POU6F2 mutation in humans with pubertal failure alters GnRH transcript expression.

Idiopathic hypogonadotropic hypogonadism (IHH) is characterized by the absence of pubertal development and subsequent impaired fertility often due to gonadotropin-releasing hormone (GnRH) deficits. Exome sequencing of two independent cohorts of IHH patients identified 12 rare missense variants in POU6F2 in 15 patients. POU6F2 encodes two distinct isoforms. In the adult mouse, expression of both isoform1 and isoform2 was detected in the brain, pituitary, and gonads. However, only isoform1 was detected in mouse primary GnRH cells and three immortalized GnRH cell lines, two mouse and one human. To date, the function of isoform2 has been verified as a transcription factor, while the function of isoform1 has been unknown. In the present report, bioinformatics and cell assays on a human-derived GnRH cell line reveal a novel function for isoform1, demonstrating it can act as a transcriptional regulator, decreasing GNRH1 expression. In addition, the impact of the two most prevalent POU6F2 variants, identified in five IHH patients, that were located at/or close to the DNA-binding domain was examined. Notably, one of these mutations prevented the repression of GnRH transcripts by isoform1. Normally, GnRH transcription increases as GnRH cells mature as they near migrate into the brain. Augmentation earlier during development can disrupt normal GnRH cell migration, consistent with some POU6F2 variants contributing to the IHH pathogenesis.

Genetic testing can change diagnosis and treatment in children with congenital hypothyroidism.

Objective: Guidelines on congenital hypothyroidism (CH) recommend that genetic testing should aim to improve diagnosis, treatment or prognosis, but it is unclear which patients would benefit most from the genetic investigation. We aimed to investigate the genetic etiology of transient CH (TCH) and permanent CH (PCH) in a well-characterized cohort, and thereby evaluate the impact of genetic testing on the management and prognosis of children with CH. Methods: A total of 48 CH patients with normal, goitrous (n 5) or hypoplastic thyroid (n 5) were studied by high-throughput sequencing using a custom-designed 23-gene panel. Patients initially categorized as TCH (n 15), PCH (n 26) and persistent hyperthyrotropinemia (PHT, n 7) were re-evaluated after genetic testing. Results: Re-evaluation based on genetic testing changed the initial diagnoses from PCH to PHT (n 2) or TCH (n 3) and from PHT to TCH (n 5), which resulted in a final distribution of TCH (n 23), PCH (n 21) and PHT (n 4). Genetic analysis also allowed us to discontinue treatment in five patients with monoallelic TSHR or DUOX2, or no pathogenic variants. The main reasons for changes in diagnosis and treatment were the detection of monoallelic TSHR variants and the misdiagnosis of thyroid hypoplasia on neonatal ultrasound in low birthweight infants. A total of 41 (35 different, 15 novel) variants were detected in 65% (n 31) of the cohort. These variants, which most frequently affected TG, TSHR and DUOX2, explained the genetic etiology in 46% (n 22) of the patients. The molecular diagnosis rate was significantly higher in patients with PCH (57%, n 12) than TCH (26%, n 6). Conclusions: Genetic testing can change diagnosis and treatment decisions in a small proportion of children with CH, but the resulting benefit may outweigh the burden of lifelong follow-up and treatment.

Nephrogenic Syndrome of Inappropriate Antidiuresis Mimicking Hyporeninemic Hypoaldosteronism: Case Report of Two Infants

Nephrogenic syndrome of inappropriate antidiuresis (NSIAD) is an X-linked disease caused by activating mutations in the arginine vasopressin (AVP) receptor-2 (AVPR2) gene. Affected patients excrete concentrated urine despite very low levels of AVP, and consequently develop euvolemic hyponatremia. Due to its low frequency, patients may be misdiagnosed and treated incorrectly. We report two related male infants with NSIAD that was initially confused with hyporeninemic hypoaldosteronism (HH). First, a 2-month-old male presented with hyponatremia, low plasma osmolality, relatively high urine osmolality, and low plasma renin-aldosterone levels. These clinical and laboratory findings were compatible with syndrome of inappropriate antidiuretic hormone (ADH) secretion without apparent cause. Consequently, fludrocortisone was initiated with a presumptive diagnosis of HH. While correcting hyponatremia, fludrocortisone treatment led to hypertension and was discontinued promptly. The second patient, aged one year, was admitted with a history of oligohydramnios, had been hospitalized four times due to hyponatremia since birth, and had a diagnosis of epilepsy. Similarly, the second infant had clinical and laboratory findings compatible with syndrome of inappropriate ADH secretion with no apparent cause. Fluid restriction normalized his serum sodium despite the plasma AVP level being undetectable. In both infants, AVPR2 gene analysis revealed a known mutation (c.409C>T; p.R137C) and confirmed the diagnosis of NSIAD. In conclusion, NSIAD should be considered in all patients with unexplained euvolemic hyponatremia despite high urine osmolality. If NSAID is not considered, the plasma reninaldosterone profile can be confused with HH, especially in infants.

Inactivating NHLH2 variants cause idiopathic hypogonadotropic hypogonadism and obesity in humans.

Metabolism has a role in determining the time of pubertal development and fertility. Nonetheless, molecular/cellular pathways linking metabolism/body weight to puberty/reproduction are unknown. The KNDy (Kisspeptin/Neurokinin B/Dynorphin) neurons in the arcuate nucleus of the hypothalamus constitute the GnRH (gonadotropin-releasing hormone) pulse generator. We previously created a mouse model with a whole-body targeted deletion of nescient helix-loop-helix 2 (Nhlh2; N2KO), a class II member of the basic helix-loop-helix family of transcription factors. As this mouse model features pubertal failure and late-onset obesity, we wanted to study whether NHLH2 represents a candidate molecule to link metabolism and puberty in the hypothalamus. Exome sequencing of a large Idiopathic Hypogonadotropic Hypogonadism cohort revealed obese patients with rare sequence variants in NHLH2, which were characterized by in-silico protein analysis, chromatin immunoprecipitation, and luciferase reporter assays. In vitro heterologous expression studies demonstrated that the variant p.R79C impairs Nhlh2 binding to the Mc4r promoter. Furthermore, p.R79C and other variants show impaired transactivation of the human KISS1 promoter. These are the first inactivating human variants that support NHLH2's critical role in human puberty and body weight control. Failure to carry out this function results in the absence of pubertal development and late-onset obesity in humans.

Catch-up Growth and Discontinuation of Fludrocortisone Treatment in Aldosterone Synthase Deficiency.

BACKGROUND: Aldosterone synthase deficiency (ASD) caused by mutations in the CYP11B2 gene is characterized by isolated mineralocorticoid deficiency. Data are scarce regarding clinical and biochemical outcomes of the disease in the follow-up. OBJECTIVE: Assessment of the growth and steroid profiles of patients with ASD at the time of diagnosis and after discontinuation of treatment. DESIGN AND METHOD: Children with clinical diagnosis of ASD were included in a multicenter study. Growth and treatment characteristics were recorded. Plasma adrenal steroids were measured using liquid chromatography-mass spectrometry. Genetic diagnosis was confirmed by CYP11B2 gene sequencing and in silico analyses. RESULTS: Sixteen patients from 12 families were included (8 females; median age at presentation: 3.1 months, range: 0.4 to 8.1). The most common symptom was poor weight gain (56.3%). Median age of onset of fludrocortisone treatment was 3.6 months (range: 0.9 to 8.3). Catch-up growth was achieved at median 2 months (range: 0.5 to 14.5) after treatment. Fludrocortisone could be stopped in 5 patients at a median age of 6.0 years (range: 2.2 to 7.6). Plasma steroid profiles revealed reduced aldosterone synthase activity both at diagnosis and after discontinuation of treatment compared to age-matched controls. We identified 6 novel (p.Y195H, c.1200 + 1G > A, p.F130L, p.E198del, c.1122-18G > A, p.I339_E343del) and 4 previously described CYP11B2 variants. The most common variant (40%) was p.T185I. CONCLUSIONS: Fludrocortisone treatment is associated with a rapid catch-up growth and control of electrolyte imbalances in ASD. Decreased mineralocorticoid requirement over time can be explained by the development of physiological adaptation mechanisms rather than improved aldosterone synthase activity. As complete biochemical remission cannot be achieved, a long-term surveillance of these patients is required.

Evaluation of children with type 1 diabetes mellitus in terms of overweight/obesity in tertiary care hospital.

OBJECTIVES: Obesity is a growing problem in type 1 diabetes mellitus (T1DM) today. The aim of our study is to determine the frequency of overweight/obesity at the time of diagnosis and during follow-up in children with T1DM as well as review the conditions that may accompany. METHODS: A total of 315 patients with T1DM were retrospectively analyzed. The patients were divided into two groups as normal weight and overweight/obese. The two groups were compared in terms of age at diagnosis, birth weight, anthropometric measurements, insulin dose used and blood pressure measurements, and insulin, c-peptide, hemoglobin A1c, triglyceride, and high-density lipoprotein levels at the time of diagnosis and follow-up. RESULTS: The height, weight and body mass index standard deviation (BMI SD) scores, and c-peptide levels at the time of diagnosis of the overweight/obese group were higher than those with normal weight (p<0.001 and p = 0.008, respectively). The frequency of dyslipidemia and hypertension was higher in the overweight/obese group than in the normal weight group [18.2 vs. 5% (p = 0.015) and 10 vs. 1.5% (p = 0.003), respectively]. CONCLUSIONS: In our study, the fact that the overweight/obese group had higher BMI and c-peptide and lower HDL values at the time of diagnosis can be evaluated as indicators that insulin resistance syndrome can accompany T1DM from the beginning (double diabetes). When determining the treatment and follow-up strategies of patients with T1DM, considering the risk of obesity and taking the necessary precautions is very important in terms of morbidity.