RESUMO
BACKGROUND: Only one mathematical model to date describes human growth and its different phases from fetal life until adult height. AIM: To develop a model describing growth from fetal life to adult height taking maturation/biological tempo into consideration. SUBJECTS: The model was developed based on longitudinal mean height values obtained from published growth references for a cohort of 3650 healthy Swedish children followed from birth circa 1974 until adult height combined with birth-length for circa 400 000 healthy infants born 1990-1995. RESULTS: The QEPS-model for individual growth was constructed with a combination of four basic shape-invariant growth functions: a quadratic Q-function and a negative exponential E-function, both started during fetal life, 8 months before birth; the E-function levelled off after birth, whereas the Q-function continued until end of growth. A specific nonlinear pubertal P-function started at onset of puberty, and a stop S-function ended growth according to both the Q-function continuing during puberty and the specific P-function. For each function, an individual height-scale parameter was defined, and for the E- and P-functions, a time-scale parameter; giving six modifying parameters in total. In addition standardized proportional scores were used for biological interpretations. The QEPS-model was used to fit and generate mathematical functions suitable to describe the growth of the healthy population of Swedish children; thereafter, the model was modified using four height-scale parameters to model individual height in cm, and two time-scale parameters to adjust for the individual tempo of growth. Individual confidence intervals were calculated for all parameters. CONCLUSIONS: A new shape-invariant growth model, QEPS, was developed, that requires only four basic growth functions to describe the total pattern of growth in height from fetal life to adult height, with addition of height- and time-scale parameters describing individual growth. The model can describe a wide variety of growth curves. Moreover, it is the first model to provide confidence intervals which enable us to describe the precision/quality of individual parameters.
Assuntos
Desenvolvimento Fetal , Crescimento , Modelos Biológicos , Adulto , Estatura/fisiologia , Feminino , Humanos , Estudos Longitudinais , Masculino , Puberdade/fisiologiaRESUMO
OBJECTIVE: Daily subcutaneous self-injection of GH is used worldwide to treat short stature in childhood; longitudinal data on the impact of this regimen on GH-uptake are lacking. DESIGN: Children with/without GH-deficiency participating in clinical trials were followed prospectively (≤8 times). Blood was sampled pre-GH-injection (dose GH33/GH67⯵g/kg) and either every 30â¯min thereafter for 24â¯h (Experimental-setting; 59 GH-curves/15 children); or every 2â¯h thereafter for 16â¯h (Clinical-setting; 429 GH-curves/117 children). Pharmacokinetics were estimated by time Tmax (h) of maximal GH-concentration (Cmax, mU/L) and area under the curve for 16â¯h (AUC, mU/Lâ¯∗â¯h). RESULTS: In the Clinical-setting, median Cmax was 71â¯mU/L and AUC was 534â¯mU/Lâ¯∗â¯h, with coefficients of variation for intra-individual variation of 39% and 36%, respectively, and inter-individual variation of 44% and 42%, respectively. 43% of Cmax and AUC variability was explained by GH-dose and proxies for injection depth (baseline GH-level, GHpeakwidth, BMISDS). In the Experimental- versus Clinical-setting, 85% and 40% of GH-curves, respectively, reached zero-levels within 24â¯h. A longer duration was found following a more superficial GH-injection. Spontaneous GH-peaks were identified already 6â¯h after the GH-injection in about half of the curves of both GHD and non-GHD patients. CONCLUSION: Very broad intra-individual and inter-individual variability was found. A high GH-peak will optimize growth effects; the highest Cmax was found after a deep injection of GH at the higher dose and concentration. In as many as 60% of the children, GH remained detectable in serum after 24â¯h; a constant GH-level will promote IGF-I and metabolic effects.
Assuntos
Transtornos do Crescimento/sangue , Transtornos do Crescimento/patologia , Hormônio do Crescimento Humano/administração & dosagem , Hormônio do Crescimento Humano/sangue , Proteínas Recombinantes/administração & dosagem , Biomarcadores/sangue , Criança , Feminino , Seguimentos , Transtornos do Crescimento/tratamento farmacológico , Hormônio do Crescimento Humano/farmacocinética , Humanos , Injeções Subcutâneas , Masculino , Prognóstico , Estudos Prospectivos , Distribuição TecidualRESUMO
BACKGROUND: Mathematical models can be used to predict individual growth responses to growth hormone (GH) therapy. The aim of this study was to construct and validate high-precision models to predict the growth response to GH treatment of short children, independent of their GH status, birth size and gestational age. As the GH doses are included, these models can be used to individualize treatment. METHODS: Growth data from 415 short prepubertal children were used to construct models for predicting the growth response during the first years of GH therapy. The performance of the models was validated with data from a separate cohort of 112 children using the same inclusion criteria. RESULTS: Using only auxological data, the model had a standard error of the residuals (SDres), of 0.23 SDS. The model was improved when endocrine data (GHmax profile, IGF-I and leptin) collected before starting GH treatment were included. Inclusion of these data resulted in a decrease of the SDres to 0.15 SDS (corresponding to 1.1 cm in a 3-year-old child and 1.6 cm in a 7-year old). Validation of these models with a separate cohort, showed similar SDres for both types of models. Preterm children were not included in the Model group, but predictions for this group were within the expected range. CONCLUSION: These prediction models can with high accuracy be used to identify short children who will benefit from GH treatment. They are clinically useful as they are constructed using data from short children with a broad range of GH secretory status, birth size and gestational age.
Assuntos
Estatura/efeitos dos fármacos , Desenvolvimento Infantil/efeitos dos fármacos , Hormônio do Crescimento Humano/farmacologia , Hormônio do Crescimento Humano/uso terapêutico , Recém-Nascido Pequeno para a Idade Gestacional/crescimento & desenvolvimento , Modelos Estatísticos , Peso ao Nascer/fisiologia , Estatura/fisiologia , Peso Corporal/fisiologia , Criança , Estudos de Coortes , Tolerância a Medicamentos , Feminino , Hormônio do Crescimento Humano/administração & dosagem , Humanos , Lactente , Recém-Nascido , Insulina , Fator de Crescimento Insulin-Like I/metabolismo , Masculino , Valor Preditivo dos Testes , Resultado do TratamentoRESUMO
To facilitate the diagnosis of GH deficiency and monitor GH therapy, we constructed two reference models to allow comparison of serum IGF binding protein (IGFBP)-3 concentrations and IGF-I to IGFBP-3 ratios among children throughout childhood and adolescence. This report presents equations for determining the sd score of IGFBP-3 and IGF-I to IGFBP-3 measurements for individual patients. The data set contains serum values from 468 healthy children and adolescents (232 males, 236 females; ages 1.1-18.3 yr) whose height, weight, and body mass index were within +/- 3 sd of means. Puberty was classified according to breast development (B) and testicular volume into pre-, early, mid-, and late puberty. The values of IGFBP-3 and IGF-I to IGFBP-3 ratios were log transformed, and multiple linear regression analysis was used to identify models for converting serum concentrations into sd scores. The models include the variables of age, gender, and puberty and take into account the interactions among these variables. The best linear models explain 42% of the variation in serum IGFBP-3 concentrations and 50% of the variation in serum IGF-I to IGFBP-3 concentrations. The relationship between age and log(IGFBP-3) was positive for boys in pre-, early, and midpuberty. In late puberty, values were higher than earlier in puberty, and there was a negative relationship with age. For girls the relationship between age and log(IGFBP-3) also was positive in pre- and early puberty, with larger effect for girls older than 8 yr. Values for girls in midpuberty were relatively constant, and in late puberty values were higher than earlier in puberty, and there was a negative relationship with age. The relationship between age and log(IGF-I to IGFBP-3 ratio) was positive for boys in pre-, early, and early midpuberty (volume = 9-14 ml). In late midpuberty (volume = 15-19 ml), the relationship between age and IGF-I to IGFBP-3 ratio was negative. In late puberty, values were relatively constant and higher than earlier in puberty. For girls in prepuberty, the relationship with age was positive, with a larger effect in girls older than 8 yr. In early puberty, the girls' values were relatively constant. In early midpuberty (B = 3), log(IGF-I to IGFBP-3 ratio) values were higher for girls than boys of the same age. In late midpuberty (B = 4), the relationship with age was negative, and in late puberty values were relatively constant and higher than earlier in puberty.
Assuntos
Química Clínica/normas , Proteína 3 de Ligação a Fator de Crescimento Semelhante à Insulina/sangue , Fator de Crescimento Insulin-Like I/metabolismo , Adolescente , Composição Corporal , Criança , Estudos Transversais , Feminino , Humanos , Modelos Logísticos , Masculino , Puberdade/sangue , Valores de ReferênciaRESUMO
BACKGROUND/AIMS: Children with cystic fibrosis (CF) are of increased risk of reduced fat body mass (FBM) and lean body mass (LBM). Serum concentrations of insulin-like growth factor-1 (IGF-1)and leptin could be markers of LBM and/or FBM depletion. To evaluate the relationships between disease activity, body composition, IGF-1 and leptin concentrations in CF children. METHODS: A cross-sectional study with 26 CF children aged 5.0-15.5 years and 33 healthy controls, mean age 9.4 years. Body composition was evaluated by dual-energy X-ray absorptiometry. Fasting blood samples were analyzed for leptin, IGF-1 and IGFBP-3. RESULTS: FBM standard deviation score (SDS; CF boys -0.02 +/- 0.88 vs. 0.78 +/- 0.65, p < 0.01; CF girls -0.37 +/- 1.15 vs. 0.70 +/- 0.97, p < 0.05), leptin concentration (CF boys 2.07 +/- 0.79 vs. 3.07 +/- 1.28 ng/ml, p < 0.05; CF girls 2.71 +/- 0.86 vs. 5.00 +/- 2.95 ng/ml, p < 0.05) and IGF-1SDS (CF boys -1.43 +/- 1.50 vs. -0.32 +/- 0.88, p < 0.05; CF girls -0.66 +/- 1.66 vs. 0.64 +/- 0.57, p < 0.01) were lower in CF children compared to controls. Shwachman score was the strongest predictor of lean body mass (R = 0.63). Leptin levels explain 60% of the variability in FBM. CONCLUSION: Serum concentrations of IGF-1 and leptin are decreased in children with CF and are associated with clinical conditions and body composition.
Assuntos
Composição Corporal , Fibrose Cística/sangue , Fator de Crescimento Insulin-Like I/análise , Leptina/sangue , Tecido Adiposo/anatomia & histologia , Adolescente , Biomarcadores/sangue , Criança , Desenvolvimento Infantil , Pré-Escolar , Estudos Transversais , Feminino , Humanos , Inflamação/sangue , MasculinoRESUMO
OBJECTIVE: The purpose of this study was to analyze growth hormone (GH) concentrations in obese women before and after Roux-en-Y gastric bypass (RYGBP) and how resulting changes in weight, fat mass, ghrelin levels, and insulin sensitivity affect GH secretion. RESEARCH METHODS AND PROCEDURES: Blood was sampled at 20-minute intervals for 24 hours in 10 non-diabetic premenopausal severely obese women before and 6 months after RYGBP. GH concentrations were measured in all samples, and serum ghrelin was collected at five time-points. RESULTS: After a 27% BMI drop (55.9 +/- 6.2 to 40.7 +/- 5.8 kg/m2), blunted GH profiles underwent partial recovery. Basal, postprandial, and mean ghrelin concentrations were not changed. A negative correlation was found between mean GH levels and insulin and homeostasis model assessment (p < 0.01). BMI accounted for 54% of GH variation. DISCUSSION: Partial recovery of GH secretion after RYGBP-induced weight loss suggests that a blunted secretion is not a causal factor of obesity but a consequence of the obese state and does not seem to be ghrelin-level dependent.
Assuntos
Derivação Gástrica , Hormônio do Crescimento/metabolismo , Obesidade/sangue , Obesidade/cirurgia , Hormônios Peptídicos/metabolismo , Adulto , Composição Corporal , Peso Corporal/fisiologia , Feminino , Grelina , Hormônio do Crescimento/sangue , Humanos , Resistência à Insulina/fisiologia , Estudos Longitudinais , Pessoa de Meia-Idade , Obesidade/fisiopatologia , Hormônios Peptídicos/sangue , Período Pós-Prandial/fisiologia , Estudos ProspectivosRESUMO
OBJECTIVE: To investigate the characteristics of spontaneous GH secretion in four male children with short stature due to partial GH insensitivity. Their molecular defect consists of inclusion of a mutant intronic pseudoexon in the region of the GH receptor involved in homodimerization. SUBJECTS: The subjects were two pairs of brothers who were first cousins, aged 10.4-14.2 years, heights -3.3 to -5.6 SDS, from a consanguineous Pakistani family. Basal serum IGF-I levels were extremely low (20-29 mg/l; NR > 50), with absent or minimal response to human recombinant GH (hGH) stimulation. Serum IGFBP-3 SDS levels were also low (-2.9 to -8.9). GH binding protein (GHBP) levels were normal (28.1-51.7%). METHODS: Spontaneous GH secretion was studied by intermittent (20 min) venous sampling from 2000 to 0800 h. The secretion profiles were analysed using the Pulsar programme and compared to data from a reference population of 76 prepubertal Swedish children [median age 10.7 years, median height -1.1 SDS (-2.0 to 1.4)] according to Swedish growth standards. RESULTS: Median (range) Pulsar-derived values in the four patients and controls were, respectively: GHmax (mU/l) 276.6 (178.7-325.8) and 27.2 (13.1-94.9), mean GH (mU/l) 64.5 (41.9-77.8) and 5.8 (3.2-20.6), baseline (mU/l) 12.3 (11.7-20.1) and 1.1 (0.2-6.1), AUCb (mU/l x 24 h) 1210 (684-1555) and 112.5 (60.6-316.4), i.e. all parameters of GH secretion in the four patients were markedly elevated compared with the control population. CONCLUSIONS: Spontaneous GH secretion is elevated in partial GH insensitivity. This investigation could be of diagnostic value in children with short stature.