubinstein-Taybi syndrome (RSTS) as one of the possible causes of persistent HH. Early diagnosis and treatment of HH is crucial to prevent hypoglycaemic brain injury. DESIGN: Four RSTS patients with HH were retrospectively analysed. METHODS: Genetic investigations included next-generation sequencing-based gene panels and exome sequencing. Clinical characteristics, metabolic profile during hypoglycaemia and treatment were reviewed. RESULTS: Disease-related EP300 or CREBBP variants were found in all patients, no pathogenic variants were found in a panel of genes associated with non-syndromic HH. Two patients had classic manifestations of RSTS, three had choanal atresia or stenosis. Diagnosis of HH varied from 1 day to 18 months of age. One patient was unresponsive to treatment with diazoxide, octreotide and nifedipine, but responded to sirolimus. All required gastrostomy feeding. CONCLUSIONS: Given the rarity of RSTS (1:125 000) and HH (1:50 000), our observations indicate an association between these two conditions. We therefore recommend that clinicians should be vigilant in screening for HH in symptomatic infants with RSTS. In children with an apparent syndromic form of HH, RSTS should be considered in the differential diagnosis.

Feasibility of overnight closed-loop therapy in young children with type 1 diabetes aged 3-6†years: comparison between diluted and standard insulin strength.

OBJECTIVE: To assess feasibility of overnight closed-loop therapy in young children with type 1 diabetes and contrast closed loop using diluted versus standard insulin strength. RESEARCH DESIGN AND METHODS: Eleven children (male 6; age range 3.75-6.96 years; glycated hemoglobin 60 (14) mmol/mol; body mass index SD score 1.0 (0.8); diabetes duration 2.2 (1.0) years, mean (SD); total daily dose 12.9 (10.6, 16.5) IU/day, median (IQR)) were studied at a clinical research facility on two occasions. In random order, participants received closed loop with diluted insulin aspart (CL_Dil; 20 IU/mL) or closed loop with standard aspart (CL_Std; 100 IU/mL) from 17:00 until 8:00 the following morning. Children consumed an evening meal at 17:00 (44 (12) gCHO) and an optional bedtime snack (6 (7) gCHO) identical on both occasions. Meal insulin boluses were calculated by standard pump bolus calculators. Basal rates on insulin pump were adjusted every 15 min as directed by a model-predictive-control algorithm informed by a real-time glucose sensor values. RESULTS: Mean plasma glucose was 122 (24) mg/dL during CL_Dil vs 122 (23) mg/dL during CL_Std (p=0.993). The time spent in the target glucose range 70-145 mg/dL was 83 (70, 100)% vs 72 (54, 81)% (p=0.328). Time above 145 mg/dL was 13 (0, 27)% vs 19 (10, 45)% (p=0.477) and time spent below 70 mg/dL was 0.0 (0.0, 1.4)% vs 1.4 (0.0, 11.6)% (p=0.161). One asymptomatic hypoglycemia below 63 mg/dL occurred in one participant during CL_Dil versus six episodes in five participants during CL_Std (p=0.09). Glucose variability measured by CV of plasma glucose tended to be reduced during CL_Dil (20% (13, 31) vs 32% (24, 42), p=0.075). CONCLUSIONS: In this feasibility study, closed-loop therapy maintained good overnight glucose control with tendency towards reduced hypoglycemia and reduced glucose variability using diluted insulin. TRIAL REGISTRATION NUMBER: clinicaltrials.gov Identifier: NCT01557634.

Overnight closed-loop insulin delivery in young people with type 1 diabetes: a free-living, randomized clinical trial.

OBJECTIVE: To evaluate feasibility, safety, and efficacy of overnight closed-loop insulin delivery in free-living youth with type 1 diabetes. RESEARCH DESIGN AND METHODS: Overnight closed loop was evaluated at home by 16 pump-treated adolescents with type 1 diabetes aged 12-18 years. Over a 3-week period, overnight insulin delivery was directed by a closed-loop system, and on another 3-week period sensor-augmented therapy was applied. The order of interventions was random. The primary end point was time when adjusted sensor glucose was between 3.9 and 8.0 mmol/L from 2300 to 0700 h. RESULTS: Closed loop was constantly applied over at least 4 h on 269 nights (80%); sensor data were collected over at least 4 h on 282 control nights (84%). Closed loop increased time spent with glucose in target by a median 15% (interquartile range -9 to 43; P < 0.001). Mean overnight glucose was reduced by a mean 14 (SD 58) mg/dL (P < 0.001). Time when glucose was <70 mg/dL was low in both groups, but nights with glucose <63 mg/dL for at least 20 min were less frequent during closed loop (10 vs. 17%; P = 0.01). Despite lower total daily insulin doses by a median 2.3 (interquartile range -4.7 to 9.3) units (P = 0.009), overall 24-h glucose was reduced by a mean 9 (SD 41) mg/dL (P = 0.006) during closed loop. CONCLUSIONS: Unsupervised home use of overnight closed loop in adolescents with type 1 diabetes is safe and feasible. Glucose control was improved during the day and night with fewer episodes of nocturnal hypoglycemia.

Steroidogenic factor-1 and human disease.

Steroidogenic factor-1 (SF-1) (Ad4BP, NR5A1) is a nuclear receptor that plays a key role in adrenal and reproductive development and function. Deletion of the gene encoding Sf-1 (Nr5a1) in mice results in severe developmental defects of the adrenal gland and gonad. Consequently, initial work on the potential effects of SF-1 disruption in humans focused on individuals with primary adrenal failure, a 46,XY karyotype, complete gonadal dysgenesis, and Müllerian structures. This is a rare phenotype, but has been reported on two occasions, because of alterations that affect key DNA-binding domains of SF-1. Attention then turned to a potential wider role of SF-1 in human adrenal and reproductive disorders. Although changes in SF-1 only very rarely cause isolated adrenal failure, it is emerging that variations in SF-1 are a surprisingly frequent cause of reproductive dysfunction in humans. In 46,XY disorders of sex development, a spectrum of phenotypes has been reported including severe and partial forms of gonadal (testicular) dysgenesis, hypospadias, anorchia with microphallus, and even male factor infertility. In 46,XX females, alterations in SF-1 are associated with primary ovarian insufficiency. Thus, SF-1 seems be a more significant factor in human reproductive health than was first envisioned, with implications for adults as well as children.

Analysis of LIN28A in early human ovary development and as a candidate gene for primary ovarian insufficiency.

Lin28 proteins are emerging as important regulators of microRNAs in endocrine systems. Lin28a regulates primordial germ cell development and puberty timing in mice, whereas the related protein LIN28B is associated with age at menarche in genome-wide association studies in humans. Here, we studied expression of LIN28A and LIN28B in early human gonad development. LIN28A increased in the developing ovary between 6 and 9weeks post conception, but not in the developing testis. Immunohistochemistry demonstrated LIN28A in peripheral germ cells. LIN28B was expressed at lower levels in both tissues and did not increase with time. As disruption of Lin28a affects germ cell development in mice, LIN28A was considered a candidate gene for primary ovarian insufficiency (POI) in humans. However, no significant changes were found in 50 women studied. These findings show LIN28A is strongly expressed in germ cells during early human ovary development, but disruption of LIN28A is not a common cause of POI.

Role of DAX-1 (NR0B1) and steroidogenic factor-1 (NR5A1) in human adrenal function.

The nuclear receptor transcription factors DAX-1 (NR0B1) and SF-1 (NR5A1) regulate many aspects of adrenal and reproductive development and function. Disruption of the genes encoding these factors can be associated with pediatric adrenal disease. DAX-1 mutations are classically associated with X-linked adrenal hypoplasia congenita, hypogonadotropic hypogonadism and impaired spermatogenesis. However, other phenotypes are also being reported, such as isolated mineralocorticoid insufficiency, premature sexual development, primary adrenal insufficiency in a 46, XX patient and late-onset X-linked adrenal hypoplasia congenita and/or hypogonadotropic hypogonadism. SF-1 mutations have also been associated with primary adrenal insufficiency, together with 46, XY disorders of sex development. However it is emerging that SF-1 changes are a relatively rare cause of primary adrenal failure in humans, and most individuals with SF-1 mutations have a spectrum of 46, XY disorders of sex development phenotypes. These conditions range from 46, XY females with streak gonads and müllerian structures, through children with ambiguous genitalia and inguinal testes, to severe penoscrotal hypospadias with undescended testes. Therefore, the human gonad appears to be more sensitive than the adrenal gland to loss of SF-1 function. This review will focus on the expanding range of phenotypes associated with DAX-1 and SF-1 mutations.