The impact of gender, puberty and body mass on reference values for urinary growth hormone (GH) excretion in normally growing non-obese and obese children

Female Adolescents with Chronic or End-Stage Kidney Disease and Strategies for their Care

The prevalence of chronic or end-stage kidney disease in pediatric girls is lower than in boys, however, girls have unique morbidities that can have great effect on their quality of life. For female adolescents, creatinine excretion peaks at approximately 14 years of age and is significantly less than males, owing to lower muscle mass. Females have higher nitric oxide activity, and estrogens may contribute to lower blood pressure. Females excrete less growth hormone during the prepubertal and pubertal years. Females between the ages of 8 and 10 years show increased levels of parathyroid hormone and vitamin D, however, female adolescents with chronic kidney disease have less estrogen and loss of the luteinizing hormone pulsatile pattern. These biological, hormonal, and physical changes affect the psychosocial aspects of female adolescents with chronic kidney disease/end-stage kidney disease, and they must learn to manage their health to achieve good outcomes. Patients and their parents must learn disease management through a customized health care transition preparation in both the pediatric- and adult-focused settings. Clinical strategies are suggested for the care of these special patients.

Endocrinology, energetics, and human life history: A synthetic model

Human life histories are shaped by the allocation of metabolic energy to competing physiological domains. A model framework of the pathways of energy allocation is described and hormonal regulators of allocation along the pathways of the framework are discussed in the light of evidence from field studies of the endocrinology of human energetics. The framework is then used to generate simple models of two important life history transitions in humans, puberty and the postpartum return to full fecundity in females. The results of the models correspond very closely to observations made in the field.

Growth hormone doping in sports: a critical review of use and detection strategies

GH is believed to be widely employed in sports as a performance-enhancing substance. Its use in athletic competition is banned by the World Anti-Doping Agency, and athletes are required to submit to testing for GH exposure. Detection of GH doping is challenging for several reasons including identity/similarity of exogenous to endogenous GH, short half-life, complex and fluctuating secretory dynamics of GH, and a very low urinary excretion rate. The detection test currently in use (GH isoform test) exploits the difference between recombinant GH (pure 22K-GH) and the heterogeneous nature of endogenous GH (several isoforms). Its main limitation is the short window of opportunity for detection (~12-24 h after the last GH dose). A second test to be implemented soon (the biomarker test) is based on stimulation of IGF-I and collagen III synthesis by GH. It has a longer window of opportunity (1-2 wk) but is less specific and presents a variety of technical challenges. GH doping in a larger sense also includes doping with GH secretagogues and IGF-I and its analogs. The scientific evidence for the ergogenicity of GH is weak, a fact that is not widely appreciated in athletic circles or by the general public. Also insufficiently appreciated is the risk of serious health consequences associated with high-dose, prolonged GH use. This review discusses the GH biology relevant to GH doping; the virtues and limitations of detection tests in blood, urine, and saliva; secretagogue efficacy; IGF-I doping; and information about the effectiveness of GH as a performance-enhancing agent.

Glucose tolerance status in 510 children and adolescents attending an obesity clinic in Central Italy

Childhood obesity is epidemic in developed countries and is accompanied by an increase in the prevalence of type 2 diabetes (T2DM).

AIMS

Establish prevalence of glucose metabolism alterations in a large sample of overweight/obese children and adolescents from Central Italy.

METHODS

The study group included 510 overweight/obese subjects (3-18 yr). Oral glucose tolerance test (OGTT) was performed with glucose and insulin determination. Homeostatic model assessment of insulin resistance (HOMA-IR) and insulin sensitivity index (ISI) were derived from fasting and OGTT measurements. Beta-cell function was estimated by insulinogenic index. Fat mass was measured by dual-energy x-ray absorptiometry.

RESULTS

Glucose metabolism alterations were detected in 12.4% of patients. Impaired glucose tolerance (IGT) was the most frequent alteration (11.2%), with a higher prevalence in adolescents than in children (14.8 vs. 4.1%, p < 0.001); silent T2DM was identified in two adolescents (0.4%). HOMA-IR and glucose-stimulated insulin levels were higher in patients with IGT than individuals with normal glucose tolerance (HOMA-IR = 4.4 +/- 2.5 vs. 3.4 +/- 2.3, p = 0.001). Fat mass percentage and insulinogenic index were not different between the two groups. In multivariate analysis, age, fasting glucose, and insulin resistance influenced independently plasma glucose at 120 min of OGTT. Individuals with combined impaired fasting glucose/IGT (IFG/IGT) and T2DM were older and had reduced plasma insulin values at OGTT when compared to patients with simple IGT.

CONCLUSIONS

Glucose metabolism alterations are frequently found among children and adolescents with overweight/obesity from Central Italy. Age, fasting glucose, and insulin resistance are main predictors of IGT. We suggest the use of OGTT as a screening tool in obese European adolescents.

Association between white blood cell count and components of metabolic syndrome

BACKGROUND

Components of metabolic syndrome (MetS) were found to be associated with several inflammatory factors including white blood cell count (WBCC), which is an easily available test in clinical practice. In the present study, the relationships between WBCC and MetS components were investigated in children.

METHODS

A total of 288 Taiwanese children, under 10 years old, with normal WBCC, were enrolled in the study. They were divided into quartiles according to WBCC (lowest, WBCC1; highest, WBCC4). The mean values of each MetS component for every group were compared in boys and girls separately. Multivariate linear regression between the WBCC and the MetS components after adjusting for age and body mass index (BMI) were also evaluated.

RESULTS

In group comparison, only the high-density lipoprotein-cholesterol (HDL-C) was found to be significantly lower in WBCC4 in boys. Other components were not different. After multivariate linear regression, WBCC was negatively correlated to HDL-C and positively to BMI in boys. Although not significant, similar relationships were also observed in girls. Interestingly, borderline positive correlation was noted between triglyceride (TG) and WBCC in girls.

CONCLUSION

BMI was positively and HDL-C was negatively related to WBCC in boys. A similar trend could also be observed in girls but without significance. Borderline significant correlation between TG and WBCC was noted in girls. These findings suggest that cardiovascular risks might commence even in childhood. Early detection of children with these abnormalities may help to prevent cardiovascular disease and diabetes in adolescence or even adulthood.

Growth hormone, IGF-1, insulin, SHBG, and estradiol levels in girls before menarche

The timing of pubertal changes depends on the concerted function of the hypothalamic - pituitary - ovarian and other endocrine systems. The somatotropin system and insulin play important roles during the growth and maturation of girls. Our clinical observations have enabled us to determine and implement criteria that split the pre-menarcheal period into three phases with distinct features associated with rising levels of estrogens (pre-estrogenization, onset of estrogenization and full estrogenization). The aim of this work was to determine levels of growth hormone, insulin - like growth factor 1 (IGF-1), sex hormone binding globulins (SHBG), insulin, and estradiol in relation to somatic features in girls during subsequent phases of estrogenization. This prospective study was done in 45 healthy girls. Every three months, we recorded weight, height, BMI, maturation of tertiary sex features, estrogen-related changes in hymen, sonographic dimensions of ovaries and uterus and serum levels of growth hormone, IGF-1, SHBG, insulin, and estradiol. Onset of estrogenization was accompanied by reduction of body mass and slowing down of growth associated with declining levels of growth hormone. These changes were followed by weight gain, pubertal acceleration of growth, rising levels of growth hormone, IGF-1, insulin, and estradiol, and falling levels of SHBG.

The impact of gender, body dimension and body composition on hand-grip strength in healthy children

Maximum hand-grip (HG) strength, body composition and main anthropometric variables were evaluated in 278 children with normal weight and growth, aged 5-15 yr divided into 3 age groups: group 1, age+/-SD: 7.6+/-0.9 yr 7.6+/-0.9 SD (Tanner stage 1); group 2, age: 10.8+/-0.7 yr (Tanner stage: 2-3); group 3, age: 13.2+/-0.9 yr (Tanner stage: 4-5). Weight, height, body surface area (BSA), BMI, percent body fat (BF) and fat free mass (FFM) increased progressively and significantly from the younger to the older age group. A significant difference between genders was detected only for BF and FFM, females having a higher fat mass and a lower FFM compared to males. Most children were right-handed (91%). In either genders, a curvilinear relation was detected between HG strength and age, with best fit for the dominant (d) hand given by the equations: dHG=5.891 *10(0.051) age, r2=0.986, p<0.001 in males and dHG=6.163 *10(0.045) age r2=0.973, p<0.001 in females. The increase in HG strength after 11 yr appears to be steeper in males as compared with that found in females. In both d and non-dominant (nd) hand, a significant difference in HG strength was detected between males and females, the average difference being about 10% at all ages. For both genders, nd hand was significantly weaker than d hand in the older age groups (2 and 3), but not in the younger group 1. Age and gender-dependent differences in HG strength (but not differences between d and nd hand) disappear if HG strength is normalized for FFM. Thus, in general, dHG strength normalized for FFM resulted on average to be 0.67+/-0.11 kg/kg. A multiple linear regression analysis indicated that HG was positively correlated with BMI, BSA, stature, stature2 and FFM (p<0.001 for all correlations) without differences between genders, while a negative correlation was found between HG strength and %BF. The most significant correlation was found between HG strength and FFM, without any significant difference between genders, so that the overall equation describing the line for the d hand was: dHG strength= 2.32+0.63 FFM, r2=0.72, p<0.001. In conclusion, the present study indicates that the age-dependent increase of HG strength as well as the between-gender differences are strongly related to changes of FFM values occurring during childhood. Moreover, the study provides a standard normative value of maximal HG strength for the healthy children population in Northern Italy.

Plasma and urinary GH following a standardized exercise protocol to assess GH production in short children

Plasma and urinary GH responses following acute physical exercise were evaluated in 19 short-statured children (12 males, 7 females, median age: 11.4 yr, age range: 6.1-14.5 yr, Tanner stage I-III, height < or = 3rd centile for age; 7 with familial short stature, FSS; 8 with constitutional growth delay, CGD; 4 with GH deficiency, GHD) and 7 normally growing, age- and sex-matched control children (4 males, 3 females, median age 11.0 yr, range: 7.2-13.1 yr, Tanner stage I-III). All patients and controls underwent a standardized exercise protocol (consisting of jogging up and down a corridor for 15 min, strongly encouraged to produce the maximum possible effort, corresponding to 70-80% of the maximal heart rate) after an overnight fasting. Samples for plasma GH determinations were drawn at 0 time (baseline), at 20 min (5 min after the end of exercise) and at 35 min (after 20 min of rest); urine samples were collected before (0 time) and at 40, 80 and 120 min after exercise. The distance covered by children with GHD during the test was significantly lower (p<0.05) than in the other groups of patients and controls. No differences in the pattern of plasma GH responses after physical exercise were found between children with FSS, CGD and healthy controls, the maximum percent increase (vs baseline) being evident at 20 min (median, FSS: +1125%; CGD: +1271%; controls: +571%). Children with GHD showed a smaller percent increase (+94%) of plasma GH, significantly lower (p<0.01) than those recorded in the other groups. A significant percent increase (p<0.01) of baseline urinary GH following exercise was found in children with FSS (median: +34%), CGD (+18%) and controls (+44%). Children with FSS and CGD showed a gradual increase of urinary GH, reaching the maximum at 80 min, while healthy controls had a more evident and precocious increase (maximum at 40 min). Urinary median GH levels did not change following physical exercise in children with GHD (-5%, not significant). A significant correlation was found between the maximal percent increase (vs baseline) of plasma and urinary GH following physical exercise (r=0.7, p<0.001). In conclusion, our results show that: 1) plasma and urinary GH responses (as well as the distance covered and the number of steps, i.e. the physical performance) to a standardized exercise protocol are similar in children with FSS, CGD and in normal-statured controls, being unable to differentiate among the "normal variants" of growth; 2) children with GHD, unable to accomplish the same performance of the other three groups, show significantly reduced plasma and urinary GH responses following physical exercise. Although the determination of GH responses to pharmacological stimuli remains the definitive tool for the diagnosis of GHD, these preliminary results seem to suggest a potential role of urinary (and plasma) GH response to a standardized exercise protocol as a safe, acceptable first screening test for GH sufficiency also in children, as previously reported in adults.