Short stature related to Growth Hormone Insensitivity (GHI) in childhood

Monogenic causes of familial short stature

Genetic factors play a crucial role in determining human height. Short stature commonly affects multiple family members and therefore, familial short stature (FSS) represents a significant proportion of growth disorders. Traditionally, FSS was considered a benign polygenic condition representing a subcategory of idiopathic short stature (ISS). However, advancements in genetic research have revealed that FSS can also be monogenic, inherited in an autosomal dominant manner and can result from different mechanisms including primary growth plate disorders, growth hormone deficiency/insensitivity or by the disruption of fundamental intracellular pathways. These discoveries have highlighted a broader phenotypic spectrum for monogenic forms of short stature, which may exhibit mild manifestations indistinguishable from ISS. Given the overlapping features and the difficulty in differentiating polygenic from monogenic FSS without genetic testing, some researchers redefine FSS as a descriptive term that encompasses any familial occurrence of short stature, regardless of the underlying cause. This shift emphasizes the complexity of diagnosing and managing short stature within families, reflecting the diverse genetic landscape that influences human growth.

The clinical and genetic aspects of six individuals with GH1 variants and isolated growth hormone deficiency type II

Background

Isolated growth hormone deficiency type II (IGHD II) is an autosomal dominant disorder characterized by a GH1 gene variant resulting in a significant reduction in growth hormone (GH) secretion and a subsequent decrease of plasma insulin-like growth factor 1 (IGF-1) levels and eventual growth impairment.

Objective

This study aimed to identify causative variants in six Chinese families with IGHD II, exploring both clinical and genetic characteristics.

Methods

Detailed clinical data, including clinical presentations, physical charateristics, medical and family histories, as well as genetic test results, were systematically examined.

Results

Six children, comprising four males and two females, with a mean age of 4.64 ± 1.15 years, exhibited short stature with a mean height of -3.95 ± 1.41 SDS. Four of them had a family history of short stature, while one patient presented with pulmonary hypertension. All children demonstrated GH deficiency in growth hormone stimulation tests (mean peak GH value: 2.83 ± 2.46 ng/mL). Exome sequencing for the six patients and targeted gene sequencing for their family members revealed heterozygous variants in the GH1 gene, including Exon2-5del, c.334T>C, c.291 + 1G>A, c.291 + 2T>A, 1.5 kb deletion, and 1.7 kb deletion, with four variants being novel. Four patients underwent human recombinant growth hormone (rhGH) replacement therapy, initiating treatment at a mean age of 4.6 ± 0.7 years. The mean height increase in patients was 1.21 ± 0.3 SDS in the first six months of treatment and 1.79 ± 0.15 SDS in the first year.

Conclusion

Our findings contribute to expanding the genotypic and phenotypic spectra of individuals with IGHD II.

IGF signaling pathway in bone and cartilage development, homeostasis, and disease

The skeleton plays a fundamental role in the maintenance of organ function and daily activities. The insulin-like growth factor (IGF) family is a group of polypeptide substances with a pronounced role in osteoblast differentiation, bone development, and metabolism. Disturbance of the IGFs and the IGF signaling pathway is inextricably linked with assorted developmental defects, growth irregularities, and jeopardized skeletal structure. Recent findings have illustrated the significance of the action of the IGF signaling pathway via growth factors and receptors and its interactions with dissimilar signaling pathways (Wnt/β-catenin, BMP, TGF-β, and Hh/PTH signaling pathways) in promoting the growth, survival, and differentiation of osteoblasts. IGF signaling also exhibits profound influences on cartilage and bone development and skeletal homeostasis via versatile cell-cell interactions in an autocrine, paracrine, and endocrine manner systemically and locally. Our review summarizes the role and regulatory function as well as a potentially integrated gene network of the IGF signaling pathway with other signaling pathways in bone and cartilage development and skeletal homeostasis, which in turn provides an enlightening insight into visualizing bright molecular targets to be eligible for designing effective drugs to handle bone diseases and maladies, such as osteoporosis, osteoarthritis, and dwarfism.

Growth hormone resistance induced by amino acid deprivation in fao cells is independent of FGF21

Adequate dietary intake of amino acids is imperative for normal animal growth. Our previous work using rat hepatocarcinoma Fao cells demonstrated that growth hormone (GH) resistance, coupled with a concurrent reduction in insulin-like growth factor 1 (Igf1) mRNA levels, may underlie the growth retardation associated with a low-protein diet (LPD). In this study, we investigated whether FGF21 contributes to liver GH resistance in Fao rat hepatoma cells under amino acid deprivation conditions. Mice subjected to an LPD exhibited growth retardation, compromised GH signaling in the liver, and decreased blood IGF-1 levels compared with those on a control diet. To assess the potential involvement of fibroblast growth factor (FGF) 21, produced in response to amino acid deficiency, in the development of GH resistance, we examined GH signaling and Igf1 mRNA levels in Fao cells cultured in amino acid-deprived medium. Despite the inhibition of Fgf21 expression by the integrated stress response inhibitor, an inhibitor of the eukaryotic initiation factor 2-activating transcription factor 4 pathway, GH resistance persisted in response to amino acid deprivation. Additionally, the introduction of FGF21 into the control medium did not impair either GH signaling or GH-induced Igf1 transcription. These data suggest that, in Fao cells, amino acid deprivation induces GH resistance independently of FGF21 activity. By shedding light on the mechanisms behind growth retardation-associated GH resistance linked to amino acid deficiencies, our findings provide valuable insights for clinicians in formulating effective treatment strategies for individuals facing these challenges.

Preliminary investigation into the genetic etiology of short stature in children through whole exon sequencing of the core family

A comprehensive survey was carried out to investigate the genetic etiology of short stature in children by whole exon sequencing of a core family cohort to find and study mutations in multiple genes to assess their potential correlations to low height in children. The study included 56 pediatric patients from the Department of Pediatrics at the Zhangzhou Affiliated Hospital of Fujian Medical University. The participants met strict inclusion criteria, including age, Han Chinese ethnicity, low height standard deviation score, and the absence of known causes for short stature. Core pedigrees were identified using exome sequencing. After sequencing, variations were categorized and interpreted according to a variety of factors, including inheritance, location, type, and disease-causing gene databases. Variants were verified by Sanger sequencing. Most of the 97 gene mutations were missense. ACAN, PHEX, and COL2A1 were the most common gene mutations. Copy number variations were identified, particularly associated with the PHEX gene. Protein functional studies revealed that the mutations had a considerable influence on disease-promoting damage. The chromosomal locations with the highest enrichment of these genes were chr12, chr5, and chr2. In conclusion, the study revealed numerous genetic changes that may substantially impact physiological processes and disease. These findings establish the basis for further investigations into their diagnostic and therapeutic capabilities.