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C Camacho-Hübner

Publications and source records attributed to C Camacho-Hübner.

At least 19 recordsLinked to original sources
PubMed2006

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.

Adolescent↗
PubMed2005

IGFs and IGFBPs in GH insensitivity.

IGF-I, IGFBP-3 and ALS are GH-dependent peptides and their production is disturbed in states of GH insensitivity. This chapter explores the relative degrees of IGF-I, IGFBP-3 and ALS deficiency across the spectrum of GH insensitivity. In classical GH insensitivity syndrome (GHIS), known as Laron syndrome, due to GH receptor (GHR) deficiency, serum IGF-I, IGFBP-3 and ALS are severely reduced with inability to produce these peptides during an IGF-I generation test. Across the spectrum of severity of GHR defects, some patients have short stature and normal facial appearance, so-called partial or non-classical GH insensitivity. In these cases the IGF-I, IGFBP-3 deficiency is less severe. A positive relationship exists between height SDS and IGFBP-3 SDS (r2 = 0.45, p < 0.001) in patients from the European series with GHIS. In a new series of GHIS cases (n = 36) there was a significant difference in IGFBP-3 and ALS (p < 0.05) between classical (n = 25) and non-classical cases (n = 11). IGF-I, IGFBP-3 and ALS were significantly higher (p < 0.05) in pubertal compared with pre-pubertal subjects in the same series. In idiopathic short stature (ISS), heterozygous mutations of the GHR may have a dominant negative effect. ISS patients have lower IGF-I levels than the normal population. In 21 cases, mean IGF-I SDS was -1.39 (-2.4 to -1.16) and IGFBP-3; -0.45 (-1.13 to 0.38). However, IGF-I and IGFBP-3 responses in the IGF-I generation test were generally normal. In acquired GHI due to chronic illness such as Crohn's disease, juvenile arthritis and cystic fibrosis, IGF-I deficiency is present, although IGFBP-3 is usually normal. In summary, assessment of IGF-I, IGFBP-3 and ALS contributes to diagnosis in GH insensitivity states. In our experience, IGF-I is more sensitive to disturbance of GH action that IGFBP-3, however in severe GHIS cases, IGF-I is usually undetectable and measurement of IGFBP-3 is valuable as a guide to the severity of the biological defect.

Biomarkers↗
PubMed2004

Standard and low-dose IGF-I generation tests and spontaneous growth hormone secretion in children with idiopathic short stature.

OBJECTIVE: Abnormalities in the GH-IGF-I axis, consistent with GH insensitivity (GHI), have been reported in some patients with idiopathic short stature (ISS). The standard IGF-I generation test (IGFGT) has not demonstrated mild GHI in subjects with ISS. The aim of this study was to investigate the GH-IGF-I axis in ISS by performing standard and novel low-dose IGFGTs together with determination of spontaneous GH secretion. PATIENTS AND METHODS: Twenty-one (17 male) prepubertal children with ISS, mean age 8.3 years (4.5-12.2), mean height -3.48 SD (-5.40 to -1.79), mean peak GH to provocation with glucagon/clonidine 32.3 mU/l (14.1-66.0) were studied. Serum IGF-I and IGFBP-3 levels were measured during standard (GH 0.033 mg/kg/day x 4) and low (GH 0.011 mg/kg/day x 4) dose IGFGTs at 0, 12, 36 and 84 h. The low-dose IGFGT was performed in seven naive GH-deficient patients (4 male), mean age 8.5 years (range 4.1-11.1). Determination of spontaneous 24-h GH secretion was performed in the 21 ISS patients. RESULTS: Basal IGF-I and IGFBP-3 standard deviation scores (SDS) in ISS patients were -1.39 (-2.4-1.16) and -0.45 (-1.13-0.38), respectively, IGF-I being lower than IGFBP-3 (P < 0.0001). IGF-I increased in the standard IGFGT at 12 h (P < 0.005), 36 h (P < 0.001) and 84 h (P < 0.001); maximal increment 1.54 (-0.32-3.48), and in the low-dose test at 12 h (P < 0.005), 36 h (P < 0.001) and 84 h (P < 0.005); maximal increment 0.53 (0.08 to -1.23). IGFBP-3 SDS increased in the standard IGFGT at 36 h (P < 0.01) and 84 h (P < 0.001); maximal increment 0.72 (-0.44-1.96), and in the low-dose test at 84 h (P < 0.005); maximal increment 0.33 (-0.08-0.87). Five/19 patients with an IGF-I response > 2 x coefficient of variation (CV) of assay in the standard test failed to respond in the low-dose test, suggestive of mild GHI. In GH-deficient patients, IGF-I increased at each time point (P < 0.05) and IGFBP-3 at 36 h (P < 0.05). Mean GH secretion, expressed in SDS, compared with 66 normal stature controls was: basal GH -0.48 (-0.84-0.93), height of GH peaks compared with zero -0.36 (-1.26-1.51) (both P < 0.05), total GH secretion -0.76 (-1.22-0.42), total GH secretion above baseline -0.67 (-1.21-0.94) (both P < 0.01). CONCLUSIONS: In children with ISS, basal IGF-I and IGFBP-3 SDS values were below the mean, IGF-I showing a greater response in both IGFGTs. In the standard IGFGT, the IGF-I increase at 36 h was equal to that at 84 h. The low-dose IGFGT, in combination with the standard test, may identify patients with mild GHI.

Case-Control Studies↗
PubMed2004

Growth hormone (GH) insensitivity syndrome due to a GH receptor truncated after Box1, resulting in isolated failure of STAT 5 signal transduction.

Congenital GH insensitivity syndrome (GHIS) is usually the result of a mutation in the extracellular domain of the GH receptor (GHR). We report one of only a small number of mutations so far identified within the intracellular domain of the GHR. The probands are a 53-yr-old woman, height 114 cm (SD score, -8.7), peak GH 45 microg/liter during hypoglycemia, IGF-I 8.0 microg/liter [normal range (N) N 54-389], IGF binding protein-3 16 nmol/liter (N 61-254), GHBP 6.8% (N > 10); and her 57-yr-old brother, height 140 cm (SD score, -6), IGF-I 38.8 micro g/liter (N 54-290), IGF binding protein-3 30 nmol/liter (N 61-196). Both patients were homozygous for a 22-bp deletion in the DNA encoding the cytoplasmic domain of the GHR, resulting in a frameshift and premature stop codon. The resultant GHR is truncated at amino acid 449 (GHR1-449) after Box1, the Janus kinase 2 binding domain of the receptor. Functional studies in HEK293 and Chinese hamster ovary cells show GHR1-449 to have a cellular distribution similar to that of the wild-type GHR, judged by binding of iodinated GH, FACS analysis, and immunocytochemistry. Western blot analysis showed GH-induced phosphorylation of Janus kinase 2, signal transducer and activator of transcription (Stat)3, and Erk2 for both GHR1-449 and wild-type GHR. However, no Stat5 activity was detected in cells expressing GHR1-449, consistent with the fact that GHR1-449 contains no Stat5 binding site. In conclusion, we report two adult siblings with GHIS due to a mutation in the intracellular domain of GHR resulting in a selective loss of Stat5 signaling. Results are consistent with the hypothesis that the loss of signaling through the Stat5 pathway results in GHIS.

Amino Acid Sequence↗
PubMed2004

Comparison of continuation or cessation of growth hormone (GH) therapy on body composition and metabolic status in adolescents with severe GH deficiency at completion of linear growth.

Although GH replacement improves the features of GH deficiency (GHD) in adults, it has yet to be established whether cessation of GH at completion of childhood growth results in adverse consequences for the adolescent with GHD. Effects of continuation or cessation of GH on body composition, insulin sensitivity, and lipid levels were studied in 24 adolescents (13 males, 11 females, aged 17.0 +/- 0.3, yr, mean +/- se, puberty stage 4 or 5) in whom height velocity was less than 2 cm/yr. Provocative testing confirmed severe GHD [peak GH < 9 mU/liter (3 microg/liter)] in all cases and was followed by a lead-in period of 3 months during which the pediatric dose of GH continued unchanged. Baseline investigations were then performed using dual-energy x-ray absorptiometry (body composition), lipid measurements, and assessment of insulin sensitivity by both homeostasis model assessment and a short insulin tolerance test. Twelve patients remained on GH (0.35 U/kg.wk), and 12 patients ceased GH treatment. The groups were followed up in parallel with repeat observations made after 6 and 12 months. No endocrine differences were evident between the groups at baseline. GH cessation resulted in a reduction of serum IGF-I Z score [-1.62 +/- 0.29, baseline vs. -2.52 +/- 0.12, 6 months (P < 0.05) vs. -2.52 +/- 0.10, 12 months (P < 0.01)] but values remained unchanged in those continuing GH replacement. Lean body mass increased by 2.5 +/- 0.5 kg ( approximately 6%) over 12 months in those receiving GH but was unchanged after GH discontinuation. Cessation of GH resulted in increased insulin sensitivity [short insulin tolerance test, 153 +/- 22 micromol/liter.min, baseline vs. 187 +/- 20, 6 months (P < 0.05) vs. 204 +/- 14, 12 months (P = 0.05)], but no significant change was seen during 12 months of GH continuation. Lipid levels remained unaltered in both groups. Continuation of GH at completion of linear growth resulted in ongoing accrual of lean body mass (LBM), whereas skeletal muscle mass remained static after GH cessation in these adolescents with GHD. This divergence of gain in LBM is of potential importance because increases in LBM occur as a feature of healthy late adolescent development. GH is a major mediator of insulin sensitivity, independent of body composition in adolescents. Further studies are required to determine whether discontinuation of GH in the adolescent with severe GHD once linear growth is complete results in long-term irreversible adverse physical and metabolic consequences and to determine conclusively the benefits of continuing GH therapy.

Adolescent↗
PubMed2004

Pseudo-precocious puberty caused by a juvenile granulosa cell tumour secreting androstenedione, inhibin and insulin-like growth factor-I.

We report a female child who presented at age 3.92 years with a 2-year history of consonant pubertal development caused by a large right-sided ovarian juvenile granulosa cell tumour (JGCT). Although JGCTs causing pseudo-precocious puberty have been previously described, they remain rare and endocrine data are often incomplete. In this case the tumour was associated with raised serum oestradiol, androstenedione, inhibin and IGF-I. Histological changes were consistent with JGCT. Immunohistochemical studies revealed positive reactivity to MIC-2, inhibin, melan A, IGF-I and IGFBP-2.

Androstenedione↗
PubMed2003

The effect of cessation of growth hormone (GH) therapy on bone mineral accretion in GH-deficient adolescents at the completion of linear growth.

In many countries, treatment of childhood-onset GH deficiency (GHD) with GH ceases when linear growth is complete. Peak bone mass occurs several years after the completion of linear growth. Given that GH has important anabolic actions on bone, discontinuation of GH therapy at the completion of linear growth may have adverse consequences for the attainment of peak bone mass in adolescent GHD patients. In this United Kingdom multicenter study, 24 adolescents (13 males, mean age 17.0 +/- 1.4 yr, SD) with severe GHD were randomized to discontinue or continue GH (0.35 IU/kg x wk) at the completion of linear growth. Whole body bone mineral content (BMC) and lumbar spine bone mineral density were assessed by dual-energy x-ray absorptiometry at baseline and then at 6-month intervals for 1 yr. Markers of bone remodeling (serum bone-specific alkaline phosphatase and urinary deoxypyridinoline) were measured at the same time points. In patients who continued GH (GH+), median BMC increased by 3.8% (interquartile range, 2.6, 5.9, P < 0.001) at 6 months; and by 6.0% (3.7-9.1, P < 0.001) at 12 months. In patients who discontinued GH (GH-) median BMC was unchanged at 6 and 12 months (+1.9%, -0.4-4.2, P = 0.9; and +2.4%, 0.4-4.9, P = 0.5, respectively, median, interquartile range). The differences in median change in BMC between the two groups at 6 and 12 months was marginally significant (P = 0.085 and 0.074, respectively). Mean lumbar spine bone mineral density increased by 4.7 (95% confidence interval, 1.0, 8.2) at 12 months in patients continuing GH (P = 0.01), but the mean change was not statistically significant change in patients who discontinued GH [+2.7% (95% confidence interval, -0.8, +6.2)]. These preliminary data suggest that, in adolescent patients with severe GHD, discontinuation of GH at completion of growth may limit the attainment of peak bone mass in this patient group. This may predispose to clinically significant osteopenia in later adult life.

Adolescent↗
PubMed2003

Interleukin-1beta (IL-1beta) and IL-6 modulate insulin-like growth factor-binding protein (IGFBP) secretion in colon cancer epithelial (Caco-2) cells.

Chronic inflammation is characterised by modifications in cytokine concentrations, whereas growth is mainly dependent on the GH-IGF axis. IGF-I bioavailability is modulated by a family of IGF-binding proteins (IGFBPs). The aim of the present study was to evaluate the interactions among interleukin-1beta (IL-1beta), IL-6 and IGFBP secretion by intestinal cells to assess whether cytokines modulate IGFBP secretion, and in turn IGF-I and IGF-II bioavailability. The human colon carcinoma derived cell line Caco-2 was used as an in vitro model for its capacity to differentiate spontaneously. Experiments were carried out on day 4 (undifferentiated state) and day 14 (differentiated state) after plating. Carcinoembryonic antigen (CEA) was used as a marker of differentiation and increased in the conditioned media (CM) from days 4 to 14 (0.2+/-0.01 ng/ml per 10(5) cells vs 3.3+/-0.2 ng/ml per 10(5) cells, P<0.05). IGFBP-2 and IGFBP-4 secretion decreased concomitantly. Cells were stimulated with IL-1beta and IL-6 at 1, 10 and 50 ng/ml, and with IL-1beta and IL-6 in combination at the same dose of 1 and 10 ng/ml. IGF-I at 50 ng/ml was used as a control. Caco-2 cells expressed and secreted mainly IGFBP-2 and IGFBP-4 into the CM. On day 4, IL-1beta (1 ng/ml) and IL-6 (10 and 50 ng/ml) reduced IGFBP-2 by 29+/-8%, and by 32+/-9 and 38+/-8% respectively (P<0.05). IGFBP-4 was also reduced by IL-1beta at 1 and 50 ng/ml (-14+/-4% and -46+/-11% vs serum free medium (SFM) respectively, P<0.05), and IL-6 at 50 ng/ml (-46+/-15%, P<0.05). Both IGFBP-2 and IGFBP-4 were reduced by IL-1beta and IL-6 in combination at 1 and 10 ng/ml (P<0.05). On day 14, IGFBP-2 band intensity was reduced at 10 ng/ml of IL-1beta (-22+/-15% vs SFM, P<0.05) and at 50 ng/ml of both cytokines (-33%+/-8% and -13%+/-13% vs baseline respectively, P<0.05). IGFBP-4 band intensity decreased with 10 and 50 ng/ml of IL-1beta (-35+/-11% and -46+/-15% vs SFM respectively) and IL-6 (-36%+/-10% and -46+/-15% vs SFM respectively). IL-1beta and IL-6 in combination at 1 and 10 ng/ml reduced both IGFBP-2 and IGFBP-4.In conclusion, IGFBP-2 and IGFBP-4 secretion in CM decreased with Caco-2 cell differentiation. IGFBP-2 and IGFBP-4 were significantly decreased by IL-1beta and IL-6 treatment in both the undifferentiated and differentiated state. Furthermore, these cytokines increased cell proliferation whereas total protein content was significantly reduced only at the higher concentrations of IL-6 and IL-1beta. These findings suggest that interleukins modulate the IGF-IGFBP system in Caco-2 cells in vitro.

Caco-2 Cells↗
PubMed2002

Growth hormone replacement does not increase serum prostate-specific antigen in hypopituitary men over 50 years.

OBJECTIVE: Epidemiological studies have shown an increased risk for prostate carcinoma in men with serum IGF-I in the upper part of the age-related reference range. Recombinant human GH (rhGH) is widely used in patients with GH deficiency, usually raising the serum IGF-I levels into the normal range: safety surveillance is therefore mandatory, with particular regard to neoplasia. The aim was to examine whether rhGH replacement in hypopituitary adults is associated with changes in serum prostate-specific antigen (PSA) as a surrogate marker of changes in prostatic growth. DESIGN AND METHODS: A prospective longitudinal study was used with a median follow-up of 22 (range 2.5-32) months, in which 41 men aged over 50 years with adult onset hypopituitarism and GH deficiency during rhGH replacement were examined. Serum PSA and IGF-I were measured at baseline and at latest follow-up. RESULTS: Mean serum PSA remained unchanged during rhGH replacement, with a median follow-up of 2 years. No correlation was found between the individual changes in serum IGF-I and changes in serum PSA. CONCLUSIONS: These data are reassuring thus far regarding the safety of GH replacement in relation to the prostate in this patient group.

Aged↗
PubMed2001

Is there a medical need to explore the clinical use of insulin-like growth factor I?

Cloning of the insulin-like growth factor I (IGF-I) gene led to the development in 1987 of recombinant IGF-I available for clinical use. Trials were started targeting endocrine, metabolic and neurological disorders, and beneficial results have been demonstrated in IGF-I deficiency states caused by IGF-I gene deletion and growth hormone (GH) receptor deficiency, type 1 and type 2 diabetes mellitus, and severe insulin resistance syndromes. Results of equivocal benefit have also been reported in osteoporosis and amyotrophic lateral sclerosis. Recent encouraging data using the IGF-I-IGF-binding protein 3 (IGFBP-3) complex in diabetes mellitus suggest that this preparation may eventually replace recombinant free IGF-I. The lack of an established therapeutic indication for IGF-I has resulted in its supplies being severely limited. It will probably be decided during the next decade whether use of IGF-I or the IGF-I-IGFBP-3 complex becomes firmly established as an accepted endocrine therapy.

Clinical Trials as Topic↗
PubMed2001

Increased levels of insulin-like growth factor binding protein-2 in sera and tumours from patients with colonic neoplasia with and without acromegaly.

OBJECTIVE: Patients with acromegaly are at increased risk of developing colorectal carcinoma and premalignant tubulovillous adenoma. The pathogenesis of these neoplasms could involve a stimulatory effect of serum growth factors on colonic epithelial cell proliferation. The aim of this study was to evaluate changes in (1) serum IGF-I, IGF-II, IGFBP-3 and IGFBP-2 and (2) changes in local expression of IGFBPs and p53 in colonic epithelium in patients with colonic neoplasia with and without acromegaly. DESIGN: A cross-sectional retrospective study was performed. Fasting serum samples were obtained at the time of colonoscopy for patients with acromegaly and at the time of surgery for patients with colonic neoplasia without acromegaly. MEASUREMENTS: Serum IGF-I, IGF-II, IGFBP-2 and IGFBP-3 were measured using specific immunoassays. Tissue expression of IGFBP-2, IGFBP-3 and p53 status were determined by immunohistochemistry. PATIENTS: Group 1: 26 age- and sex-matched control subjects (range 40-69 years); group 2: 18 patients with acromegaly without colonic neoplasia (range 39-68 years); group 3: 18 patients with acromegaly and colonic neoplasia (range 41-74 years, 11 = adenoma, seven = carcinoma); group 4: 19 patients with colonic neoplasia without endocrine disease (range 43-91 years, four = adenoma, 15 = carcinoma). Immunohistochemical staining of colonic biopsies was performed for IGFBP-2, IGFBP-3 and p53 in groups 3 and 4. RESULTS: Mean serum IGF-I and IGFBP-3 levels were significantly elevated in group 2 (371 +/- 131 microg/l and 6.5 +/- 1.8 mg/l, respectively) and group 3 (379 +/- 174 microg/l and 5.8 +/- 1.6 mg/l, respectively), and significantly reduced in group 4 (103 +/- 36 microg/l and 2.4 +/- 1 mg/l) compared to controls (165 +/- 40 microg/l and 4.7 +/- 1 mg/l; P < 0.0001, P < 0.001, respectively). However, median serum IGFBP-2 levels were significantly elevated in group 3 (P < 0.01) and group 4 (P < 0.0001). Immunostaining for IGFBP-2 showed strong areas of immunoreactivity in the cytoplasm of malignant colonic epithelium compared to benign epithelium. IGFBP-3 immunostaining showed strong areas of immunoreactivity in the cytoplasm and in the nucleus of malignant and benign colonic epithelium compared to the normal epithelium. Nuclear staining for p53 was observed in three patients from group 3 (two carcinoma, one adenoma) and four patients from group 4 (all carcinoma). CONCLUSION: Our results describe changes in IGFBP-2 expression in colonic neoplasia in patients with and without acromegaly, which suggest that this binding protein may regulate local bioavailability of IGF, which in turn could modulate colonic cell proliferation and/or differentiation.

Acromegaly↗
PubMed2001

Insulin-like growth factor -I deficiency.

The insulin-like growth factor (IGF) system composed of two ligands, their receptors and regulatory proteins (acid-labile subunit and IGF-binding proteins) plays a central role in the regulation of growth and development in mammals. In addition to its key role in the stimulation of cellular proliferation and growth, IGF-I has important effects on carbohydrate, protein and bone metabolism. The molecular biology and physiology of the IGF system are complex, resulting in many potential mechanisms of IGF deficiency. Briefly, IGF-I deficiency may result from a primary defect in the IGF-I gene, its promoters, or may be secondary to a defect outside the gene itself. It may also result as a consequence of growth hormone (GH) deficiency, GH receptor/post-receptor abnormalities or abnormalities of the IGF-I receptor. The purpose of this presentation is to review the different types of IGF-I deficiency using the well-characterized clinical conditions with its associated biochemical and molecular defects. The clinical consequences in terms of phenotype-genotype, linear growth and body composition in patients with primary and secondary IGF deficiency will be presented, together with results from recombinant human (rh)IGF-I replacement therapy. Finally, as primary IGF-I deficiency is associated with insulin resistance, some of the metabolic actions of IGF-I will be briefly discussed.

Humans↗
PubMed2001

Growth hormone insensitivity: pathophysiology, diagnosis, clinical variation and future perspectives.

The study of genetic growth hormone (GH) insensitivity is an evolving field. GH insensitivity syndrome (GHIS), otherwise known as Laron syndrome, is a heterogeneous disorder. Biochemical features consist of severe insulin-like growth factor I (IGF-I) and IGF-binding protein 3 (IGFBP-3) deficiency and elevated GH secretion. In a heterogeneous 'European' cohort of GHIS patients, features varied from classical to moderate abnormalities of phenotype and endocrine disturbance. A study of facial features within this series showed that a mild subgroup existed with normal facies, mild short stature and moderate biochemical abnormalities. Overlap with idiopathic short stature (ISS) exists, with heterozygous mutations of the GH receptor demonstrated to cause impaired growth. This 'partial' GHIS has not yet been defined endocrinologically. GH sensitivity, measured by IGF-I and IGFBP-3 responses in the IGF-I generation test, may reveal abnormalities in ISS, although it is likely that the dose of recombinant human GH and frequency of sampling in the test need to be modified.

Body Height↗
PubMed2000

Assessment of growth hormone status in acromegaly: what biochemical markers to measure and how?

Various studies have evaluated the usefulness of measuring insulin-like growth factor I (IGF-I) and IGF-binding proteins, compared with growth hormone (GH), in the diagnosis and follow-up of patients with acromegaly. The clinical use of recently developed, highly sensitive GH assays has improved our understanding of the secretion of GH at very low concentrations. Studies examining the GH nadir after oral glucose administration in healthy adults suggest that GH values should be suppressed to no more than 0.14 microg/l after oral glucose administration. The highly sensitive GH assays are now being used in the diagnosis of patients with acromegaly and in post-treatment follow-up. In addition, the use of IGF-I immunoassays has confirmed that serum IGF-I level is a reliable and useful biochemical marker for determining GH excess. The widespread use of highly sensitive, carefully validated assays offers accurate and reproducible biochemical information that will help in the overall clinical management of patients with acromegaly, including the monitoring of disease remission, disease cure and treatment titration regimen, as well as the early recognition of patients with residual disease.

Acromegaly↗
PubMed2000

Analysis of the intracellular signalling domain of the human growth hormone receptor in children with idiopathic short stature.

OBJECTIVE: To investigate the hypothesis that intracellular, dominant-negative mutations of the growth hormone receptor (GHR) exist in children with idiopathic short stature (ISS) and partial growth hormone insensitivity (GHI). SUBJECTS: We studied 31 children aged 4.55-13.14 years with ISS (height </= -1.8 standard deviation scores, UK standards 1990). GH provocation tests (glucagon 15 microg kg-1 i.m.) excluded GH deficiency in all subjects. Serum IGF-I levels were below the 50th centile for age in all subjects and below the 10th centile in 64.5% of cases. GH binding protein levels were normal in the 24 subjects in whom it was measured (mean 25.2%; range 10-42.6%). METHODS: Exons 9 and 10 of the GHR were amplified by PCR from leucocyte-derived DNA. Samples were directly sequenced on the ABI 377 DNA analyser using the - 21 M13 dye primer cycle sequencing protocol for optimum heterozygote detection. RESULTS: No abnormalities were detected in exon 9 which encodes the proline-rich box 1 motif. In exon 10 two sequence variants were found; a heterozygous, single base alteration (TCT to TCC) in codon 325 which does not change the amino acid sequence in one patient, and the L526I variant in 24 subjects. L526I is a conservative amino acid change and had an allele frequency of 0.53 in our patients, which is similar to that reported in a control population. CONCLUSIONS: The apparent partial growth hormone insensitivity in this group of idiopathic short-stature subjects is not related to heterozygous, dominant-negative variants of the intracellular signalling domain of the GHR. Hence it is likely that other genetic and environmental factors may be involved.

Adolescent↗