A case of premature thelarche with no central cause or genetic variants within the estrogen receptor signaling pathway.

BACKGROUND: Premature thelarche is defined as breast development before 8 years of age. This is most often caused by central hormone disregulation and is accompanied by concurrent bone maturation. However, we present a case of premature thelarche with concurrent bone maturation without central hormone disregulation. Genes within the estrogen signaling pathway were examined for genetic changes which might be responsible for the clinical phenotype. PATIENT REPORT: A girl presented with breast development from 18 months of age with undetectable serum estrogens, prepubertal serum gonadotropins, advanced growth and skeletal maturation, but no increase of uterine size, thus presenting a premature thelarche variant. Serum estrogens remained below detectable limits until she entered into an unremarkable puberty at 12.1 years of age. No abnormalities or SNPs were found in the genes tested. CONCLUSION: We describe a case of premature thelarche which cannot be attributed to a central cause of abnormal hormone levels or to alterations in genes suspected for this phenotype. We conclude that other yet to be identified factors are involved in this unique case of premature thelarche.

Tall stature and duplication of the insulin-like growth factor I receptor gene.

Trisomy of 15q26-qter is frequently associated with tall stature and mental retardation. Here we describe a patient with such trisomy, without a partial monosomy of another chromosome. The tall stature in this patient is most probably caused by duplication of the IGF1R gene. A duplication of the IGF1R gene is not a frequent finding in patients with tall stature. In 38 patients with features of Sotos syndrome without NSD1 alterations, a duplication was found only once. This patient was already known to have an unbalanced 2;15 translocation. Looking for a duplication of the 15qter region is still worth consideration in patients with tall stature and features of Sotos syndrome without an NSD1 alteration, especially when there is craniosynostosis or marked speech delay.

Genetic disorders in the GH IGF-I axis in mouse and man.

Animal knockout experiments have offered the opportunity to study genes that play a role in growth and development. In the last few years, reports of patients with genetic defects in GH-IGF-I axis have greatly increased our knowledge of genetically determined causes of short stature. We will present the animal data and human reports of genetic disorders in the GH-IGF-I axis in order to describe the role of the GH-IGF-I axis in intrauterine and postnatal growth. In addition, the effects of the GH-IGF-I axis on the development and function of different organ systems such as brain, inner ear, eye, skeleton, glucose homeostasis, gonadal function, and immune system will be discussed. The number of patients with genetic defects in the GH-IGF-I axis is small, and a systematic diagnostic approach and selective genetic analysis in a patient with short stature are essential to identify more patients. Finally, the implications of a genetic defect in the GH-IGF-I axis for the patient and the therapeutic options will be discussed.

A variable degree of intrauterine and postnatal growth retardation in a family with a missense mutation in the insulin-like growth factor I receptor.

CONTEXT: The type 1 IGF-I receptor (IGF1R) mediates the biological functions of IGF-I. Binding of IGF-I to the IGF1R results in autophosphorylation of the intracellular beta-subunit and activation of intracellular signaling. OBJECTIVE: The objective of this study was to evaluate the functional characteristics of a novel IGF1R mutation and describe the phenotypic features of two patients with this mutation. DESIGN: The study was performed in a university hospital. PATIENTS: We describe a 35-yr-old female with mild intrauterine growth failure, progressive postnatal growth retardation, severe failure to thrive, and microcephaly. Her daughter was born with severe intrauterine growth retardation and also showed postnatal failure to thrive and microcephaly. RESULTS: We found a heterozygous G3148-->A nucleotide substitution in the IGF1R gene, changing a negatively charged glutamic acid at position 1050 into a positively charged lysine residue (E1050K). E1050 is a conserved residue in the intracellular kinase domain. Dermal fibroblasts of the mother showed normal binding of iodinated IGF-I, but autophosphorylation and activation of downstream signaling cascades upon challenging with IGF-I was markedly reduced. Consequently, the maximal [(3)H]thymidine incorporation upon challenge with a dose range of IGF-I was reduced compared with a panel of control cells (3.65 +/- 1.79-fold vs. 6.75 +/- 4.7-fold stimulation; P < 0.01). These data suggest that the mutation results in the inactivation of one copy of the IGF1R gene. CONCLUSIONS: These two patients support the key role for IGF-I in intrauterine and postnatal growth. The different phenotypes of these and earlier described patients may be associated with variability in IGF-I signaling. The degree of intrauterine growth retardation may be partially determined by the presence or absence of maternal IGF-I resistance.

Homozygous and heterozygous expression of a novel insulin-like growth factor-I mutation.

IGF-I is a key factor in intrauterine development and postnatal growth and metabolism. The secretion of IGF-I in utero is not dependent on GH, whereas in childhood and adult life, IGF-I secretion seems to be mainly controlled by GH, as revealed from studies on patients with GHRH receptor and GH receptor mutations. In a 55-yr-old male, the first child of consanguineous parents, presenting with severe intrauterine and postnatal growth retardation, microcephaly, and sensorineural deafness, we found a homozygous G to A nucleotide substitution in the IGF-I gene changing valine 44 into methione. The inactivating nature of the mutation was proven by functional analysis demonstrating a 90-fold reduced affinity of recombinantly produced for the IGF-I receptor. Additional investigations revealed osteoporosis, a partial gonadal dysfunction, and a relatively well-preserved cardiac function. Nine of the 24 relatives studied carried the mutation. They had a significantly lower birth weight, final height, and head circumference than noncarriers. In conclusion, the phenotype of our patient consists of severe intrauterine growth retardation, deafness, and mental retardation, reflecting the GH-independent secretion of IGF-I in utero. The postnatal growth pattern, similar to growth of untreated GH-deficient or GH-insensitive children, is in agreement with the hypothesis that IGF-I secretion in childhood is mainly GH dependent. Remarkably, IGF-I deficiency is relatively well tolerated during the subsequent four decades of adulthood. IGF-I haploinsufficiency results in subtle inhibition of intrauterine and postnatal growth.

Disturbances of growth and endocrine function after busulphan-based conditioning for haematopoietic stem cell transplantation during infancy and childhood.

It is generally assumed that busulphan/cyclophoshamide (Bu/Cy)-based conditioning regimens for haematopoietic stem cell transplantation (SCT) do not affect growth. We evaluated growth and endocrine function after Bu/Cy-based conditioning in 64 children without a history of irradiation. Mean height standard deviation scores remained stable, but unexplained disturbances of growth after SCT were found in 17/48 (35%) of the children without growth-limiting disorders (10/23 in patients treated for haematological malignancies). In 10 patients, growth hormone (GH) secretion status was evaluated, and insufficient GH secretion was diagnosed in four patients. Thyroid function was evaluable in 52 patients. Two developed antibody-mediated thyroid disorders and 10 (19%) compensated primary hypothyroidism. Gonadal function was evaluable in 21 patients and was normal in all seven patients treated with low-dose Bu (8 mg/kg), whereas seven of the 14 children receiving high-dose Bu (16-20 mg/kg) developed gonadal failure; the majority of these patients had not been exposed to gonadotoxic therapy prior to Bu/Cy. Of the 49 evaluable patients, 16 developed subclinical hyperparathyroidism. We conclude that, besides gonadal and thyroid dysfunction, impaired growth and hyperparathyroidism often occur after Bu/Cy conditioning for SCT and that growth impairment may be the result of insufficient GH secretion.

Molecular IGF-1 and IGF-1 receptor defects: from genetics to clinical management.

Molecular defects of the insulin-like growth factor 1 gene (IGF1) are rare in the human. Only three homozygous and two families with heterozygous mutations of the IGF1 gene have been described, resulting in a variable degree of intrauterine and postnatal growth retardation, microcephaly, developmental delay and deafness. Detailed genetic analysis and functional experiments have shown that IGF-1 plays a key role in pre- and postnatal growth and development in human. Eleven patients with heterozygous and 2 patients with compound heterozygous mutations in the type 1 IGF1 receptor gene (IGF1R) have been reported. Intrauterine and postnatal growth retardation, microcephaly and IGF-1 levels above the mean of age references are consistent findings in these patients, although IGF-1 levels can be low initially because of feeding problems. The first reported patients showed the most severe phenotype, but with the identification of additional patients the phenotype appears to be more variable. The functional effect of the defects has been studied by in vitro experiments. From these studies, receptor haploinsufficiency, decreased IGF1R biosynthesis, interference with ligand binding and transmembrane signaling, and disruption of the intrinsic tyrosine kinase activity have been suggested as possible mechanisms with a variable pathogenetic spectrum. Data on GH treatment in these children are limited, showing a poor to modest growth response.

Genetic analysis of GHR should contain sequencing of all coding exons and specific intron sequences, and screening for exon deletions.

BACKGROUND: The work-up of patients with clinical and/or biochemical features of growth hormone insensitivity (GHI) usually contains genetic analysis of the growth hormone receptor (GHR) gene, and if negative, of STAT5B, IGFALS and IGF1. In a previous report we described 2 siblings presenting with short stature, low IGF-1 levels, elevated GH secretion and no increase of IGF-1 after 1 week of GH administration. Repeated analysis of the GHR showed no abnormalities; however, further testing revealed a heterozygous STAT5B defect in both siblings. SUBJECTS AND METHODS: Two boys of Surinam-Hindustan origin showed growth failure up to the age of 6-7 years, followed by partial catch-up growth associated with increasing body mass index. Reanalysis of GHR including published intronic sequences was performed on the patients' DNA collected 7 years earlier. RESULTS: The heterozygous STAT5B variant proved to be functionally benign. A homozygous intronic mutation of the GHR, c.618+792A>G (IVS6+792A>G), was subsequently found, resulting in the activation of pseudoexon 6ψ, and explaining the GHI phenotype of the patients. CONCLUSION: An intronic GHR mutation should be considered in all patients with signs of GHI and no coding exon mutations, even if the phenotype is mild and even if other genetic variants have been found.

The severe short stature in two siblings with a heterozygous IGF1 mutation is not caused by a dominant negative effect of the putative truncated protein.

OBJECTIVE: While in previous studies heterozygosity for an Insulin-Like Growth Factor 1 (IGF1) defect only modestly decreased height and head circumference, we recently reported on two siblings with severe short stature with a maternally transmitted heterozygous duplication of 4 nucleotides, resulting in a frame shift and a premature termination codon in the IGF1 gene. In this paper we describe the structural and functional characteristics of the putative truncated IGF-I protein. DESIGN: Two children, their mother and maternal grandfather carried the mutation. In addition, two family members who were not affected were included in the study. Mutant (MT) IGF-I was synthesized in oxidized and reduced form using two methods. Neutral gel filtration studies were carried out with wild-type (WT) and synthetic MT IGF-I. Binding analysis of synthetic MT IGF-I to the IGF1R and insulin receptors were performed with EBNA-293 cells, stably transfected with the IGF-I receptor, and IM9 cells. L6 cells were used to examine the mitogenic potency and the potential antagonizing effect of synthetic MT IGF-I by [(3)H]-thymidine incorporation assays. RESULTS: In the sera of both the carriers and non-carriers the proportion of (125)I-IGF-I that was associated with the 150 kDa complex was somewhat less (varying between ~37 and ~52%) than in normal pooled serum (~53-~63%) and, instead, slightly increased amounts of radioactivity were eluted in the 40-50 kDa fraction (consisting of binary IGF-IGFBP complexes) or remained unbound. Synthetic MT IGF-I did not bind to the IGF-I receptor, nor antagonize the growth-promoting effect of IGF-I. It did bind to IGFBPs, but was barely incorporated into 150 kDa complexes. Because in all cases WT IGF-I immunoreactivity was recovered in one peak, corresponding to the MW of WT IGF-I, i.e. ~7.6 kDa, an interaction of circulating truncated mutant peptide with WT IGF-I is very unlikely. CONCLUSIONS: There is no evidence that the severe short stature associated with heterozygosity for this novel IGF1 mutation in children born from a mother with the same mutation is caused by a dominant negative effect of the truncated protein. We speculate that the growth failure is caused by a combination of partial IGF-I deficiency, placental IGF-I insufficiency, and other genetic factors.

Short stature associated with a novel heterozygous mutation in the insulin-like growth factor 1 gene.

CONTEXT: Homozygous IGF1 deletions or mutations lead to severe short stature, deafness, microcephaly, and mental retardation. Heterozygosity for an IGF-I defect may modestly decrease height and head circumference. OBJECTIVE: The objective of the study was to investigate the clinical features of heterozygous carriers of a novel mutation in the IGF1 gene in comparison with noncarriers in a short family and to establish the effect of human GH treatment. SUBJECTS: Two children, their mother, and their maternal grandfather carried the mutation and were compared with two relatives who were noncarriers. RESULTS: The two index cases had severe short stature (height sd score -4.1 and -4.6), microcephaly, and low IGF-I levels. Sequencing of IGF1 revealed a heterozygous duplication of four nucleotides, resulting in a frame shift and a premature termination codon. The mother and maternal grandfather had the same IGF1 mutation. Adult height (corrected for shrinking and secular trend) and head circumference sd score of carriers of the paternally transmitted mutation was -2.5 and -1.8, in comparison with -1.6 and 0.3 in noncarriers, respectively. After 2 yr of GH treatment, both index cases exhibited increased growth. CONCLUSIONS: Heterozygosity for this novel IGF1 mutation in children born from a mother with the same mutation, presumably in combination with other genetic factors for short stature, leads to severe short stature, which can be successfully treated with GH.

Genetic disorders in the growth hormone - insulin-like growth factor-I axis.

In the last few years, our knowledge of genetically determined causes of short stature has greatly increased by reports of challenging patients, who offered the opportunity to study genes that play a role in growth. Since the first paper that showed the etiology of Laron syndrome [Godowski PJ, et al: Proc Natl Acad Sci USA 1989;86:8083-8087], many mutations in the growth hormone (GH) receptor have been identified. Recently, new mutations or deletions have been found in several components of the GH-insulin-like growth factor-I (IGF-I) axis: a homozygous mutation of the GH1 gene, resulting in a bio-inactive GH; mutations in the STAT5b gene, which plays a major role in the GH signal transduction; a homozygous missense mutation in the IGF-I gene; heterozygous mutations in the IGF-I receptor gene and a homozygous deletion of the acid-labile subunit gene. In this mini review, we describe the clinical and biochemical features of these genetic defects. Genetic analysis has become essential in the diagnostic workup of a patient with short stature. However, regarding the time consuming nature of molecular analysis, it is important to carefully select the patient for specific genetic evaluation. To help in this selection process, we developed flowcharts, based on the recently described patients, that can be used as guidelines in the diagnostic process of patients with severe short stature of unknown origin.

Adult height corrected for shrinking and secular trend.

BACKGROUND: If in growth studies on adults of different ages and generations height standard deviation scores (SDS) is to be calculated, individual heights should be compared with the average height for that generation (corrected for secular trend) at that age (corrected for shrinking). AIM: To generate mathematical formulas for calculating adult height SDS corrected for shrinking and secular trend. SUBJECTS AND METHODS: Decline of height by age was modelled based on data derived from the Baltimore Longitudinal Study of Aging. Based on mean height of Dutch conscripts in 1917 and data from four consecutive nationwide growth studies (1955, 1965, 1980 and 1997), and assuming a constant male-female difference of 13 cm, the secular trend was modelled over 80 years. The average coefficient of variation was calculated from the last three Dutch nationwide growth studies. RESULTS: Height at 21 years of age can be estimated as current height t 0.042*(age - 21) -0.0015*(age - 21)2 for males, and current height + 0.039*(age - 21) + 0.0019*(age - 21)2 for females. Mean height of 21-year-olds between 1917 and 1997 is characterized by linear regression. The coefficient of variation was close to 3.8%. Adult height SDS is calculated by the equation (A - B)/(0.038B), where A is the estimated individual height at 21 years and B is the average height of 21-year-olds in that generation. CONCLUSION: For studies on adult height at various ages and in various generations, these equations can be used to reduce experimental noise.