The single-point insulin sensitivity estimator (SPISE) index is a strong predictor of abnormal glucose metabolism in overweight/obese children: a long-term follow-up study.

PURPOSE: To investigate the relationship between the single-point insulin sensitivity estimator (SPISE) index, an insulin sensitivity indicator validated in adolescents and adults, and metabolic profile in overweight/obese children, and to evaluate whether basal SPISE is predictive of impaired glucose regulation (IGR) development later in life. METHODS: The SPISE index (= 600 × HDL0.185/Triglycerides0.2 × BMI1.338) was calculated in 909 overweight/obese children undergoing metabolic evaluations at University of Cagliari, Italy, and in 99 normal-weight, age-, sex-comparable children, selected as a reference group, together with other insulin-derived indicators of insulin sensitivity/resistance. 200 overweight/obese children were followed-up for 6.5 [3.5-10] years, data were used for longitudinal retrospective investigations. RESULTS: At baseline, 96/909 (11%) overweight/obese children had IGR; in this subgroup, SPISE was significantly lower than in normo-glycaemic youths (6.3 ± 1.7 vs. 7 ± 1.6, p < 0.001). The SPISE index correlated positively with the insulin sensitivity index (ISI) and the disposition index (DI), negatively with age, blood pressure, HOMA-IR, basal and 120 min blood glucose and insulin (all p values < 0.001). A correlation between SPISE, HOMA-IR and ISI was also reported in normal-weight children. At the 6.5-year follow-up, lower basal SPISE-but not ISI or HOMA-IR-was an independent predictor of IGR development (OR = 3.89(1.65-9.13), p = 0.002; AUROC: 0.82(0.72-0.92), p < 0.001). CONCLUSION: In children, low SPISE index is significantly associated with metabolic abnormalities and predicts the development of IGR in life.

Adherence to growth hormone (GH) therapy in naïve to treatment GH-deficient children: data of the Italian Cohort from the Easypod Connect Observational Study (ECOS).

BACKGROUND: With the use of non-objective measurement, adherence to growth hormone (GH) therapy has been reported suboptimal in a large proportion of patients, and poor adherence has been shown to affect short-term growth response in patients receiving GH treatment. OBJECTIVE: The Easypod™ electronic device allows objective measurement of adherence. In this study, we report 3-year prospective adherence data of the Italian cohort of naïve GH deficient (GHD) children extrapolated from the Easypod Connect Observational Study (ECOS) database. PATIENTS AND METHODS: Seventy-three GHD children naïve to GH treatment were included in the analysis. 22 Italian centers participated in the study. RESULTS: Mean adherence rate was consistently above 85% across the 3-year observation period. Particularly, mean adherence was 88.5%, 86.6%, and 85.7% after 1, 2 and 3 years, respectively. Mean (± SD) height-SDS increase after the first year was 0.41 (± 0.38). CONCLUSIONS: The majority of naïve GHD children starting GH treatment with Easypod maintained an adherence rate > 85% up to 3 years. Easypod is a useful tool to follow-up patients' adherence allowing timely intervention to improve optimal treatment for these patients.

A genetic epidemiology study of congenital adrenal hyperplasia in Italy.

Congenital adrenal hyperplasia due to 21-hydroxylase deficiency (21OHD-CAH) is an autosomal recessive disorder affecting steroidogenesis, due to mutations in CYP21A2 (6p21.3). 21OHD-CAH neonatal screening is based on 17-hydroxyprogesterone (17OHP) serum levels, showing high type I error rate and low sensitivity to mild CAH forms. Here, we used an epidemiological approach, which estimates the allelic frequency (q) of an autosomal recessive disorder using the proportion of homozygous patients, the mutational spectrum and the inbreeding coefficient in a sample of affected individuals. We applied this approach to 2 independent Italian cohorts of patients with both clinical and molecular diagnosis of 21OHD-CAH from mainland Italy (N = 240) and Sardinia (N = 53). We inferred q estimates of 2.87% and 1.83%, corresponding to a prevalence of 1/1214 and 1/2986, respectively. CYP21A2 mutational spectra were quite discrepant between the 2 cohorts, with V281L representing 74% of all the mutations detected in Sardinia vs 37% in mainland Italy. These findings provide an updated fine-grained picture of 21OHD-CAH genetic epidemiology in Italy and suggest the need for a screening approach suitable to the detection of the largest number of clinically significant forms of CAH.

A new index to simplify the screening of hypertension in overweight or obese youth.

BACKGROUND AND AIMS: Hypertension (HTH) is a frequent complication in pediatric obesity. To simplify the screening of HTH in overweight/obese (Ow/Ob) youth, we compared the performance of a new index (High Blood Pressure index, HBPi) with respect to the standard criteria of the IV Report [systolic BP (SBP) and/or diastolic BP (DBP) ≥95th percentile for age, gender and height]. We also compared the performance of HBPi with other simplified indices such as the BP/height ratio and the absolute height-specific BP thresholds. Ten pediatrics' outpatient centers participating in the "CARdiometabolic risk factors in ITALY study" provided medical records of 4225 Ow/Ob children and adolescents (age 6-16 years). METHODS AND RESULTS: Centers were divided into two groups: training set (TS) (n = 2204 participants) and validation set (VS) (n = 2021 participants). The simplified HBPi (mmHg) was: (SBP/2 + DBP/10) - age + (1 × female gender). In the TS, a HBPi value ≥57 mmHg in both children and adolescents had high sensitivity (0.89), specificity (0.97), positive (0.89) and negative (0.97) predictive values in classifying youth at high risk of HTN compared with the IV Report. In the VS, the HBPi showed a better performance than high levels of BP/height ratio and height-specific BP thresholds in classifying individuals at risk of HTN: area under curves 0.95 (0.93-0.96), 0.80 (0.78-0.82), 0.76 (0.74-0.79), respectively; specificities 0.95 (0.94-0.96), 0.69 (0.67-0.72), 0.60 (0.57-0.62), respectively. CONCLUSIONS: HBPi, combining SBP and DBP, gender and age, may help pediatricians to implement HTN screening in Ow/Ob youth.

Impaired fasting glucose and impaired glucose tolerance in children and adolescents with overweight/obesity.

OBJECTIVE: To investigate in a large sample of overweight/obese (OW/OB) children and adolescents the prevalence of prediabetic phenotypes such as impaired fasting glucose (IFG) and impaired glucose tolerance (IGT), and to assess their association with cardiometabolic risk (CMR) factors including hepatic steatosis (HS). METHODS: Population data were obtained from the CARdiometabolic risk factors in children and adolescents in ITALY study. Between 2003 and 2013, 3088 youths (972 children and 2116 adolescents) received oral glucose tolerance test (OGTT) and were included in the study. In 798 individuals, abdominal ultrasound for identification of HS was available. RESULTS: The prevalence of IFG (3.2 vs. 3.3%) and IGT (4.6 vs. 5.0%) was similar between children and adolescents. Children with isolated IGT had a 2-11 fold increased risk of high LDL-C, non-HDL-C, Tg/HDL-C ratio, and low insulin sensitivity, when compared to those with normal glucose tolerance (NGT). No significant association of IFG with any CMR factor was found in children. Among adolescents, IGT subjects, and to a lesser extent those with IFG, showed a worse CMR profile compared to NGT subgroup. In the overall sample, IGT phenotype showed a twofold increased risk of HS compared to NGT subgroup. CONCLUSIONS: Our study shows an unexpected similar prevalence of IFG and IGT between children and adolescents with overweight/obesity. The IGT phenotype was associated with a worse CMR profile in both children and adolescents. Phenotyping prediabetes conditions by OGTT should be done as part of prediction and prevention of cardiometabolic diseases in OW/OB youth since early childhood.

The vitamin D receptor (VDR) gene rs11568820 variant is associated with type 2 diabetes and impaired insulin secretion in Italian adult subjects, and associates with increased cardio-metabolic risk in children.

BACKGROUND AND AIMS: 1α,25-dihydroxyvitamin-D3, the biologically active vitamin D, plays a central role in several metabolic pathways through the binding to the vitamin D receptor (VDR). VDR has been shown to be involved in cardiovascular diseases, cancer, autoimmunity and type 2 diabetes mellitus (T2DM). Several polymorphisms in the VDR gene have been described. Among these, the rs11568820 G-to-A nucleotide substitution was found to be functional, modulating the transcription of the VDR gene. Objective of this study was to perform an association study between rs11568820 polymorphism and T2DM in a cohort of Italian adults with T2DM and in non-diabetic controls. To add further insight into the role of VDR gene we explored whether this association begins early in life in overweight/obese children, or becomes manifest only in adulthood. METHODS AND RESULTS: As many as 1788 adults and 878 children were genotyped for the rs11568820 polymorphism. All participants underwent oral glucose tolerance tests (OGTT), with measurement of glucose and insulin levels. Indices of insulin-resistance and secretion were also calculated. The AA genotype was significantly more frequent in adults with T2DM compared to controls (7.5% vs. 4.6%, P = 0.037), and conferred a higher risk of T2DM (ORHom = 1.69C.I. = [1.13-2.53], P = 0.011). In the adult cohort, rs11568820 was also associated with reduced indices of ß-cell insulin secretion. In children, the AA genotype was associated with 2 h high-normal glucose, a marker of cardio-metabolic risk. CONCLUSIONS: Our study demonstrates for the first time that VDR gene AA carriers have higher risk of T2DM and impaired insulin secretion. In children, the association between AA homozygous and high-normal 2h glucose suggests that mild alterations associated with this genotype may appear early in life.

Efficacy and safety of growth hormone treatment in children with short stature: the Italian cohort of the GeNeSIS clinical study.

PURPOSE: We examined auxological changes in growth hormone (GH)-treated children in Italy using data from the Italian cohort of the multinational observational Genetics and Neuroendocrinology of Short Stature International Study (GeNeSIS) of pediatric patients requiring GH treatment. METHODS: We studied 711 children (median baseline age 9.6 years). Diagnosis associated with short stature was as determined by the investigator. Height standard deviation score (SDS) was evaluated yearly until final or near-final height (n = 78). Adverse events were assessed in all GH-treated patients. RESULTS: The diagnosis resulting in GH treatment was GH deficiency (GHD) in 85.5 % of patients, followed by Turner syndrome (TS 6.6 %). Median starting GH dose was higher in patients with TS (0.30 mg/kg/week) than patients with GHD (0.23 mg/kg/week). Median (interquartile range) GH treatment duration was 2.6 (0.6-3.7) years. Mean (95 % confidence interval) final height SDS gain was 2.00 (1.27-2.73) for patients with organic GHD (n = 18) and 1.19 (0.97-1.40) for patients with idiopathic GHD (n = 41), but lower for patients with TS, 0.37 (-0.03 to 0.77, n = 13). Final height SDS was >-2 for 94 % of organic GHD, 88 % of idiopathic GHD and 62 % of TS patients. Mean age at GH start was lower for organic GHD patients, and treatment duration was longer than for other groups, resulting in greater mean final height gain. GH-related adverse events occurred mainly in patients diagnosed with idiopathic GHD. CONCLUSIONS: Data from the Italian cohort of GeNeSIS showed auxological changes and safety of GH therapy consistent with results from international surveillance databases.

Adherence in children with growth hormone deficiency treated with r-hGH and the easypod™ device.

PURPOSE: Poor adherence to recombinant human growth hormone (r-hGH) therapy is associated with reduced growth velocity in children with growth hormone deficiency (GHD). This twelve-month observational study was to assess adherence in r-hGH patients treated with the easypod™, an electronic, fully automated injection device designed to track the time, date and dose administered. METHODS: Ninety-seven prepubertal patients receiving r-hGH therapy were included in the study from ten Italian clinical sites and 88 completed the study. To avoid possible confounding effects, only GHD patients (79/88; 89.7 % of the overall study population) were considered in the final analysis. The primary endpoint-adherence to treatment-was calculated as the proportion of injections correctly administered during the observational period out of the expected total number of injections. The relevant information, tracked by the easypod™, was collected at months 6 (V1) and 12 (V2) after baseline (V0). At study termination, adherence data were partially available from 16 patients and fully available from 53 patients. As secondary endpoints, serum IGF-1 levels, fasting serum glucose and insulin levels and key anthropometric characteristics (height, waist circumference and BMI) were also determined. RESULTS: The easypod™ data showed that 56.7 % of the patients were considered to be fully (≥92 %) adherent to their treatment throughout the period V0-V2. Treatment improved stature, significantly increased IGF-1 and produced a non-significant increase in blood glucose and insulin levels. CONCLUSIONS: The injection-recording system and other characteristics of easypod™ could enhance the ability of physicians to monitor adherence to r-hGH treatment.

Growth hormone treatment of adolescents with growth hormone deficiency (GHD) during the transition period: results of a survey among adult and paediatric endocrinologists from Italy. Endorsed by SIEDP/ISPED, AME, SIE, SIMA.

Treatment of adolescents with growth hormone deficiency (GHD) during the transition period is a controversial issue. This paper is a contribution from the Italian community of paediatric and adult endocrinologists surveyed in a Delphi panel. The Delphi method is a structured communication technique, originally developed as a systematic, interactive forecasting method that relies on a panel of experts. The experts answer questionnaires in two or more rounds. There was substantial agreement on the definition of the problems associated with the diagnosis and treatment of adolescents with GHD in the transition period, as well as on the identification of the controversial issues which need further studies. There is general consensus on the need of re-testing all isolated idiopathic GHD after at least 30-day withdrawn from treatment, while in patients with multiple pituitary deficiency and low IGF-I levels there is generally no need to re-test. In patients with permanent or confirmed GHD, a starting low rhGH dose (0.01-0.03 mg per day) to be adjusted according to IGF-I concentrations is also widely accepted. For those continuing treatment, the optimal therapeutic schedule to obtain full somatic maturation, normalization of body composition and bone density, cardiovascular function and Quality of Life, need to be evaluated.

Correlation between cortisol and components of the metabolic syndrome in obese children and adolescents.

BACKGROUND: In obese subjects it has been shown that cortisol (F) contributes to the reduction in insulin sensitivity, suggesting a role in the development of the metabolic syndrome (MS). AIM: The aim of this retrospective study was to evaluate the relationship between F and components of MS in 1,027 obese children and adolescents. SUBJECTS AND METHODS: Waist circumference, systolic and diastolic blood pressure (SP, DP), F, serum glucose (Glyc), cholesterol HDL, triglycerides and homeostatic model assessment (HOMA index) were evaluated in all subjects. MS was defined according to the International Diabetes Federation criteria. Accordingly, patients were subdivided into three age groups: 6-10, 10-16 and >16 years. RESULTS: In univariate regression analysis, F was correlated with Glyc, SP and HOMA in groups 1 and 2, with DP in Group 2. In multivariate regression analysis including age, sex, puberty, BMI-SDS and F as independent variables and one of the component of the MS as the dependent variable, F was a weak predictor of the variability when DP and Glyc were introduced as dependent variables in Group 2 and when SP was introduced as dependent variable both in groups 1 and 2. When patients were subdivided into subgroups according to the IDF criteria, in Group 2 patients with one or more components of the MS had higher F concentrations. CONCLUSIONS: In this cohort of obese children and adolescents, F was weakly associated with components of the MS. These findings do not support a major role for F in the development of MS.

Prevalence of Type 1 diabetes autoantibodies (GAD and IA2) in Sardinian children and adolescents with autoimmune thyroiditis.

AIMS: Type 1 diabetes and autoimmune thyroiditis are common autoimmune diseases characterized by the presence of autoantibodies against tissue-specific components. Non-thyroid-specific autoantibodies are frequent in patients with autoimmune thyroiditis. The prevalence of Type 1 diabetes autoantibodies in patients with autoimmune thyroiditis is unknown. METHODS: The prevalence of Type 1 diabetes autoantibodies (GAD and IA2) was analysed in 236 Sardinian children and adolescents with autoimmune thyroiditis. GAD and IA2 antibodies were measured at the time of the diagnosis of autoimmune thyroiditis and re-evaluated after 1 year in the children who were shown to be positive. Autoantibody prevalence was evaluated in 949 healthy age-matched controls. RESULTS: The prevalence of GAD and/or IA2 antibodies was 8% in the children and adolescents with autoimmune thyroiditis and 4.1% in control subjects (P = 0.017). When Type 1 diabetes autoantibodies were separately analysed, the difference remained significant for IA2 (3.39% in autoimmune thyroiditis vs. 1.16% in control subjects, P = 0.012), but not for GAD (5.1% in autoimmune thyroiditis vs. 3.79% in control subjects, P = 0.367). Seven of 10 children with autoimmune thyroiditis and detectable Type 1 diabetes autoantibodies at the diagnosis remained positive after 1 year. In the course of 2 years of follow-up, two patients who were positive for Type 1 diabetes autoantibodies at the time of diagnosis of autoimmune thyroiditis developed diabetes. CONCLUSIONS: This is the first study reporting the prevalence of Type 1 diabetes autoantibodies in a selected cohort of genetically homogeneous children and adolescents with autoimmune thyroiditis. The main finding was that the prevalence of Type 1 diabetes autoantibodies and of newly diagnosed Type 1 diabetes in patients with autoimmune thyroiditis was significantly higher than that observed in the general paediatric population, suggesting that children with autoimmune thyroiditis are at increased risk of developing Type 1 diabetes.

Growth hormone response to physical exercise in growing patients with classic congenital adrenal hyperplasia.

Glucocorticoid over-treatment in children with congenital adrenal hyperplasia (CAH) may suppress GH secretion and growth. Aims of our study were: 1) to evaluate post-exercise GH response in patients affected by CAH due to 21-hydroxylase deficiency, in comparison with a group of healthy subjects; 2) to investigate the relationship between the hormonal markers of adequate steroid therapy and GH secretion. We evaluated GH secretion every 6 months in 20 young CAH patients (8 girls, 12 boys). Mean follow-up was 4.6+/-0.9 yr (107 tests performed, 5.35+/-2.05 repeated tests for each patient). Forty-four healthy subjects (25 boys, 19 girls) were selected as a control group. The range of post-exercise GH peak was very wide, but medians were not statistically different in cases and controls (p=0.570). Multivariate analysis showed that post-exercise GH peak was not related to age (p=0.743), gender (p=0.296) or pubertal status (p=0.440) in both groups. GH increase from baseline showed the same behavior (p=0.265, 0.639 and 0.105, respectively). In CAH patients, GH peak and GH increase were both directly related to 17-OH-progesterone levels [GH peak: p=0.032--95% confidence interval (CI): 0.01-0.34--beta=0.18; GH increase: p=0.008--95% CI: 0.06-0.35--beta=0.20]. The negative effect of glucocorticoid therapy on GH secretion seems to be dominant in CAH. The most effective approach to adjust treatment remains monitoring growth. Relying on hormonal markers to adequate steroid therapy may result in over-treatment, GH suppression, and finally poor linear growth.

The effect of puberty on insulin resistance in obese children.

OBJECTIVE: Insulin resistance (IR) increases during puberty in normal children. IR is the first adverse metabolic event of obesity, and the marker of the metabolic syndrome. We aimed to study the effect of puberty on IR in obese and normal-weight children. DESIGN: Cross-sectional evaluation of fasting glucose, insulin concentrations, and homeostasis model assessment of IR (HOMA-IR) in obese and control children throughout puberty. PATIENTS AND METHODS: We recruited 424 obese children (207 pre-pubertal and 217 pubertal divided in Tanner stages 2-3, 4, and 5) and estimated IR using the HOMA-IR index. Data were compared to those obtained in 123 healthy normal-weight children (40 pre-pubertal and 83 pubertal divided in Tanner stages 2-3, 4, and 5). RESULTS: In the obese children mean HOMA-IR increased progressively across Tanner stages, and was significantly higher in all groups (pre-pubertal and Tanner stages 2-3, 4, and 5) of obese than in control children. HOMA-IR was significantly correlated with BMI. CONCLUSIONS: HOMA-IR in obese children increases at puberty more than in normal-weight children and does not return to pre-pubertal values at the end of puberty.

Assessment of serum IGF-I concentrations in the diagnosis of isolated childhood-onset GH deficiency: a proposal of the Italian Society for Pediatric Endocrinology and Diabetes (SIEDP/ISPED).

The diagnosis of GH deficiency (GHD) is based on the measurement of peak GH responses to pharmacological stimuli. Pharmacological stimuli, however, lack precision, accuracy, are not reproducible, are invasive, non-physiological and some may even be hazardous. Furthermore, different GH commercial assays used to measure GH in serum yield results that may differ considerably. In contrast to GH, IGF-I can be measured on a single, randomly-obtained blood sample. A review of the available data indicates that IGF-I measurement in the diagnosis of childhood-onset isolated GHD has a specificity of up to 100%, with a sensitivity ranging from about 70 to 90%. We suggest an algorithm in which circulating levels of IGF-I together with the evaluation of auxological data, such as growth rate and growth, may be used to assess the likelihood of GHD in pre-pubertal children.

Evaluation of adrenal function in patients with growth hormone deficiency and hypothalamic-pituitary disorders: comparison between insulin-induced hypoglycemia, low-dose ACTH, standard ACTH and CRH stimulation tests.

OBJECTIVES: Patients with organic growth hormone deficiency (GHD) or with structural hypothalamic-pituitary abnormalities may have additional anterior pituitary hormone deficits, and are at risk of developing complete or partial corticotropin (ACTH) deficiency. Evaluation of the integrity of the hypothalamic-pituitary-adrenal axis (HPA) is essential in these patients because, although clinically asymptomatic, their HPA cannot appropriately react to stressful stimuli with potentially life-threatening consequences. DESIGN AND METHODS: In this study we evaluated the integrity of the HPA in 24 patients (age 4.2-31 years at the time of the study) with an established diagnosis of GHD and compared the reliability of the insulin tolerance test (ITT), short synacthen test (SST), low-dose SST (LDSST), and corticotropin releasing hormone (CRH) test in the diagnosis of adrenal insufficiency. RESULTS: At a cortisol cut-off for a normal response of 550 nmol/l (20 microg/dl), the response to ITT was subnormal in 11 subjects, 6 with congenital and 5 with acquired GHD. Four patients had overt adrenal insufficiency, with morning cortisol concentrations ranging between 66.2-135.2 nmol/l (2.4-4.9 microg/dl) and typical clinical symptoms and laboratory findings. In all these patients, a subnormal cortisol response to ITT was confirmed by LDSST and by CRH tests. SST failed to identify one of the patients as adrenal insufficient. In the seven asymptomatic patients with a subnormal cortisol response to ITT, the diagnosis of adrenal insufficiency was confirmed in one by LDSST, in none by SST, and in five by CRH tests. The five patients with a normal cortisol response to ITT exhibited a normal response also after LDSST and SST. Only two of them had a normal response after a CRH test. In the seven patients with asymptomatic adrenal insufficiency mean morning cortisol concentration was significantly higher than in the patients with overt adrenal insufficiency. ITT was contraindicated in eight patients, and none of them had clinical symptoms of overt adrenal insufficiency. One of these patients had a subnormal cortisol response to LDSST, SST, and CRH, and three exhibited a subnormal response to CRH but normal responses to LDSST and to SST. CONCLUSION: We conclude that none of these tests can be considered completely reliable for establishing or excluding the presence of secondary or tertiary adrenal insufficiency. Consequently, clinical judgment remains one of the most important issues for deciding which patients need assessment or re-assessment of adrenal function.

Epinephrine mediates the growth hormone-releasing effect of galanin in infant rats.

The mechanism underlying the GH-releasing effect of galanin (GAL), a novel 29-amino acid peptide, was investigated in the neonatal rat. The effect of galanin was compared to that of clonidine (CLO), a drug known to release GH via endogenous GHRF. GAL administration (5-25 micrograms/kg BW, sc) induced in 10-day-old pups a clear-cut and dose-related rise in plasma GH 15 min postinjection. CLO (50-450 micrograms/kg BW, sc) induced a marked rise in plasma GH, but no dose-related effect was evident. Inhibition of hypothalamic norepinephrine and epinephrine biosynthesis by DU-18288 (6 mg/kg BW, ip) or selective inhibition of epinephrine biosynthesis by SKF-64139 (50 mg/kg BW, ip) completely abolished the GH-releasing effect of GAL (25 micrograms/kg, sc), but left unaltered the GH rise induced by CLO (150 micrograms/kg, sc). Passive immunization with an anti-GHRF serum decreased basal GH levels and prevented the GH-releasing effect of either GAL or CLO, whereas in pups pretreated with an antisomatostatin serum, CLO, but not GAL, increased the already elevated plasma GH titers. In all these data indicate that in the infant rat 1) GAL is a potent GH secretagogue; 2) the action of GAL is not exerted directly on GHRF- or somatostatin-secreting structures, but requires the intervention of catecholaminergic neurons; 3) the GH-releasing effect of GAL is ultimately exerted via GHRF release, although a mechanism operating to inhibit hypothalamic somatostatin release cannot be ruled out; and 4) differently from GAL, CLO releases GH via postsynaptic stimulation of GHRF-secreting neurons.

Augmentation of growth hormone secretion in children with constitutional growth delay by short term clonidine administration: a pulse amplitude-modulated phenomenon.

We evaluated the effect of chronic clonidine administration on 24-h integrated GH secretion (IC-GH) in eight children (six boys and two girls; age, 6.0-13.0 yr) with constitutional growth delay (CGD). Clonidine was given orally in a daily dose of 0.1 mg/m2 at bedtime for 6 months; 24-h secretion studies were performed before and after 2 months of treatment. Clonidine caused a significant augmentation (P less than 0.02) of mean IC-GH from 2.6 +/- 0.4 (+/- SE) to 4.6 +/- 0.6 micrograms/L. The increase in IC-GH was mainly the result of increased GH pulse amplitude, which rose from 12.3 +/- 1.3 to 18.2 +/- 2.1 micrograms/L (P less than 0.01). The mean GH pulse amplitude was significantly higher (P less than 0.02) during sleep (15.9 +/- 2.4 micrograms/L) than during the awake hours (8.4 +/- 1.5 micrograms/L) before treatment. During clonidine treatment the mean GH pulse amplitude during the awake hours (15.0 +/- 3.8 micrograms/L) was similar to that during sleep (20.3 +/- 3.1 micrograms/L). GH pulse frequency was not altered by treatment during either the awake or sleep hours. The mean insulin-like growth factor I levels after 2 (1400 +/- 300 U/L) and 6 (1760 +/- 430 U/L) months of treatment were significantly higher (P less than 0.02 and P less than 0.05, respectively) than the pretreatment value (920 +/- 240 U/L). After 2 months of clonidine treatment, growth velocity increased from 3.1 +/- 0.5 to 10.2 +/- 1.0 cm/yr (P less than 0.001), and after 6 months of treatment is was still significantly higher (7.0 +/- 0.7 cm/yr; P less than 0.02) than that before treatment. These results confirm the ability of clonidine to accelerate growth in children with CGD and indicate that clonidine is capable of increasing IC-GH levels. They also reinforce the view that many children with CGD have decreased endogenous GH secretion.