Bilgin Yuksel

TAC3 and TACR3 mutations in familial hypogonadotropic hypogonadism reveal a key role for Neurokinin B in the central control of reproduction

The timely secretion of gonadal sex steroids is essential for the initiation of puberty, the postpubertal maintenance of secondary sexual characteristics and the normal perinatal development of male external genitalia. Normal gonadal steroid production requires the actions of the pituitary-derived gonadotropins, luteinizing hormone and follicle-stimulating hormone. We report four human pedigrees with severe congenital gonadotropin deficiency and pubertal failure in which all affected individuals are homozygous for loss-of-function mutations in TAC3 (encoding Neurokinin B) or its receptor TACR3 (encoding NK3R). Neurokinin B, a member of the substance P–related tachykinin family, is known to be highly expressed in hypothalamic neurons that also express kisspeptin, a recently identified regulator of gonadotropin-releasing hormone secretion. These findings implicate Neurokinin B as a critical central regulator of human gonadal function and suggest new approaches to the pharmacological control of human reproduction and sex hormone-related diseases.

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.

Thyroid hormone levels and their relationship to survival in children with bacterial sepsis and septic shock.

Objectives: Reported studies have showed alternations of thyroid hormones in critical illness mostly in adults and some in children. In this study, we aimed to measure thyroid hormone levels in children with sepsis and septic shock and investigate the relationship of these hormones with clinical state and survival. Patients and Methods: Thyroid hormone levels of children with sepsis and septic shock, and age-and sex-matched controls were measured. Results: There were 51 children in sepsis (group S), 21 children in septic shock (group SS) and 30 in the control (group C) group. Total triiodothyronine (TT 3 ) levels were (nmol/l): 0.91 ′ 0.22, 0.64 ′ 0.23, 2.11 ′ 0.59; free triiodothyronine (FT 3 ) (pmol/l): 0.027 ′ 0.006, 0.018 ′ 0.007, 0.049 ′ 0.010; total thyroxine (TT 4 ) (nmol/l): 100.62 ′ 21.93, 65.79 ′ 19.35, 109.65 ′ 19.35; free thyroxine (FT 4 ) (pmol/l): 18.06 ′ 3.87, 10.32 ′ 1.29, 19.35 ′ 3.87; and thyroid stimulating hormone (TSH) (mIU/ml): 5.0 ′ 2.0, 4.8 ′ 2.4, 5.2 ′ 3.0, in children with sepsis, septic shock, and controls, respectively. The TT 3 , FT 3 , TT 4 , and FT 4 levels of group SS were significantly lower than those of groups S and C. The TT 3 and FT 3 levels of group S were lower than in group C, but there was no significant difference between TT 4 , and FT 4 levels of groups S and C. TSH levels were slightly decreased in both sepsis and septic shock, but the difference was not significant. Eleven (21.6%) children with sepsis and 15 (71.4%) children with septic shock died (p <0.001). The levels of TT 3 , FT 3 , TT 4 and FT 4 were markedly lower in non-survivors of groups S and SS compared to survivors (p <0.001). Conclusions: These changes in the hypothalamopituitary-thyroidal axis may suggest a possible prognostic value of thyroid hormone levels in children with sepsis and septic shock. To the best of our knowledge, this report is the first study to compare thyroid hormone levels in a large number of patients with sepsis and septic shock with those in healthy controls in childhood.

Loss-of-function mutations in PNPLA6 encoding neuropathy target esterase underlie pubertal failure and neurological deficits in Gordon Holmes syndrome.

CONTEXT Gordon Holmes syndrome (GHS) is characterized by cerebellar ataxia/atrophy and normosmic hypogonadotropic hypogonadism (nHH). The underlying pathophysiology of this combined neurodegeneration and nHH remains unknown. OBJECTIVE We aimed to provide insight into the disease mechanism in GHS. METHODS We studied a cohort of 6 multiplex families with GHS through autozygosity mapping and whole-exome sequencing. RESULTS We identified 6 patients from 3 independent families carrying loss-of-function mutations in PNPLA6, which encodes neuropathy target esterase (NTE), a lysophospholipase that maintains intracellular phospholipid homeostasis by converting lysophosphatidylcholine to glycerophosphocholine. Wild-type PNPLA6, but not PNPLA6 bearing these mutations, rescued a well-established Drosophila neurodegenerative phenotype caused by the absence of sws, the fly ortholog of mammalian PNPLA6. Inhibition of NTE activity in the LβT2 gonadotrope cell line diminished LH response to GnRH by reducing GnRH-stimulated LH exocytosis, without affecting GnRH receptor signaling or LHβ synthesis. CONCLUSION These results suggest that NTE-dependent alteration of phospholipid homeostasis in GHS causes both neurodegeneration and impaired LH release from pituitary gonadotropes, leading to nHH.

Molecular Genetic Analysis of Normosmic Hypogonadotropic Hypogonadism in a Turkish Population: Identification and Detailed Functional Characterization of a Novel Mutation in the Gonadotropin-Releasing Hormone Receptor Gene

Background/Aims: Currently known mutations account for less than 15% of cases with normosmic hypogonadotropic hypogonadism (nIHH). The objective of the study was to identify novel hereditary associations in the pathogenesis of nIHH. Methods: We investigated 26 Turkish patients with nIHH (21 males and 5 females) from 22 families. The coding regions of the GnRH receptor, GnRH1, GPR54, and KISS1 genes were directly sequenced. Results: In two sisters, a novel homozygous missense mutation, R139C, located in the conserved DRS motif at the junction of the third transmembrane and the second intracellular loop of the GnRH receptor was identified. The R139C mutation almost completely abolished plasma membrane expression while having little effect on GnRH-binding affinity. The mutant receptor expression was rescued by a membrane-permeant, non-peptide GnRH receptor antagonist IN3. Conclusions: Consistent with the previous studies we were able to find mutations in only 7.6% of a well-defined group of patients with nIHH, which further suggests that yet unidentified genetic associations to explain nIHH exist.

Mutations in FEZF1 cause Kallmann syndrome.

Gonadotropin-releasing hormone (GnRH) neurons originate outside the CNS in the olfactory placode and migrate into the CNS, where they become integral components of the hypothalamic-pituitary-gonadal (HPG) axis. Disruption of this migration results in Kallmann syndrome (KS), which is characterized by anosmia and pubertal failure due to hypogonadotropic hypogonadism. Using candidate-gene screening, autozygosity mapping, and whole-exome sequencing in a cohort of 30 individuals with KS, we searched for genes newly associated with KS. We identified homozygous loss-of-function mutations in FEZF1 in two independent consanguineous families each with two affected siblings. The FEZF1 product is known to enable axons of olfactory receptor neurons (ORNs) to penetrate the CNS basal lamina in mice. Because a subset of axons in these tracks is the migratory pathway for GnRH neurons, in FEZF1 deficiency, GnRH neurons also fail to enter the brain. These results indicate that FEZF1 is required for establishment of the central component of the HPG axis in humans.

Growth hormone and insulin‐like growth factor 1 levels and their relation to survival in children with bacterial sepsis and septic shock

Objectives:  Despite improved supportive care, the mortality of sepsis and septic shock is still high. Multiple changes in the neuroendocrine systems, at least in part, are responsible for the high morbidity and mortality. A reduced circulating level of insulin‐like growth factor and an elevated level of growth hormone are the reported characteristic findings early in the course of sepsis and septic shock in adults. The aim of this study was to evaluate the changes of growth hormone/insulin‐like growth factor 1 axis in sepsis and septic shock and investigate the relationship between these hormones and survival.

Serum IL-1, IL-2, TNFα and INFγ levels of patients with type 1 diabetes mellitus and their siblings

: Type 1 diabetes mellitus (DM) develops as a result of autoimmune destruction of the pancreatic beta-cells. The aim of this study was to explore possible associations between serum levels of cytokines, IL-1, IL-2, TNFalpha and INFgamma and metabolic parameters in children with type 1 DM and their non-diabetic siblings to determine whether these cytokines could be indicators of disordered immune regulation. The study population consisted of 41 children with type 1 DM, 32 non-diabetic siblings, and 28 healthy controls. Children with DM were divided into three subgroups: 1) newly diagnosed patients with diabetic ketoacidosis (ND + DKA), 2) newly diagnosed patients without DKA (ND - DKA), and 3) previously diagnosed patients (PD). The highest serum IL-1alpha level was found in the ND - DKA group, which was significant compared to both the ND + DKA (p < 0.05) and the siblings (S) (p < 0.005). IL-2 levels were similar among all groups. The highest TNFalpha level was observed in the ND + DKA group, which was significant against the ND - DKA (p < 0.05), PD (p < 0.001), S (p < 0.05), and control (C) (p < 0.005) groups. TNFalpha concentration in the PD group was significantly lower than those of S (p< 0.005) and C (p < 0.001) groups. The ND - DKA group had the highest INFgamma and this was statistically significant when compared with the S (p < 0.005) and C (p < 0.05) groups. Both the newly diabetics and all diabetics as a group had statistically significantly higher INFgamma levels than both the S (p < 0.01 for both) and C (p < 0.05 for both) groups. In the diabetics as a whole group, TNFalpha showed correlations with INFgamma (r = 0.370, p < 0.05). IL-1 showed correlation with TNFalpha (r = 0.368, p < 0.05) INFgamma (r = 0.796, p < 0.001) and IL-2 (r = 0.862, p < 0.001) in the all diabetics group. IL-2 was correlated with TNFalpha (r = 0.320, p < 0.05) and INFgamma (r = 0.754, p < 0.01) in the all diabetics group. In conclusion, our results suggest that proinflammatory cytokines TNFalpha, INFgamma, IL-1alpha and IL-2 may play important roles alone or in combination in the pathogenesis of type 1 diabetes mellitus.

Wolcott-Rallison syndrome due to the same mutation (W522X) in EIF2AK3 in two unrelated families and review of the literature.

Ozbek MN, Senée V, Aydemir S, Kotan LD, Mungan NO, Yuksel B, Julier C, Topaloglu AK. Wolcott–Rallison syndrome due to the same mutation (W522X) in EIF2AK3 in two unrelated families and review of the literature.

Pulmonary hypertension, heart failure and neutropenia due to diazoxide therapy

Primary persistent hyperinsulinaemic hypoglycaemia is characterised by clinical symptoms that occur when blood glucose levels drop below the normal range. Diazoxide treatment remains the mainstay of medical therapy. Tolerance of diazoxide is usually excellent, but several side effects of this drug have been described. We present a 4-month-old girl who developed pulmonary hypertension, heart failure and neutropenia during diazoxide therapy. Diazoxide toxicity was suspected and the drug was withdrawn on day 13. During the next 3 days, respiratory and haemodynamic status dramatically improved and she was weaned from mechanical ventilation. Control white blood cell count was 8800 cells/mm3 and a new echocardiography showed modreduction of pulmonary artificial pressure to 20 mmHg and resolution of atrial and ventricular enlargement. Paediatric physicians should be in mind of pulmonary hypertension, heart failure and neutropenia developing during diazoxide therapy.