Communication with young people in paediatric and adult endocrine consultations: an intervention development and feasibility study.

BACKGROUND: Communication is complex in endocrine care, particularly during transition from paediatric to adult services. The aims of this study were to examine the feasibility of interventions to support young people to interact with clinicians. METHODS: Development and evaluation of a complex intervention in 2 phases: Pre-intervention observational study; Intervention feasibility study. Purposive sample of recordings of 62 consultations with 58 young people aged 11-25 years with long-term endocrine conditions in two paediatric and two adult endocrine clinics. Proportion of time talked during consultations, number and direction of questions asked; Paediatric Consultation Assessment Tool (PCAT); OPTION shared decision making tool; Medical Information Satisfaction Scale (MISS- 21). Young people were invited to use one or more of: a prompt sheet to help them influence consultation agendas and raise questions; a summary sheet to record key information; and the www.explain.me.uk website. RESULTS: Nearly two thirds of young people (63%) chose to use at least one communication intervention. Higher ratings for two PCAT items (95% CI 0.0 to 1.1 and 0.1 to 1.7) suggest interventions can support consultation skills. A higher proportion of accompanying persons (83%) than young people (64%) directed questions to clinicians. The proportion of young people asking questions was higher (84%) in the intervention phase than in the observation phase (71%). CONCLUSIONS: Interventions were acceptable and feasible. The Intervention phase was associated with YP asking more questions, which implies that the availability of interventions could promote interactivity.

Integrating genetic and imaging investigations into the clinical management of congenital hyperinsulinism.

Congenital Hyperinsulinism (CHI) is a rare but important cause of hypoglycaemia in infancy. CHI is a heterogeneous disease, but has a strong genetic basis; a number of genetic causes have been identified with CHI in about a third of individuals, chiefly in the genes that code for the ATP sensitive K(+) channels (KATP ) in the pancreatic ß-cells. Rapid KATP channel gene testing is a critical early step in the diagnostic algorithm of CHI, with paternal heterozygosity correlating with the occurrence of focal lesions. Imaging investigations to diagnose and localize solitary pancreatic foci have evolved over the last decade with (18)F-DOPA PET-CT scanning as the current diagnostic tool of choice. Although clinical management of CHI has improved significantly with the application of genetic screening and imaging investigations, much remains to be uncovered. This includes a better understanding of the molecular mechanisms for dysregulated insulin release in those patients without known genetic mutations, and the development of biomarkers that could characterize CHI, including long-term prognosis and targeted treatment planning, i.e. 'personalised medicine'. From the perspective of pancreatic imaging, it would be important to achieve greater specificity of diagnosis not only for focal lesions but also for diffuse and atypical forms of the disease.

Likelihood of persistent GH deficiency into late adolescence: relationship to the presence of an ectopic or normally sited posterior pituitary gland.

OBJECTIVES: The presence of an ectopic posterior pituitary gland (EPP) in childhood is associated with isolated GH deficiency (IGHD) and multiple pituitary hormone deficiency. GHD in late adolescence has been defined as a peak GH level <5 microg/l. The aim of this study was to identify the likelihood of persistent GHD in late adolescence in patients with an EPP compared with those with a normally sited posterior pituitary (NPP). METHODS: In 18 patients with an EPP and 15 patients with an NPP, clinical, biochemical and radiographic data were collected. RESULTS: In the EPP vs. the NPP group, the change in peak GH levels at the end of growth was less (+0.4[95% confidence interval (CI) - 0.8 to 2.7] vs. +4.1[95%CI + 0.4 to +10.5] microg/l, P-value for ancova = 0.03, after adjustment for age and sex). Using a peak GH level of <5 microg/l as a cut-off for GHD, 66% of EPP subjects compared with 40% of NPP subjects had GHD (P = 0.3). Hundred per cent of EPP subjects had a peak GH level on retesting <10 microg/l, compared with 40% of NPP subjects (P < 0.001). CONCLUSION: It is important to document GH status at the end of growth, even if there is a structural abnormality of the hypothalamic-pituitary axis. The presence of an EPP compared to an NPP increases the likelihood of persistent GHD by 26%. As all EPP patients had a peak GH level of <10 microg/l, the cut-off for persistent GHD in late adolescence may need to be revised.

Extension of life-span with superoxide dismutase/catalase mimetics.

We tested the theory that reactive oxygen species cause aging. We augmented the natural antioxidant systems of Caenorhabditis elegans with small synthetic superoxide dismutase/catalase mimetics. Treatment of wild-type worms increased their mean life-span by a mean of 44 percent, and treatment of prematurely aging worms resulted in normalization of their life-span (a 67 percent increase). It appears that oxidative stress is a major determinant of life-span and that it can be counteracted by pharmacological intervention.

Skewed X inactivation is associated with phenotype in a female with adrenal hypoplasia congenita.

Adrenal hypoplasia congenita (AHC) can occur due to deletions or mutations in the DAX 1 (NR0B1) gene on the X chromosome (OMIM 300200). This form of AHC is therefore predominantly seen in boys. Deletion of the DAX 1 gene can also be part of a larger contiguous deletion including the centromeric dystrophin and glycerol kinase (GK) genes. We report a girl with a de novo deletion at Xp21.2 on the maternal chromosome, including DAX1, the GK gene and 3' end of the dystrophin gene, who presented with salt losing adrenal insufficiency and moderate developmental delay, but relatively mild features of muscular dystrophy. Investigation using the androgen receptor as a marker gene identified skewed inactivation of the X chromosome. In the patient's leucocytes, the paternal X chromosome was completely inactive, but in muscle 20% of the active chromosomes were of paternal origin. Thus skewed X inactivation (deletion on the active maternal X chromosome with an inactive paternal X chromosome) is associated with AHC in a female. Variability in X inactivation between tissues may account for the pronounced salt loss and adrenal insufficiency but mild muscular dystrophy.

Two years in growth hormone 2017-18.

This brief review highlights new studies in three areas of the GH field, namely diagnostics, therapeutics and biomarkers. The diagnosis of GH deficiency has always presented a challenge: there is no "gold standard" test of GH status, and GH levels during stimulation testing are affected by many factors that limit diagnostic accuracy. Two new approaches to diagnosis have been proposed: one involves a classical endocrine test of GH production using a GH secretagogue to test the Ghrelin axis, and shows promise in the diagnosis of adult GH deficiency. The other uses a completely different approach analysing the individual's gene expression profile as a surrogate for GH status with high levels of test accuracy. From the therapeutic aspect, there have been significant efforts to produce a long-acting (LA) GH on the premise that this will improve adherence and patient convenience. Aspects of LA-GH pharmacology are considered, and it will be interesting to see in future years what place LA-GH GH takes in the market. Long term surveillance is a vital part of therapeutics; recent studies across Europe have provided reassurance on the safety of recombinant human GH (r-hGH) for those with uncomplicated growth disorders, but do emphasise the need to continue observation through adulthood. The search for biomarkers that precisely reflect GH action in children and adults is an ongoing task. One of the newer bone markers that shows promise is a fragment of collagen type X which now requires further investigation in humans. In parallel with the diagnostic studies, gene expression profiles at the start of r-hGH treatment have been used to predict GH response in children with GHD and girls with Turner syndrome. These data are promising but need evaluation across a range of growth disorders. R-hGH is an effective, safe therapy used in both children and adults. There is however a need to continue to refine diagnosis, treatment and most importantly long-term pharmacovigilance to ensure that the right patients have the best treatment with robust safety profiles.

Associations with multiple pituitary hormone deficiency in patients with an ectopic posterior pituitary gland.

INTRODUCTION: The presence of an ectopic posterior pituitary gland (EPP) on magnetic resonance imaging (MRI) is associated with hypopituitarism with one or more hormone deficiencies. We aimed to identify risk factors for having multiple pituitary hormone deficiency (MPHD) compared to isolated growth hormone deficiency (IGHD) in patients with an EPP. METHODS: In 67 patients (45 male) with an EPP on MRI, the site (hypothalamic vs. stalk) and surface area (SA) [ x (maximum diameter/2) x (maximum height/2), mm(2)] of the EPP were recorded and compared in patients with IGHD and MPHD in relation to clinical characteristics. RESULTS: In MPHD (n = 32) compared to IGHD (n = 35) patients: age of presentation was younger (1.4 [0.1-10.7]vs. 4.0 [0.1-11.3] years, P = 0.005), major incidents during pregnancy were increased (47%vs. 20%, P = 0.02) as were admissions to a neonatal intensive care unit (NICU) (60%vs. 26%, P = 0.04), whilst EPP SA was lower (12.3 [2.4-34.6]vs. 25.7 [6.9-48.2] mm(2), P < 0.001). In patients with a hypothalamic (n = 56) compared to a stalk sited EPP (n = 11): prevalence of MPHD was greater (55%vs. 9%,P = 0.05) and EPP surface area was smaller (17.3 [2.4-48.2]vs. 25.3 [11.8-38.5] mm(2), P < 0.001). In regression analysis, after adjusting for age, presence of MPHD was associated with: major incidents during pregnancy (RR 6.8 [95%CI 1.2-37.7]), hypothalamic EPP site (RR 10.9 [1.0-123.9]) and small EPP SA (RR 2.5 [1.0-5.0] for tertiles of SA). CONCLUSION: In patients with an EPP, adverse antenatal events, size (small) and position (hypothalamic) of the posterior pituitary gland on MRI were associated with MPHD. These findings suggest that adverse factors during pregnancy may be important for the development of an EPP.

Idiopathic short stature: definition, epidemiology, and diagnostic evaluation.

Idiopathic short stature is a condition in which the height of the individual is more than 2 SD below the corresponding mean height for a given age, sex and population, in whom no identifiable disorder is present. It can be subcategorized into familial and non-familial ISS, and according to pubertal delay. It should be differentiated from dysmorphic syndromes, skeletal dysplasias, short stature secondary to a small birth size (small for gestational age, SGA), and systemic and endocrine diseases. ISS is the diagnostic group that remains after excluding known conditions in short children.

Management of the child born small for gestational age through to adulthood: a consensus statement of the International Societies of Pediatric Endocrinology and the Growth Hormone Research Society.

OBJECTIVE: Low birth weight remains a major cause of morbidity and mortality in early infancy and childhood. It is associated with an increased risk of health problems later in life, particularly coronary heart disease and stroke. A meeting was convened to identify the key health issues facing a child born small for gestational age (SGA) and to propose management strategies. PARTICIPANTS: There were 42 participants chosen for their expertise in obstetrics, peri- and neonatal medicine, pediatrics, pediatric and adult endocrinology, epidemiology, and pharmacology. EVIDENCE: Written materials were exchanged, reviewed, revised, and then made available to all. This formed the basis for discussions at the meeting. Where published data were not available or adequate, discussion was based on expert clinical opinions. CONSENSUS PROCESS: Each set of questions was considered by all and then discussed in plenary sessions with consensus and unresolved issues identified. The consensus statement was prepared in plenary sessions and then edited by the group chairs and shared with all participants. CONCLUSIONS: The diagnosis of SGA should be based on accurate anthropometry at birth including weight, length, and head circumference. We recommend early surveillance in a growth clinic for those without catch-up. Early neurodevelopment evaluation and interventions are warranted in at-risk children. Endocrine and metabolic disturbances in the SGA child are recognized but infrequent. For the 10% who lack catch-up, GH treatment can increase linear growth. Early intervention with GH for those with severe growth retardation (height sd score, <-2.5; age, 2-4 yr) should be considered at a dose of 35-70 microg/kg x d. Long-term surveillance of treated patients is essential. The associations at a population level between low birth weight, including SGA, and coronary heart disease and stroke in later life are recognized, but there is inadequate evidence to recommend routine health surveillance of all adults born SGA outside of normal clinical practice.

An intronic growth hormone receptor mutation causing activation of a pseudoexon is associated with a broad spectrum of growth hormone insensitivity phenotypes.

CONTEXT: Inherited GH insensitivity (GHI) is usually caused by mutations in the GH receptor (GHR). Patients present with short stature associated with high GH and low IGF-I levels and may have midfacial hypoplasia (typical Laron syndrome facial features). We previously described four mildly affected GHI patients with an intronic mutation in the GHR gene (A(-1)-->G(-1) substitution in intron 6), resulting in the activation of a pseudoexon (6Psi) and inclusion of 36 amino acids. OBJECTIVE: The study aimed to analyze the clinical and genetic characteristics of additional GHI patients with the pseudoexon (6Psi) mutation. DESIGN/PATIENTS: Auxological, biochemical, genetic, and haplotype data from seven patients with severe short stature and biochemical evidence of GHI were assessed. MAIN OUTCOME MEASURES: We assessed genotype-phenotype relationship. RESULTS: One patient belongs to the same extended family, previously reported. She has normal facial features, and her IGF-I levels are in the low-normal range for age. The six unrelated patients, four of whom have typical Laron syndrome facial features, have heights ranging from -3.3 to -6.0 sd and IGF-I levels that vary from normal to undetectable. We hypothesize that the marked difference in biochemical and clinical phenotypes might be caused by variations in the splicing efficiency of the pseudoexon. CONCLUSIONS: Activation of the pseudoexon in the GHR gene can lead to a variety of GHI phenotypes. Therefore, screening for the presence of this mutation should be performed in all GHI patients without mutations in the coding exons.

A low dose euglycemic infusion of recombinant human insulin-like growth factor I rapidly suppresses fasting-enhanced pulsatile growth hormone secretion in humans.

To determine if insulin-like growth factor I (IGF-I) inhibits pulsatile growth hormone (GH) secretion in man, recombinant human IGF-I (rhIGF-I) was infused for 6 h at 10 micrograms.kg-1.h-1 during a euglycemic clamp in 10 normal men who were fasted for 32 h to enhance GH secretion. Saline alone was infused during an otherwise identical second admission as a control. As a result of rhIGF-I infusion, total and free IGF-I concentrations increased three- and fourfold, respectively. Mean GH concentrations fell from 6.3 +/- 1.6 to 0.59 +/- 0.07 micrograms/liter after 120 min. GH secretion rates, calculated by a deconvolution algorithm, decreased with a t 1/2 of 16.6 min and remained suppressed thereafter. Suppression of GH secretion rates occurred within 60 min when total and free IGF-I concentrations were 1.6-fold and 2-fold above baseline levels, respectively, and while glucose infusion rates were < 1 mumol.kg-1.min-1. During saline infusion, GH secretion rates remained elevated. Infusion of rhIGF-I decreased the mass of GH secreted per pulse by 84% (P < 0.01) and the number of detectable GH secretory pulses by 32% (P < 0.05). Plasma insulin and glucagon decreased to nearly undetectable levels after 60 min of rhIGF-I. Serum free fatty acids, beta-hydroxybutyrate, and acetoacetate were unaffected during the first 3 h of rhIGF-I but decreased thereafter to 52, 32, and 50% of levels observed during saline. We conclude that fasting-enhanced GH secretion is rapidly suppressed by a low-dose euglycemic infusion of rhIGF-I. This effect of rhIGF-I is likely mediated through IGF-I receptors independently of its insulin-like metabolic actions.

Efficacy of a monthly compared to 3-monthly depot GnRH analogue (goserelin) in the treatment of children with central precocious puberty.

AIMS: To compare the efficacy of goserelin 10.8 mg (Zoladex LA-ZLA) administered 9-12 weekly with 3.6 mg (Zoladex-Z) given monthly in suppressing pubertal development, and effect on body mass index (BMI). METHODS: Children with central precocious puberty (CPP) treated with Z (n = 34) or ZLA (n = 28) were studied retrospectively. Pubertal scores and BMI SDS during 24 months' treatment were compared. RESULTS: To attain adequate pubertal suppression, more patients on ZLA than Z required increase in injection frequency (p = 0.02) and this was so for 7/8 patients with a structural aetiology for CPP on ZLA and 2/8 on Z. A greater proportion of patients on ZLA had BMI >+2 SDS before (p = 0.05), and at 18 and 24 months (p = 0.02 and 0.04). BMI SDS transiently increased during the first 6 months on ZLA (p = 0.04). CONCLUSION: Both Z and ZLA were effective in suppressing puberty. To achieve adequate suppression, increased injection frequency was more likely with ZLA than Z, and particularly in patients with structural defects. Children with CPP had an elevated BMI at the onset of therapy and ZLA had a transient positive influence on BMI.

A pilot interventional study to evaluate the impact of cholecalciferol treatment on HbA1c in type 1 diabetes (T1D).

BACKGROUND: Higher 25(OH)D3 levels are associated with lower HbA1c, but there are limited UK interventional trials assessing the effect of cholecalciferol on HbA1c. AIMS: (1) To assess the baseline 25(OH)D3 status in a Manchester cohort of children with type 1 diabetes (T1D). (2) To determine the effect of cholecalciferol administration on HbA1c. METHODS: Children with T1D attending routine clinic appointments over three months in late winter/early spring had blood samples taken with consent. Participants with a 25(OH)D3 level <50 nmol/L were treated with a one-off cholecalciferol dose of 100,000 (2-10 years) or 160,000 (>10 years) units. HbA1c levels before and after treatment were recorded. RESULTS: Vitamin D levels were obtained from 51 children. 35 were Caucasian, 11 South Asian and 5 from other ethnic groups. 42 were vitamin D deficient, but 2 were excluded from the analysis. All South Asian children were vitamin D deficient, with mean 25(OH)D3 of 28 nmol/L. In Caucasians, there was a negative relationship between baseline 25(OH)D3 level and HbA1c (r = -0.484, P < 0.01). In treated participants, there was no significant difference in mean HbA1c at 3 months (t = 1.010, P = 0.328) or at 1 year (t = -1.173, P = 0.248) before and after treatment. One-way ANCOVA, controlling for age, gender, ethnicity, BMI and diabetes duration showed no difference in Δ HbA1c level. CONCLUSION: We report important findings at baseline, but in children treated with a stat dose of cholecalciferol, there was no effect on HbA1c. Further studies with larger sample sizes and using maintenance therapy are required.

Controversies in the diagnosis and management of growth hormone deficiency in childhood and adolescence.

Growth hormone deficiency (GHD) is a rare but important cause of short stature in childhood with a prevalence of 1 in 4000. The diagnosis is currently based on an assessment of auxology along with supporting evidence from biochemical and neuroradiological studies. There are significant controversies in the diagnosis and management of GHD. Growth hormone (GH) stimulation tests continue to play a key role in GHD diagnosis but the measured GH concentration can vary significantly with stimulation test and GH assay used, creating difficulties for diagnostic accuracy. Such issues along with the use of adjunct biochemical markers such as IGF-I and IGFBP-3 for the diagnosis of GHD, will be discussed in this review. Additionally, the treatment of GHD remains a source of much debate; there is no consensus on the best mechanism for determining the starting dose of GH in patients with GHD. Weight and prediction based models will be discussed along with different mechanisms for dose adjustment during treatment (auxology or IGF-I targeting approaches). At the end of growth and childhood treatment, many subjects diagnosed with isolated GHD re-test normal. It is not clear if this represents a form of transient GHD or a false positive diagnosis during childhood. Given the difficulties inherent in the diagnosis of GHD, an early reassessment of the diagnosis in those who respond poorly to GH is to be recommended.

Consensus statement on the management of the GH-treated adolescent in the transition to adult care.

The European Society for Paediatric Endocrinology held a consensus workshop in Manchester, UK in December 2003 to discuss issues relating to the care of GH-treated patients in the transition from paediatric to adult life. Clinicians experienced in the care of paediatric and adult patients on GH treatment, from a wide range of countries, as well as medical representatives from the pharmaceutical manufacturers of GH participated.

60 YEARS OF NEUROENDOCRINOLOGY: The hypothalamo-GH axis: the past 60 years.

At the time of the publication of Geoffrey Harris's monograph on 'Neural control of the pituitary gland' 60 years ago, the pituitary was recognised to produce a growth factor, and extracts administered to children with hypopituitarism could accelerate growth. Since then our understanding of the neuroendocrinology of the GH axis has included identification of the key central components of the GH axis: GH-releasing hormone and somatostatin (SST) in the 1970s and 1980s and ghrelin in the 1990s. Characterisation of the physiological control of the axis was significantly advanced by frequent blood sampling studies in the 1980s and 1990s; the pulsatile pattern of GH secretion and the factors that influenced the frequency and amplitude of the pulses have been defined. Over the same time, spontaneously occurring and targeted mutations in the GH axis in rodents combined with the recognition of genetic causes of familial hypopituitarism demonstrated the key factors controlling pituitary development. As the understanding of the control of GH secretion advanced, developments of treatments for GH axis disorders have evolved. Administration of pituitary-derived human GH was followed by the introduction of recombinant human GH in the 1980s, and, more recently, by long-acting GH preparations. For GH excess disorders, dopamine agonists were used first followed by SST analogues, and in 2005 the GH receptor blocker pegvisomant was introduced. This review will cover the evolution of these discoveries and build a picture of our current understanding of the hypothalamo-GH axis.

Activation of the signal transducers and activators of transcription signaling pathway by growth hormone (GH) in skin fibroblasts from normal and GH binding protein-positive Laron Syndrome children.

We have previously described two families (H and M) with GH binding protein-positive Laron Syndrome (LS), proposed to have one or more post GHR signaling defects. In the present study, we have examined whether the signal transducers and activators of transcription (STAT) pathway is activated by GH in skin fibroblast cultures established from these LS children, to determine the level(s) at which GH insensitivity has occurred. On immunoblots, both normal and LS fibroblasts express JAK2 and STATs 1, 3, and 5. GH induced rapid tyrosine phosphorylation of a protein at approximately 93 kDa in normal fibroblasts, and Western blotting with STAT-specific antibodies revealed STAT5 activation (phosphorylation) by GH. To determine further the identity and the DNA binding characteristics of the STAT proteins that were activated by GH, EMSAs were performed using three DNA elements known to bind STAT proteins; m67, the high affinity c-sis-inducible element (SIE), the interferon response element (IRE), and the lactogenic hormone-responsive region (LHRR). GH failed to induce protein binding to the SIE or IRE in normal skin fibroblasts but did induce the formation of a specific complex with the LHRR. Induction by GH of this LHRR/protein complex, which could be supershifted partially by anti-STAT1 antisera and completely by anti-STAT5 antisera, was transient, maximal between 10 and 30 min and reduced by 60 min. GH also induced distinct LHRR/protein complexes in mouse 3T3-F442A fibroblasts and in human IM-9 lymphocytes, but supershift analysis revealed that these complexes contained STAT5 but not STAT1. Whereas no binding to the LHRR was observed in GH-treated H fibroblasts, GH induced binding to this element in M fibroblasts. These results demonstrate that 1) the JAK-STAT pathway is activated by GH in normal fibroblasts and that STATs 1 and 5 have a role in GH-dependent signaling in these cells; 2) GH activation of DNA/STAT binding is cell type- and species-specific; and 3) GH failed to activate the STAT pathway in H fibroblasts but induced STAT signaling in M fibroblasts, indicating that the site of GH resistance in the latter is likely to be located within another GH signaling pathway. These fibroblast cultures therefore provide unique models with which to further our understanding of the mechanisms of human GH signaling.

Growth hormone stimulation of the mitogen-activated protein kinase pathway is cell type specific.

The GH receptor is a member of the cytokine receptor superfamily. Studies in the 3T3-F442A mouse preadipocyte have shown that GH activates the Janus kinase (JAK2), the signal transducers and activators of transcription (STAT1, -3, and -5), and mitogen-activated protein (MAP) kinase. Our previous studies in the human IM-9 lymphocyte have shown that GH activates JAK2 and only STAT5 (not STAT1 or -3). In the studies presented here, we have investigated activation of the MAP kinase (MAPK) pathway in the IM-9 lymphocyte. Western blotting with antiphosphotyrosine-, anti-MAPK-, and anti-phospho-MAPK-specific antibodies as well in vitro kinase assays using a synthetic peptide substrate demonstrate that although GH (200 ng/ml) activates MAPK in 3T3-F442A cells (at 5 and 10 min of treatment), it does not activate MAPK in IM-9 lymphocytes at time points ranging from 5-60 min. Nevertheless, the phorbol ester phorbol 12-myristate 13-acetate (50 ng/ml) does activate MAPK in the IM-9 cell, and immunoprecipitation with specific antibodies indicates that this activation occurs through c-Raf-1. Although the 52- and 66-kDa forms of the adapter protein Shc are tyrosine phosphorylated in response to GH treatment in 3T3-F442A cells, we demonstrate that the predominant forms in IM-9 cells are the 52- and 46-kDa forms, and neither is tyrosine phosphorylated in response to GH. These studies further elucidate the differential signaling by GH in two cell types.

Human skin fibroblasts as a model of growth hormone (GH) action in GH receptor-positive Laron's syndrome.

Congenital GH insensitivity (Laron's syndrome, LS) is often associated with a dysfunctional GH receptor (GHR) causing complete insensitivity to GH and absent serum GH-binding protein (GHBP). However, a proportion of children with LS have normal GHBP levels. We have identified four girls from two families with this condition (height SD score, -3.4 to -6.8) and undertaken studies on 1) their GHR genes and 2) their GH responses in cultured skin fibroblasts to define the etiology of their GH insensitivities. No GHR gene mutations were identified in one family. In the other family, the affected siblings, an unaffected brother, and the father were heterozygous for a point mutation within exon 6 (D152H). In addition, use of intron 9 haplotypes to determine linkage to the GHR gene implied inheritance of different maternal GHR alleles in the two affected girls of the latter family. It is unlikely, therefore, that the D152H mutation alone could account for the LS phenotype. End points of GH action [DNA synthesis, insulin-like growth factor-binding protein-3 (IGFBP-3) messenger RNA (mRNA) and peptide production] in skin fibroblast cultures established from three of the LS subjects and four normal children were examined. Whereas normal fibroblasts incorporated [3H]thymidine dose dependently in response to 10-1000 ng/ml GH (increment at 1000 ng/ml, 77 +/- 19%), LS fibroblasts failed to respond significantly above basal levels (P < 0.01). In normal fibroblasts, IGFBP-3 mRNA and peptide increased maximally at 48 h in response to 200 ng/ml GH, as determined by ribonuclease protection assay, Western ligand blotting, and RIA. In comparison, LS fibroblasts produced significantly less IGFBP-3 peptide than normal fibroblasts in response to GH, whereas IGFBP-3 mRNA failed to increase above basal levels. These studies have shown that 1) cultured human skin fibroblasts can be used to define the end points of GH action; 2) fibroblast cultures from the LS children show absent or reduced responses to GH; and 3) GH insensitivity in these children does not appear to be caused exclusively by GHR mutations, but is probably due to dysfunctional GHR signalling. Such patients may prove particularly important to elucidation of the key events in GH signaling.