Craniofacial and brain abnormalities in Laron syndrome (primary growth hormone insensitivity)

IGF-Binding Proteins and Their Proteolysis as a Mechanism of Regulated IGF Release in the Nervous Tissue

Insulin-like growth factors 1 and 2 (IGF-1 and IGF-2) play a key role in the maintenance of the nervous tissue viability. IGF-1 and IGF-2 exhibit the neuroprotective effects by stimulating migration and proliferation of nervous cells, activating cellular metabolism, inducing regeneration of damaged cells, and regulating various stages of prenatal and postnatal development of the nervous system. The availability of IGFs for the cells is controlled via their interaction with the IGF-binding proteins (IGFBPs) that inhibit their activity. On the contrary, the cleavage of IGFBPs by specific proteases leads to the IGF release and activation of its cellular effects. The viability of neurons in the nervous tissue is controlled by a complex system of trophic factors secreted by auxiliary glial cells. The main source of IGF for the neurons are astrocytes. IGFs can accumulate as an extracellular free ligand near the neuronal membranes as a result of proteolytic degradation of IGFBPs by proteases secreted by astrocytes. This mechanism promotes interaction of IGFs with their genuine receptors and triggers intracellular signaling cascades. Therefore, the release of IGF by proteolytic cleavage of IGFBPs is an important mechanism of neuronal protection. This review summarizes the published data on the role of IGFs and IGFBPs as the key players in the neuroprotective regulation with a special focus on the specific proteolysis of IGFBPs as a mechanism for the regulation of IGF bioavailability and viability of neurons.

Focal Epilepsy in Individuals with Laron Syndrome

OBJECTIVE

The aim of the study was to describe focal epilepsy in patients with Laron syndrome (LS).

METHODS

Data were retrieved from medical records of a single-center cohort of 75 patients with LS.

RESULTS

We describe for the first time 4 patients with concomitant focal epilepsy and LS. Two of them experienced episodes of status epilepticus. Electroencephalogram examination in all 4 patients showed interictal epileptiform discharges in the temporal regions. Three achieved long-term seizure freedom on antiseizure medications.

CONCLUSION

Patients with LS may be at risk of developing focal epilepsy, which seems to be unrelated to hypoglycemic episodes in childhood.

Sphenoid Bone Pneumatisation on Lateral Cephalograms of Patients With Neurofibromatosis Type 1

BACKGROUND/AIM

Neurofibromatosis type 1 (NF1) is an autosomal dominant hereditary disease that causes tumors and many developmental disorders, e.g., cranial dysplasia. The purpose of this retrospective study was to analyse the pneumatisation of the sphenoid bone in NF1.

PATIENTS AND METHODS

The anonymised lateral cephalograms of 166 NF1 patients and 166 age- and sex-matched controls were examined for anterior-posterior sphenoid pneumatisation. The patient group analysis considered whether the patients had been affected by a facial plexiform neurofibroma (FPNF).

RESULTS

Sphenoid pneumatisation was significantly lower in NF1 patients than in controls [odds ratio (OR)=0.184; 95%CI=0.11-0.32; p<0.001]. A FPNF statistically significantly reduced sinus formation in patients (OR=0.38; p=0.002).

CONCLUSION

The condition 'NF1' has an effect on sphenoid pneumatisation. The findings are relevant for planning surgical procedures in this region and confirm current concepts to evaluate NF1 as a histogenesis control gene. The examination technique and basis of calculation presented here are easy-to-use and low-irradiation exposure instruments for screening for differences in sphenoid bone pneumatisation in defined populations.

Laron syndrome - A historical perspective

Laron Syndrome (LS) [OMIm#262500], or primary GH insensitivity, was first described in 1966 in consanguineous Jewish families from Yemen. LS is characterized by a typical phenotype that includes dwarfism, obesity and hypogenitalism. The disease is caused by deletions or mutations of the GH-receptor gene, causing high serum GH and low IGF-I serum levels. We studied 75 patients from childhood to adult age. After early hypoglycemia due to the progressive obesity, patients tend to develop glucose intolerance and diabetes. The treatment is by recombinant IGF-I, which improves the height and restores some of the metabolic parameters. An unexpected finding was that patients homozygous for GH-R defects are protected from malignancy lifelong, not so heterozygotes or double heterozygote subjects. We estimate that there are at least 500 patients worldwide, unfortunately only few treated.

The Role of Insulin-Like Growth Factors and Insulin-Like Growth Factor-Binding Proteins in the Nervous System

The insulin-like growth factors (IGF-I and IGF-II) and their receptors are widely expressed in nervous tissue from early embryonic life. They also cross the blood brain barriers by active transport, and their regulation as endocrine factors therefore differs from other tissues. In brain, IGFs have paracrine and autocrine actions that are modulated by IGF-binding proteins and interact with other growth factor signalling pathways. The IGF system has roles in nervous system development and maintenance. There is substantial evidence for a specific role for this system in some neurodegenerative diseases, and neuroprotective actions make this system an attractive target for new therapeutic approaches. In developing new therapies, interaction with IGF-binding proteins and other growth factor signalling pathways should be considered. This evidence is reviewed, gaps in knowledge are highlighted, and recommendations are made for future research.

Neurotrophic Factors and Their Receptors Are Altered by the Mere Partial IGF-1 Deficiency

Neurotrophic factors (NTFs) are a relevant group of secreted proteins that modulate growth, differentiation, repair, and survival of neurons, playing a role in the maintenance of the synaptic unions, dendrites, and axons and also being crucial for peripheral nervous system development and regulating plasticity in the adult central nervous system. On the other hand, insulin-like growth factor 1 (IGF-1) has been ascertained multiple beneficial actions in the brain: neuro-development, -protection, -genesis and plasticity. To further investigate the possible mechanisms underlying IGF-1 deficiency in the establishment of neurological disease, microarray and reverse transcription polymerase chain reaction gene expression analyses coupled with in silico processing were performed in an experimental model of partial IGF-1 deficiency. Results show that the mere IGF-1 deficiency seems to be responsible for an altered expression of genes coding for neurotrophic factors (particularly ciliary neurotrophic factor and mesencephalic astrocyte-derived neurotrophic factor), their receptors and signaling pathways (specially RET). The presented findings support that IGF-1 deficiency might be involved in the establishment and progression of neurodegenerative disorders.

IGF-I deficiency, longevity and cancer protection of patients with Laron syndrome

Laron syndrome (LS) is a unique model of congenital IGF-I deficiency. It is characterized by dwarfism and obesity, and is caused by deletion or mutations of the growth hormone receptor (GH-R) gene. It is hypothesized that LS is an old disease originating in Indonesia and that the mutated gene spread to South Asia, the Middle East, the Mediterranean region and South America.

Fifty seven years of follow-up of the Israeli cohort of Laron Syndrome patients-From discovery to treatment

Clinical and laboratory investigations of dwarfed children newly Jewish immigrants from Yemen and Middle East and who resembled patients with isolated growth hormone deficiency were started by our group in 1958. In 1963 when we found that they have high serum levels of hGH, we knew that we had discovered a new disease of primary GH insensitivity. It was subsequently coined Laron Syndrome (LS, OMIM #262500). The etiopathogenesis was disclosed by 2 liver biopsies demonstrating a defect in the GH receptor. Subsequent investigations demonstrated deletions or mutations in the GHR gene. The defect lead to an inability of IGF-I generation, resulting in severe dwarfism, obesity, and other morphologic and biochemical pathologies due to IGF-I deficiency. With the biosynthesis of IGF-I in 1986, therapeutic trials started. Following closely our cohort of 69 patients with LS enabled us to study its features in untreated and IGF-I treated patients. This syndrome proved to be a unique model to investigate the effects of IGF-I dissociated from GH stimulation. In recent studies we found that homozygous patients for the GHR mutations are protected lifelong from developing malignancies, opening new directions of research.

What do cranial bones of LB1 tell us about Homo floresiensis?

Cranial vault thickness (CVT) of Liang Bua 1, the specimen that is proposed to be the holotype of Homo floresiensis, has not yet been described in detail and compared with samples of fossil hominins, anatomically modern humans or microcephalic skulls. In addition, a complete description from a forensic and pathological point of view has not yet been carried out. It is important to evaluate scientifically if features related to CVT bring new information concerning the possible pathological status of LB1, and if it helps to recognize affinities with any hominin species and particularly if the specimen could belong to the species Homo sapiens. Medical examination of the skull based on a micro-CT examination clearly brings to light the presence of a sincipital T (a non-metrical variant of normal anatomy), a scar from an old frontal trauma without any evident functional consequence, and a severe bilateral hyperostosis frontalis interna that may have modified the anterior morphology of the endocranium of LB1. We also show that LB1 displays characteristics, related to the distribution of bone thickness and arrangements of cranial structures, that are plesiomorphic traits for hominins, at least for Homo erectus s.l. relative to Homo neanderthalensis and H. sapiens. All the microcephalic skulls analyzed here share the derived condition of anatomically modern H. sapiens. Cranial vault thickness does not help to clarify the definition of the species H. floresiensis but it also does not support an attribution of LB1 to H. sapiens. We conclude that there is no support for the attribution of LB1 to H. sapiens as there is no evidence of systemic pathology and because it does not have any of the apomorphic traits of our species.

LESSONS FROM 50 YEARS OF STUDY OF LARON SYNDROME

OBJECTIVE

To describe the characteristics of untreated and recombinant insulin-like growth factor 1 (IGF-1)- treated patients with the Laron syndrome (LS) as seen in our clinic over a period of over 50 years. In 1966, we reported a new disease, characterized by dwarfism (-4 to -10 height standard deviation score) typical facial features, small head circumference, obesity, and small genitalia. They resembled congenital growth hormone (GH) deficiency but had high levels of serum human GH and low IGF-1. Since then, our cohort grew to 69 patients, consisting of Jews of oriental origin, Muslins, and Christians originating from the Middle East or Mediterranean area. Many belong to consanguineous families.

METHODS

Molecular genetic investigations revealed that these patients had deletions or mutations in the GH receptor gene, but only individuals homozygous for this defect express the disease, coined "Laron syndrome" (LS; Online Mendelian Inheritance in Man# 262500).

RESULTS

During childhood, LS patients grow slowly, have a retarded bone age and sexual development, but reach full sexual development. The treatment of LS is recombinant IGF-1, which stimulates the linear growth but increases the degree of obesity. Adult-age patients with congenital IGF-1 deficiency are protected from cancer but can develop insulin resistance, glucose intolerance, diabetes, and cardiovascular disease. Due to pathologic changes in the brain related to the type of molecular defect in the GH receptor, they vary in their intellectual capacity. A number of LS patients marry, and with help of pregestational genetic diagnosis, have healthy children.

CONCLUSION

LS is a unique disease model presenting a dissociation between GH and IGF-1 activity.

Three novel IGF1R mutations in microcephalic patients with prenatal and postnatal growth impairment

BACKGROUND

IGF1R gene mutations have been associated with varying degrees of intrauterine and postnatal growth retardation, and microcephaly.

OBJECTIVE

To identify and characterize IGF1R gene variations in a cohort of 28 Argentinean children suspected of having IGF-1 insensitivity, who were selected on the basis of the association of pre/postnatal growth failure and microcephaly.

METHODS

The coding sequence and flanking intronic regions of IGF1R gene were amplified and directly sequenced. Functional characterization was performed by two in vitro assays: 1) [Methyl-(3) H] thymidine incorporation into DNA in fibroblast cell primary cultures from patients and controls treated with IGF-1 for 16-24 h. 2) PI3K/Akt pathway was evaluated with phospho-Akt (Ser473) STAR ELISA Kit (Millipore) in fibroblast cultures from patients and controls stimulated with IGF-1 for 10 min. Prepubertal clinical and GH-IGF-1 axis evaluation was followed up.

RESULTS

We identified three novel heterozygous missense mutations in three unrelated patients, de novo p.Arg1256Ser, de novo p.Asn359Tyr and p.Tyr865Cys. In control cells, proliferation assay showed that IGF-1 significantly induced DNA synthesis at 20 h and Akt phosphorylation assay that it significantly stimulated phosphorylation after 10 min (P < 0·05 by anova and Bonferroni Tests). However, no significant increase was observed in any of the three patient fibroblasts in both functional studies. GH therapy growth response in two patients was inconsistent.

CONCLUSION

These variations led to failure of the IGF1R function causing pre- and postnatal growth retardation and microcephaly. Microcephaly should be considered in the evaluation of SGA patients, because it seems to favour the frequency of detection of IGF1R mutations.

Hearing status in adult individuals with lifetime, untreated isolated growth hormone deficiency

OBJECTIVE

To evaluate the hearing status of growth hormone (GH)-naive adults with isolated GH deficiency (IGHD) belonging to an extended Brazilian kindred with a homozygous mutation in the GH-releasing hormone receptor gene.

STUDY DESIGN

Cross-sectional.

SETTING

Divisions of Endocrinology and Otorhinolaryngology of the Federal University of Sergipe.

SUBJECTS AND METHODS

Twenty-six individuals with IGHD (age, 47.6 ± 15.1 years; 13 women) and 25 controls (age, 46.3 ± 14.3 years; 15 women) were administered a questionnaire on hearing complaints and hearing health history. We performed pure-tone audiometry, logoaudiometry, electroacoustic immittance, and stapedial reflex. To assess outer hair cell function in the cochlea, we completed transient evoked otoacoustic emissions (TEOAEs). To assess the auditory nerve and auditory brainstem, we obtained auditory brainstem responses (ABRs).

RESULTS

Misophonia and dizziness complaints were more frequent in those with IGHD than in controls (P = .011). Patients with IGHD had higher thresholds at 250 Hz (P = .005), 500 Hz (P = .006), 3 KHz (P = .008), 4 KHz (P = .038), 6 KHz (P = .008), and 8 KHz (P = .048) and mild high-tones hearing loss (P = .029). Stapedial reflex (P < .001) and TEOAEs (P = .025) were more frequent in controls. There were no differences in ABR latencies. Hearing loss in patients with IGHD occurred earlier than in controls (P < .001).

CONCLUSION

Compared with controls of the same area, subjects with untreated, congenital lifetime IGHD report more misophonia and dizziness, have predominance of mild high-tones sensorineural hearing loss, and have an absence of stapedial reflex and TEOAEs.

Sinus hypoplasia precedes sinus infection in a porcine model of cystic fibrosis

OBJECTIVES/HYPOTHESIS

Chronic sinusitis is nearly universal in humans with cystic fibrosis (CF) and is accompanied by sinus hypoplasia (small sinuses). However, whether impaired sinus development is a primary feature of loss of the cystic fibrosis transmembrane conductance regulator (CFTR) or a secondary consequence of chronic infection remains unknown. Our objective was to study the early pathogenesis of sinus disease in CF.

STUDY DESIGN

Animal/basic science research.

METHODS

Sinus development was studied in a porcine CF model.

RESULTS

Porcine sinus epithelia expressed CFTR and exhibited transepithelial anion transport. Disruption of the CFTR gene eliminated both. Sinuses of newborn CF pigs were not infected and showed no evidence of inflammation, yet were hypoplastic at birth. Older CF pigs spontaneously developed sinus disease similar to that seen in humans with CF.

CONCLUSIONS

These results define a role for CFTR in sinus development and suggest the potential of the CF pig as a genetic model of CF-sinus disease in which to test therapeutic strategies to minimize sinus-related CF morbidity.

The globe and orbit in Laron syndrome

BACKGROUND AND PURPOSE

Patients with LS have an inborn growth hormone resistance, resulting in failure to generate IGF-1. The purpose of this study was to evaluate the size of the eye and orbit in LS.

MATERIALS AND METHODS

We retrospectively reviewed the MR imaging of the brain in 9 patients with LS for the following parameters: axial diameter of the globe, interzygomatic distance, perpendicular distance from the interzygomatic line to margins of the globe, medial-to-lateral diameter of the orbit at the anterior orbital rim, distance from the anterior orbital rim to the anterior globe, maximal distance between the medial walls of the orbits, lateral orbital wall angle, lateral orbital wall length, and mediolateral thickness of the intraorbital fat in the most cranial image of the orbit. All measurements were made bilaterally. Twenty patients referred for MR imaging for unrelated reasons served as control subjects.

RESULTS

Compared with the control group, the patients with LS had a significantly smaller maximal globe diameter and shallower but wider orbits due to a shorter lateral wall, a smaller medial distance between the orbits, and a larger angle of the orbit. The ratio between the most anterior orbital diameter and the globe was greater than that in controls. The position of the globe was more anterior in relation to the interzygomatic line.

CONCLUSIONS

Shallow and wide orbits and small globes relative to orbital size are seen in LS and may be secondary to IGF-1 deficiency.

Diversity among African pygmies

Although dissimilarities in cranial and post-cranial morphology among African pygmies groups have been recognized, comparative studies on skull morphology usually pull all pygmies together assuming that morphological characters are similar among them and different with respect to other populations. The main aim of this study is to compare cranial morphology between African pygmies and non-pygmies populations from Equatorial Africa derived from both the Eastern and the Western regions in order to test if the greatest morphological difference is obtained in the comparison between pygmies and non-pygmies. Thirty three-dimensional (3D) landmarks registered with Microscribe in four cranial samples (Western and Eastern pygmies and non-pygmies) were obtained. Multivariate analysis (generalized Procrustes analysis, Mahalanobis distances, multivariate regression) and complementary dimensions of size were evaluated with ANOVA and post hoc LSD. Results suggest that important cranial shape differentiation does occur between pygmies and non-pygmies but also between Eastern and Western populations and that size changes and allometries do not affect similarly Eastern and Western pygmies. Therefore, our findings raise serious doubt about the fact to consider African pygmies as a homogenous group in studies on skull morphology. Differences in cranial morphology among pygmies would suggest differentiation after divergence. Although not directly related to skull differentiation, the diversity among pygmies would probably suggest that the process responsible for reduced stature occurred after the split of the ancestors of modern Eastern and Western pygmies.

Dental Development in Children with Growth Hormone Insensitivity Syndrome: Demirjian Analysis of Serial Panoramic Radiographs

Objective:

This study evaluates the effects of 8 years of insulinlike growth factor-I therapy on tooth development in patients with growth hormone insensitivity syndrome.

Methods:

Forty-nine panoramic radiographs were evaluated from eight patients (six boys, two girls). Seven teeth in the mandibular left region were graded according to the Demirjian system. Radiographs were taken at the start of insulinlike growth factor-I therapy and were continued at approximately yearly intervals for 8 years.

Results:

Three of six boys and one of two girls who began treatment with insulinlike growth factor-I at earlier ages experienced an increase in the rate of tooth development. One of six boys who began treatment with insulinlike growth factor-I at a later age had a slower rate of dental development. The patients had more rapid tooth maturation during the beginning of treatment. By the end of treatment, all patients had normal dental maturity for their age.

Conclusions:

Treatment of growth hormone insensitivity syndrome with insulinlike growth factor-I appears to lead to an increase in dental maturation, particularly in younger patients. After 8 years all patients had achieved normal dental development.

The development and pathologic processes that influence maxillary sinus pneumatization

The maxillary sinus is universally described as a pyramidal-shaped cavity in the maxilla. Hypoplasia, which can occur unilaterally or bilaterally, is graded by the authors by the degree of failure of descent below the nasal floor in achieving its position adjacent to the posterior dentition in the adult. Unlike early studies using plain X-rays, which considered pneumatization into the zygomatic recess and dental alveolus as criteria, the authors have adopted the above-cited parameters based on computed tomography (CT) imaging, which reveals that even when smaller the sinus retains a pyramidal configuration, although truncated. Rarely, the sinus is excessively pneumatized in the nonpathologic state. Review of the literature failed to reveal a comprehensive study of the conditions that alter maxillary sinus volume and configuration. Based on a retrospective review of 6,000 high resolution CT scans of the paranasal sinuses, the types and relative incidences of these conditions have been determined, and a classification system proposed. The mixed-sex sample group (= 2,540) was comprised of nonpediatric (adolescent and adult) and was of a polyethnic composition. Results showed that enlargement of the sinus is uncommonly encountered, and is produced by air (pneumocele) and mucus (mucocele) entrapment, or by benign tumors which have arisen in the sinus or adjacent maxilla and have grown intracavitarily, with the sinus walls expanding and remodeling to accommodate them. Reduction in size and volume is more frequent. Heredo-familial syndromic conditions reduce sinus size by impaired facial growth centers, or obliteration by dense osteosclerosis. Irradiation for neoplastic disease in the pediatric population similarly, directly effect growth centers, or impairs pituitary function. Another iatrogenic cause, direct surgical intervention (Caldwell-Luc procedure) almost universally alters sinus volume and shape by osteoneogenesis. Midfacial fractures involving the sinus also produce distortion by sclerosis as well as by malpositioning of bone fragments. The principal systemic disorders, sickle cell anemia and osteopetrosis, which diffusely effect medullary bone, do so either through compensatory marrow proliferation or sclerotic new bone formation, thus serving to produce maxillary enlargement and sinus obliteration. The greatest source of maxillary sinus distortion and destruction are neoplasms. Malignant sinonasal and oral cavity tumors produce bony erosion of the sinus walls, whereas benign odontogenic cysts remain external to the sinuses and compress it as they enlarge. Most odontogenic tumors produce external compression and remodeling. Fibro-osseous disorders similarly produce size and shape distortions by external impingement. Although diverse developmental and pathological conditions influence maxillary sinus morphology, there is a limited range of biologic response.

Abnormalities of the axial and proximal appendicular skeleton in adults with Laron syndrome (growth hormone insensitivity)

OBJECTIVE

To investigate abnormalities in the skeleton (with the exclusion of the skull, cervical spine, hands and feet) in patients with Laron syndrome, who have an inborn growth hormone resistance and congenital insulin-like growth factor-1 (IGF-1) deficiency.

DESIGN AND PATIENTS

The study group was composed of 15 untreated patients with Laron syndrome (seven male and eight female) aged 21-68 years. Plain films of the axial and appendicular skeleton were evaluated retrospectively for abnormalities in structure and shape. The cortical width of the long bones was evaluated qualitatively and quantitatively (in the upper humerus and mid-femur), and the cortical index was calculated and compared with published references. Measurements were taken of the mid-anteroposterior and cranio-caudal diameters of the vertebral body and spinous process at L3, the interpedicular distance at L1 and L5, and the sacral slope. Thoracic and lumbar osteophytes were graded on a 5-point scale. Values were compared with a control group of 20 healthy persons matched for age.

RESULTS

The skeleton appeared small in all patients. No signs of osteopenia were visible. The cortex of the long bones appeared thick in the upper limbs in 11 patients and in the lower limbs in four. Compared with the reference values, the cortical width was thicker than average in the humerus and thinner in the femur. The vertebral diameters at L3 and the interpedicular distances at L1 and L5 were significantly smaller in the patients than in the control subjects (P<0.001); however, at L5 the canal was wider, relative to the vertebral body. The study group had a higher rate of anterior osteophytes in the lumbar spine than the controls had, and their osteophytes were also significantly larger. In the six patients for whom radiographs of the upper extremity in its entirety were available on one film, the ulna appeared to be rotated. In one 22-year-old man, multiple epiphyses were still open.

CONCLUSION

Congenital IGF-1 deficiency leads to skeletal abnormalities characterized by small bones, narrow spinal canal, and delayed bone age. The limitation in elbow distensibility common to patients with Laron syndrome may be related to a marked retroversion of the humeral head.

Comparative skeletal features betweenHomo floresiensis and patients with primary growth hormone insensitivity (Laron syndrome)

Comparison between the skeletal remains of Homo floresiensis and the auxological and roentgenological findings in a large Israeli cohort of patients with Laron Syndrome (LS, primary or classical GH insensitivity or resistance) revealed striking morphological similarities, including extremely small stature and reduced cranial volume. LS is an autosomal recessive disease caused by a molecular defect of the Growth Hormone (GH) receptor or in the post-receptor cascades. Epidemiological studies have shown that LS occurs more often in consanguineous families and isolates, and it has been described in several countries in South East Asia. It is our conclusion that the findings from the island of Flores, which were attributed to a new species of the genus Homo, may in fact represent a local, highly inbred, Homo sapiens population in whom a mutation for the GH receptor had occurred.