Giuseppe Scirè

Molecular Analysis of the GNAS1 Gene for the Correct Diagnosis of Albright Hereditary Osteodystrophy and Pseudohypoparathyroidism

Pseudohypoparathyroidism (PHP) is a heterogeneous disease characterized by PTH resistance and classified as types Ia, Ib, Ic, and II, according to its different pathogenesis and phenotype. PHP-Ia patients show Gsα protein deficiency, PTH resistance, and typical Albright hereditary osteodystrophy (AHO). Heterozygous mutations in the GNAS1 gene encoding the Gsα protein have been identified both in PHP-Ia and in pseudopseudohypoparathyroidism (PPHP), a disorder with isolated AHO. A single GNAS1 mutation may be responsible for both PHP-Ia and PPHP in the same family when inherited from the maternal and the paternal allele, respectively, suggesting that GNAS1 is an imprinted gene. To evaluate whether molecular diagnosis is a useful tool to characterize AHO and PHP when testing for Gsα activity and PTH resistance is not available, we have performed GNAS1 mutational analysis in 43 patients with PTH resistance and/or AHO. Sequencing of the whole coding region of the GNAS1 gene identified 11 mutations in 18 PHP patients, eight of which have not been reported previously. Inheritance was ascertained in 13 cases, all of whom had PHP-Ia: the mutated alleles were inherited from the mothers, who had AHO (PPHP), consistent with the proposed imprinting mechanism. GNAS1 molecular analysis confirmed the diagnosis of PHP-Ia and PPHP in the mutated patients. Our results stress the usefulness of this approach to obtain a complete diagnosis, expand the GNAS1 mutation spectrum, and illustrate the wide mutation heterogeneity of PHP and PHP-Ia.

Height velocity and IGF‐I assessment in the diagnosis of childhood onset GH insufficiency: do we still need a second GH stimulation test?

objective The diagnosis of GH insufficiency (GHI) in childhood is not straightforward. Our aim was to test the sensitivity and specificity of height velocity (HV), IGF‐I, IGFBP‐3 and GH stimulation tests alone or in combination in the diagnosis of GHI.

Insulin Resistance and Insulin-Like Growth Factors in Children with Intrauterine Growth Retardation

Aims: To investigate (a) the prevalence of insulin resistance in children with intrauterine growth retardation (IUGR); (b) whether catch-up growth is associated with a higher risk of insulin resistance; (c) the insulin-like growth factor (IGF) system status. Methods: 49 children with IUGR aged 9.1 ± 3.3 years underwent anthropometric measurements, and assessment of insulin resistance and IGF system parameters. A fasting glucose/insulin ratio (G/I) <6 was chosen as suggestive of insulin resistance. Results: 11/49 (22%) children had a G/I <6. Postnatal growth closely correlated with birth size and actual body mass index (BMI). None of the insulin resistance parameters was related to linear growth and BMI. Liver function markers were significantly related to insulin sensitivity status. The IGF system status was normal and did not correlate with insulin resistance indicators. Conclusions: (a) Children with IUGR have a high prevalence of reduced insulin sensitivity; (b) postnatal catch-up growth is related to intrauterine growth and actual nutritional status; (c) insulin sensitivity status is not related to postnatal growth but to liver function; (d) IGF system is normal and not related to the insulin resistance parameters during childhood.

Long‐term treatment with growth hormone improves final height in a patient with Pallister‐Hall syndrome

Pallister-Hall syndrome is a disorder of development consisting of hypothalamic hamartoma, pituitary dysfunction, central polydactyly and visceral malformations. This disorder is inherited as an autosomal dominant trait and is caused by mutations of the GLI3 gene encoding a zinc finger transcription factor. We describe a case of Pallister-Hall syndrome with growth hormone neurosecretory dysfunction, successfully treated with growth hormone until attainment of final height. We conclude that children with Pallister-Hall syndrome and short stature be evaluated carefully for spontaneous somatotropic function and, if necessary, treated with growth hormone.

Catch-up growth in body mass index is associated neither with reduced insulin sensitivity nor with altered lipid profile in children born small for gestational age

Objective: Low birth weight is a risk factor for coronary heart disease. Persons who have coronary events as adults tend to have been small at birth and thin at 2 yr of age, after which they tended to increase their body mass index (BMI). Our aim was to determine whether BMI gain is associated to alterations in insulin sensitivity and/or lipid profile in children born small for gestational age (SGA). Design: Retrospective case-control study. Methods: We studied 78 children (mean age 7.8±2.5 yr): 26 SGA children with catch-up growth in BMI (CGB-SGA) (BMI= 10th to 75th centile), 26 SGA without catch-up growth (NCGB-SGA) (BMI<10th centile), and 26 appropriate for gestational age (AGA) control children (BMI: 10th to 75th centile). For each CGB-SGA child, we selected an NCGB-SGA and an AGA child of the same gender, age (with-in 1 yr), and pubertal status. SGA children were also subdivided into 2 groups according to post-natal catch-up growth in height (CGH). Results: Glucose was significantly lower in NCGBSGA than AGA group (p=0.02). No significant differences in fasting insulin, fasting glucose/insulin ratio, homeostasis model assessment, quantitative insulin-sensitivity check index, and lipid profile were found among the 3 groups. HDL-cholesterol proved significantly reduced in SGA children with post-natal CGH (p=0.02). Conclusions: Our findings do not support the hypothesis of early alterations in insulin sensitivity and lipid metabolism in CGB-SGA subjects during childhood provided that BMI remains within the normal range. Finally, the finding of reduced HDL-cholesterol levels in CGH-SGA children suggests detrimental metabolic effects of the height gain.

Low Birth Weight for Gestational Age Associates with Reduced Glucose Concentrations at Birth, Infancy and Childhood

Background/Aims: Our aim was to investigate glucose homeostasis, insulin sensitivity and insulin-like growth factor (IGF) system status in children born small for gestational age (SGA). Methods: A case-control study was carried out at birth, infancy and childhood, comparing SGA with children appropriate for gestational age strictly matched for age, gender, pubertal status and body mass index. Ninety newborns, 52 infants, and 68 children were studied. Fasting insulin (IF), fasting glucose (GF) to IF ratio (GF/IF), the homeostasis model assessment of insulin sensitivity, the quantitative insulin sensitivity check index, insulinogenic index and the triglyceride/high-density lipoprotein-cholesterol ratio were measured. IGF-I, IGF-binding protein-3 and the IGF-I/IGF-binding protein-3 molar ratio were assessed. Results: Glucose concentrations were lower in SGA newborns (p < 0.0001), infants (p = 0.01), and children (p = 0.001). Birth weight correlated with glucose levels at birth (r = 0.59, p < 0.0001), 12 months (r = 0.29, p = 0.04) and childhood (r = 0.44, p < 0.0001). Conclusion: Our results provide evidence for a developmental adaptation of glucose metabolism in SGA children leading to reduced glucose concentrations.

Growth Hormone and Dysmorphic Syndromes

In order to study the pathogenesis of short stature in some of the best known and most frequent dysmorphic syndromes, we have reviewed the most significant studies conducted on somatrotropin secretion and on response to replacement treatment with human growth hormone in pediatric patients. In particular, the study examines the results presented in the literature, and in a few of our cases, those obtained with regard to Noonan, Silver-Russell and Prader-Willi syndrome patients, to achondroplasia and hypochondroplasia patients, and to Down syndrome patients. Finally, we shall present a review of a few, less frequent dysmorphic syndromes with short stature, in which a growth hormone deficiency has been diagnosed and replacement treatment attempted.

Responses to GHRH plus arginine test are more concordant with IGF-I circulating levels than responses to arginine and clonidine provocative tests

BACKGROUND/OBJECTIVE Although pharmacological GH stimulation tests are still considered the gold standard for GH deficiency (GHD) diagnosis, they are burdened by poor specificity. The majority of children diagnosed as having GHD show normal GH responses when re-tested at the end of growth, thus questioning the initial diagnosis. We evaluated the concordance between IGF-I levels and GH responses to provocative tests. METHODS We analyzed 105 GHRH plus arginine tests, 79 arginine tests, and 124 clonidine tests performed in 192 short children. IGF-I levels ≤-2SD score (SDS) were considered suggestive for high likelihood of GHD. The percentage of positive and negative results for each test was determined and compared with IGF-I levels, clinical follow-up and response to therapy. RESULTS In children with IGF-I>-2SDS the arginine test showed a concordance rate of 6.9%, the clonidine test of 28.6%, and GHRH plus arginine test of 70%. In children with IGF-I≤-2SDS the concordance was 96.1%, 85.7%, and 46.4%, respectively. The overall concordance was 66.7% for GHRH plus arginine, 42.7% for clonidine, and 27.8% for arginine tests. CONCLUSION Our results suggest that GHRH plus arginine test provides the best concordance with the assessment of IGF-I levels thus suggesting that the combination of the two procedures may significantly reduce the need of a second provocative test.

Retinol-binding protein 4 in neonates born small for gestational age.

Background: Retinol-binding protein 4 (RBP4) is an adipocyte-derived ‘signal’ that may contribute to the pathogenesis of insulin resistance and Type 2 diabetes. The relationship of RBP4 with insulin resistance and metabolic risk in human beings has been the subject of several studies. Subjects born small for gestational age (SGA) are at risk of insulin resistance and Type 2 diabetes. Though RBP4 could represent an early marker of insulin resistance, to date, none have determined RBP4 in SGA children. Aim: Our aim was to measure RBP4 concentrations in cord blood of SGA newborns compared with those in children born with a birth weight appropriate for gestational age (AGA) and to determine whether serum RBP4 levels at birth correlate with insulin sensitivity markers. Subjects and methods: Sixty-four newborns, 17 born SGA (mean gestational age: 36.4±2.1 weeks), and 47 born AGA (mean gestational age: 37.0±3.6 weeks) were studied. The main outcome measures included anthropometry, lipid profile, insulin, homeostasis model assessment, quantitative insulin-sensitivity check index, adiponectin, and RBP4. Results: RBP4 concentrations were significantly reduced in SGA newborns (p<0.002). No relationship was found between RBP4 and insulin sensitivity parameters. Stepwise regression analysis revealed that birth weight was the major predictor of RBP4 serum concentrations (p<0.001). Conclusion: RBP4 is reduced in SGA newborns, birth weight representing the major determinant of RBP4 concentrations, and is not related to insulin sensitivity. No significant difference in adiponectin levels and insulin sensitivity markers was found between SGA and AGA neonates.

Brain Magnetic Resonance Imaging as First-Line Investigation for Growth Hormone Deficiency Diagnosis in Early Childhood.

Background/Aims: The diagnosis of growth hormone (GH) deficiency (GHD) in infancy and early childhood is not straightforward. GH stimulation tests are unsafe and unreliable in infants, and normative data are lacking. This study aims to investigate whether brain magnetic resonance imaging (MRI) may replace GH stimulation tests in the diagnosis of GHD in children younger than 4 years. Methods: We examined a retrospective cohort, with longitudinal follow-up, of 68 children consecutively diagnosed with GHD before the age of 4 years. The prevalence of hypothalamic-pituitary (HP) alterations at MRI and the associations with age and either isolated GHD (IGHD) or multiple pituitary hormone deficiency (MPHD) were assessed. Results: The prevalences of IGHD and MPHD were 54.4 and 45.6%, respectively. In the first group, brain MRI showed abnormalities in 83.8%: isolated pituitary hypoplasia in 48.7% and complex defects in 35.1%. In patients with MPHD, MRI showed complex alterations in 100%. All children younger than 24 months showed HP MRI abnormalities, regardless of the diagnosis. Complex defects were found in 94% of patients younger than 12 months and in 75% of patients between 13 and 24 months. Conclusion: Our data suggest that brain MRI may represent the first-line investigation for diagnosing GHD in infancy and early childhood.