Genetics of congenital central hypogonadism

Diagnosing and treating anterior pituitary hormone deficiency in pediatric patients

Hypopituitarism, or the failure to secrete hormones produced by the anterior pituitary (adenohypophysis) and/or to release hormones from the posterior pituitary (neurohypophysis), can be congenital or acquired. When more than one pituitary hormone axis is impaired, the condition is known as combined pituitary hormone deficiency (CPHD). The deficiency may be primarily due to a hypothalamic or to a pituitary disorder, or concomitantly both, and has a negative impact on target organ function. This review focuses on the pathophysiology, diagnosis and management of anterior pituitary hormone deficiency in the pediatric age. Congenital hypopituitarism is generally due to genetic disorders and requires early medical attention. Exposure to toxicants or intrauterine infections should also be considered as potential etiologies. The molecular mechanisms underlying the fetal development of the hypothalamus and the pituitary are well characterized, and variants in the genes involved therein may explain the pathophysiology of congenital hypopituitarism: mutations in the genes expressed in the earliest stages are usually associated with syndromic forms whereas variants in genes involved in later stages of pituitary development result in non-syndromic forms with more specific hormone deficiencies. Tumors or lesions of the (peri)sellar region, cranial radiation therapy, traumatic brain injury and, more rarely, other inflammatory or infectious lesions represent the etiologies of acquired hypopituitarism. Hormone replacement is the general strategy, with critical periods of postnatal life requiring specific attention.

Case report: Novel SIN3A loss-of-function variant as causative for hypogonadotropic hypogonadism in Witteveen-Kolk syndrome

Pubertal delay can be due to hypogonadotropic hypogonadism (HH), which may occur in association with anosmia or hyposmia and is known as Kallmann syndrome (OMIM #308700). Recently, hypogonadotropic hypogonadism has been suggested to overlap with Witteveen-Kolk syndrome (WITKOS, OMIM #613406) associated with 15q24 microdeletions encompassing SIN3A. Whether hypogonadotropic hypogonadism is due to haploinsufficiency of SIN3A or any of the other eight genes present in 15q24 is not known. We report the case of a female patient with delayed puberty associated with intellectual disability, behavior problems, dysmorphic facial features, and short stature, at the age of 14 years. Clinical, laboratory, and imaging assessments confirmed the diagnosis of Kallmann syndrome. Whole-exome sequencing identified a novel heterozygous frameshift variant, NM_001145358.2:c.3045_3046dup, NP_001138830.1:p.(Ile1016Argfs*6) in SIN3A, classified as pathogenic according to the American College of Medical Genetics and Genomics (ACMG/AMP) criteria. Reverse phenotyping led to the clinical diagnosis of WITKOS. No other variant was found in the 96 genes potentially related to hypogonadotropic hypogonadism. The analysis of the other contiguous seven genes to SIN3A in 15q24 did not reveal any clinically relevant variant. In conclusion, these findings point to SIN3A as the gene in 15q24 related to the reproductive phenotype in patients with overlapping WITKOS and Kallmann syndrome.

Primary cilia as dynamic and diverse signalling hubs in development and disease

Primary cilia, antenna-like sensory organelles protruding from the surface of most vertebrate cell types, are essential for regulating signalling pathways during development and adult homeostasis. Mutations in genes affecting cilia cause an overlapping spectrum of >30 human diseases and syndromes, the ciliopathies. Given the immense structural and functional diversity of the mammalian cilia repertoire, there is a growing disconnect between patient genotype and associated phenotypes, with variable severity and expressivity characteristic of the ciliopathies as a group. Recent technological developments are rapidly advancing our understanding of the complex mechanisms that control biogenesis and function of primary cilia across a range of cell types and are starting to tackle this diversity. Here, we examine the structural and functional diversity of primary cilia, their dynamic regulation in different cellular and developmental contexts and their disruption in disease.

Testosterone Replacement Therapy in the Aged Male: Monitoring Patients’ Quality of Life Utilizing Scoring Systems

Hypogonadism has been associated with significant deterioration of well-being. In the aging male, late-onset hypogonadism affects sexual life, mental health, levels of energy, lower urinary tract symptoms and, therefore, quality of life may be found significantly deteriorated. Testosterone replacement or supplementation therapy has been found efficient to reverse the adverse effects of hypogonadism and improve quality of life. Scales and questionnaires assessing the general health, urinary symptoms, sexual health, and cognition can provide a thorough assessment of the clinical syndrome, optimize treatment, assist the follow-up, and facilitate referrals to other specialties depending on the chief complaint. A systematic assessment might combine several tools, but the optimal ones and the exact usage is unknown. In this narrative review, we are flipping through the literature presenting the available tools per domain for the assessment of quality of life in men on testosterone replacement therapy and we discuss the optimal usage.

A Novel FGFR1 Missense Mutation in a Portuguese Family with Congenital Hypogonadotropic Hypogonadism

Congenital hypogonadotropic hypogonadism (CHH) is a rare reproductive endocrine disorder characterized by complete or partial failure of pubertal development and infertility due to deficiency of the gonadotropin-releasing hormone (GnRH). CHH has a significant clinical heterogeneity and can be caused by mutations in over 30 genes. The aim of this study was to investigate the genetic defect in two siblings with CHH. A woman with CHH associated with anosmia and her brother with normosmic CHH were investigated by whole exome sequencing. The genetic studies revealed a novel heterozygous missense mutation in the Fibroblast Growth Factor Receptor 1 (FGFR1) gene (NM_023110.3: c.242T>C, p.Ile81Thr) in the affected siblings and in their unaffected father. The mutation affected a conserved amino acid within the first Ig-like domain (D1) of the protein, was predicted to be pathogenic by structure and sequence-based prediction methods, and was absent in ethnically matched controls. These were consistent with a critical role for the identified missense mutation in the activity of the FGFR1 protein. In conclusion, our identification of a novel missense mutation of the FGFR1 gene associated with a variable expression and incomplete penetrance of CHH extends the known mutational spectrum of this gene and may contribute to the understanding of the pathogenesis of CHH.