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Biomedical subjects

C Camacho-Hübner

Publications and source records attributed to C Camacho-Hübner.

At least 19 recordsLinked to original sources

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↗

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↗

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↗

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↗

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↗

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↗

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↗

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↗

Effects of insulin-like growth factor I (IGF-I) therapy on body composition and insulin resistance in IGF-I gene deletion.

We have recently reported a patient with a homozygous partial deletion of the insulin-like growth factor-I (IGF-I) gene, resulting in IGF-I deficiency, insulin resistance, and short stature. Recombinant human IGF-I (rhIGF-I) therapy has been shown to improve insulin sensitivity (Si) and growth in other causes of IGF-I deficiency. We now report results of 1 yr of rhIGF-I therapy on body composition, bone mineral density (BMD), insulin sensitivity, and linear growth in this patient. rhIGF-I therapy was initiated at age 16.07 yr (bone age, 14.2 yr), at a starting dose of 40 microg/kg daily, increasing after 3 months to 80 microg/kg daily. Body composition, BMD, markers of bone mineralization, and auxological parameters (height, weight) were measured at 0, 6, and 12 months after start of therapy. Si, acute insulin response to glucose, and glucose effectiveness were determined at baseline, 3 months, and 12 months into therapy. On IGF-I therapy, body mass index increased from 17 kg/m2 to 18.6 kg/m2. Body composition studies (dual-energy x-ray absorbtiometry) revealed an initial decrease in total body fat, from 19.9% at baseline to 15.1% at 6 months; but by 12 months of therapy, this had reversed, with an increase to 21.8%. Si, calculated using Bergman's minimal model, was substantially reduced at baseline at 1.45 x 10-4 min-1 (microU/mL) [normal value, 5.1 x 10-4 min 1 (lean adult male)]. rhIGF-I therapy resulted in a dose-related improvement of Si into the normal range (NR) (rhIGF-I dose: 40 microg/kg x day, Si = 2.06 x 10-4 min-l; rhIGF-I dose: 80 microg/kg x day, Si = 4.39 x 10-4 min-1). Baseline reduction in Si was accompanied by elevated acute insulin response to glucose, which also fell in a dose-dependent manner. Baseline BMD was severely reduced when compared with age-matched controls (-4.88 SD); however, calculation of bone mineral apparent density indicated that the true reduction in BMD was minimal. rhIGF-I therapy increased BMD by 17% and bone mineral apparent density by 7%, indicating that IGF-I has a greater effect on bone growth than bone mineralization. Bone turnover markers also increased on rhIGF-I; mean serum osteocalcin: 8.3 ng/mL pretreatment, 21.7 ng/mL after 6 months of rhIGF-I (NR for adult male, 3.4-9.1 ng/mL); mean bone specific alkaline phosphatase: 36.5 U/L pretreatment, 82.2 U/L after 6 months of therapy (NR for adult male, 15-41). Height velocity increased from 3.8 cm/yr pretreatment to 7.3 cm/yr on 80 microg/kg.day of rhIGF-I. In this patient with severe insulin resistance, therapy with rhIGF-I resulted in beneficial effects on Si, body composition, bone size, and linear growth. These results have implications for IGF-I therapy in a variety insulin resistant states.

Absorptiometry, Photon↗

IGF-I levels rise and GH responses to GHRH decrease during long-term prednisone treatment in man.

Glucocorticoid excess is associated with a blunted GH response to GHRH. IGF-I levels in hypercortisolism are controversial and have been reported as low, normal or high. The aim of this study was to evaluate longitudinally time-dependent changes in the GH response to GHRH, IGF-I, IGFBP-3 and albumin values in patients during corticotherapy. Six patients received GHRH before and after one week and one month of prednisone administration (20-60 mg/d, orally). IGF-I, IGFBP-3 and albumin were determined in each test, at time 0. Ten normal controls were also evaluated in one occasion. There were no differences in basal GH values, GH response to GHRH, IGF-I and IGFBP-3 levels between controls and patients before starting corticotherapy. Albumin (g/l; mean+/-SE) values were lower in patients before treatment (31+/-4) than in controls (43+/-1). After one week of prednisone administration there was a significant decrease in peak GH (microg/l) levels (before: 18.8+/-7.4; 1 week: 5.0+/-1.3), which was maintained after one month (8.1+/-3.5). IGF-I (microg/l) levels increased significantly, from 145+/-23 to 205+/-52 after one week of therapy, reaching levels of 262+/-32 after one month. IGFBP-3 (mg/l) values did not increase significantly (before: 2.1+/-0.2; 1 week: 2.5+/-0.3; 1 month: 2.8+/-0.2). Albumin levels showed a significant rise both after one week (36+/-4) and one month (42+/-3) of corticotherapy. In summary, we observed a marked decrease in the GH response to GHRH after one week and one month of prednisone administration associated with an increase in circulating IGF-I and albumin values. The physiological implications of these findings are still uncertain. It is possible that glucocorticoids increase hepatic IGF-I and albumin synthesis, although other mechanisms may have a role.

Adult↗

Insulin-like growth factor-I deficiency caused by a partial deletion of the IGF-I gene: effects of rhIGF-I therapy.

Insulin-like growth factor-I (IGF-I) is one of the most important regulator of growth. IGF-I deficiency is associated with prenatal and post-natal growth failure and may arise primarily as a result of GH receptor/post-receptor abnormalities or defects in the synthesis and transport of IGF-I. We have previously reported a 17.2-year-old boy with severe growth retardation and undetectable serum levels of IGF-I caused by a partial deletion of the IGF-I gene. This short review will concentrate on results of a recent study which examined the effects of rhIGF-I therapy on the GH-IGF system of this patient. Similar to healthy individuals, this patient had normal IGFBP-3 but elevated ALS levels. IGF-I treatment has improved linear growth and insulin sensitivity in this patient by restoring IGF-I levels and by normalizing circulating GH, IGFBPs and insulin levels.

Adolescent↗

Correlation between cortisol and insulin-like growth factor-binding proteins (IGFBPs) under physiological conditions in children.

OBJECTIVE: A positive correlation between 24-h spontaneous growth hormone (GH) and cortisol secretion was previously reported in children. This observation prompted us to examine the relationship between physiological diurnal cortisol variation and the levels of insulin-like growth factors (IGFs) and IGF-binding proteins (IGFBPs) under physiological conditions. DESIGN AND PATIENTS: Starting at 0800 h, blood was sampled every 20 minutes over 24 h for measurement of GH and cortisol concentration in nine non-GH- deficient boys as part of a protocol for the investigation of short stature. MEASUREMENTS: IGFBP-1 and insulin were measured in samples drawn every 4 h over the 24-h period while IGF-I, IGF-II, IGFBP-2 and IGFBP-3 were determined in samples collected at the end of the study. RESULTS: No correlation was observed between IGF-I or IGF-II and mean cortisol levels. IGFBP-1 concentrations showed a marked circadian variation that was superimposed on the circadian rhythm for cortisol while a significant positive correlation was found for single point measurements between IGFBP-1 concentrations and cortisol levels measured in the same sample (r = 0.53) or at the preceding 20 minutes (r = 0.43), 40 minutes (r = 0.47) and 2 h (r = 0.38), suggesting an interplay between cortisol and IGFBP-1. A negative correlation (r = - 0.54) was found between IGFBP-1 and insulin levels determined in the same sample. A negative correlation (r = - 0.93) was also found between IGFBP-2 levels and mean cortisol concentrations during the preceding 12 h. No correlation was observed between plasma IGFBP-3 measured by IRMA and mean cortisol levels. CONCLUSION: Our data indicate a clear correlation between cortisol and IGFBP-1 and IGFBP-2 levels. Thus, the interplay of spontaneous GH and cortisol secretion in children may involve changes in IGFBP-1 and IGFBP-2 levels.

Adolescent↗

Serum insulin-like growth factor (IGF)-I concentrations are reduced by short-term dietary restriction and restored by refeeding in domestic cats (Felis catus).

Nutritional modulation of insulin-like growth factors (IGF) and their binding proteins (IGFBP) is well established. The effect of nutritional restriction on the serum IGF/IGFBP system of adult cats was investigated to evaluate serum IGF-I as a biochemical marker of nutritional status. Assays for measuring feline serum IGF and IGFBP were validated and normal ranges established in a study population of 46 healthy nonobese adult cats. Serum concentrations of IGF-I and IGF-II correlated significantly with body weight (r = 0.75, P < 0. 0001 and r = 0.34, P < 0.03, respectively). Serum IGFBP profiles were similar to other species, including humans, dogs and guinea pigs. IGFBP-3 was the predominant binding protein reflecting IGF-I concentrations and body size. Serum IGFBP-2 concentrations were high relative to the normal human serum pool (NHS) control. Food withdrawal for 18 h followed by refeeding did not alter circulating IGF or IGFBP concentrations, including IGFBP-1, in nine cats. Short-term dietary restriction of nine adult cats to supply initially 56% (56%M) and then 42.5% (42.5%M) of calculated maintenance energy requirements for 14 d resulted in a significant weight loss (P < 0.01). However, serum IGF-I concentrations fell significantly (-51%, P < 0.01) only with 42.5%M restriction. Serum IGF-II, IGFBP, insulin and albumin concentrations were not altered during the study. We conclude that nutrition does modulate the adult feline IGF/IGFBP system, but to a lesser extent than in other species. Further evaluation is required before serum IGF-I can be used for the assessment of nutritional status in adult cats.

Animals↗

Growth in Crohn's disease.

Abnormal linear growth is frequent in children and adolescents with Crohn's disease. The typical pattern is of growth retardation associated with delayed skeletal maturation. Puberty is also frequently delayed. Over 50% of patients may have a subnormal height velocity, and approximately 25% will have short stature. The endocrine status is characterized by normal growth hormone secretion and a slightly subnormal serum level of insulin-like growth factor I, which is related to nutritional status. Principal therapeutic options are intestinal resection for localized disease, and enteral nutrition--using a polymeric diet--for more widespread disease, particularly involving the small intestine. Growth responses to both modalities are often excellent and produce considerable psychological benefit. Optimum therapy is achieved by close collaboration between gastroenterologists and endocrinologists, and by the use of auxological methods to document pre- and post-therapeutic management.

Adolescent↗

Effects of recombinant human insulin-like growth factor I (IGF-I) therapy on the growth hormone-IGF system of a patient with a partial IGF-I gene deletion.

We have previously reported a 17.2-yr-old boy with severe growth retardation and undetectable serum levels of insulin-like growth factor I (IGF-I) due to a partial deletion of the IGF-I gene. The aim of this study was to investigate the effects of recombinant human IGF-I (rhIGF-I) therapy on the GH-IGF system of this patient to gain further insights into its growth-promoting and metabolic actions. To assess the changes in GH, IGFs, IGF-binding proteins (IGFBPs), acid-labile subunit (ALS), and insulin levels, blood samples were obtained before therapy and during the first year of treatment. Hormones were analyzed by specific RIAs. Overnight GH profiles were performed before and at 1, 6, and 12 months of therapy. Fasting ALS, IGF-II, IGFBP-3, IGFBP-2, IGFBP-1, and insulin levels before rhIGF-I treatment were 46.3 mg/L, 1044 microg/L, 5.8 mg/L, 73 ng/mL, 4.7 ng/mL, and 27.3 mU/L, respectively. IGF-II, ALS, and insulin levels were elevated, whereas IGFBP-1 and IGFBP-2 levels were decreased compared to reference values. Twenty-four hours after a single s.c. injection of rhIGF-I (40 microg/kg), the concentrations were 46 mg/L, 888 microg/L, 6.9 mg/L, 112 ng/mL, 5.0 ng/mL, and 21.0 mU/L, respectively. After a single s.c. injection of rhIGF-I of 40 or 80 microg/kg x day and modelling the data using a two-compartment model, the half-lives of elimination were 15.7 and 14.3 h, with a maximum increase in IGF-I levels to 341 and 794 microg/L around 7 h, respectively. An increase in IGFBP-3 levels was observed with both doses of rhIGF-I, with a peak values of 9 mg/L. GH profiles showed a decrease in peak amplitude from 342 to 84 mU/L at 1 month, to 67 mU/L at 6 months, and to 40 mU/L at 1 yr of therapy, with no significant changes in peak number. A significant increase in IGFBP-1 levels was observed during treatment with 80 microg/kg x day IGF-I, reflecting the inhibitory effect of rhIGF-I on insulin secretion. The clinical response to rhIGF-I therapy was an increased height velocity from 3.8 cm/yr before treatment to 6.6 cm/yr. Increased lean body mass correlated with changes in the doses of rhIGF-I and, in turn, with the biochemical changes in the GH-IGF axis. Similar to healthy individuals, this patient had normal IGFBP-3 and ALS levels, which are the major regulators of the pharmacokinetics of rhIGF-I. In summary, rhIGF-I treatment has improved linear growth and insulin sensitivity in this patient by restoring IGF-I levels and by normalizing circulating GH, IGFBP, and insulin levels.

Adolescent↗