Home Use of an Artificial Beta Cell in Type 1 Diabetes.

BACKGROUND: The feasibility, safety, and efficacy of prolonged use of an artificial beta cell (closed-loop insulin-delivery system) in the home setting have not been established. METHODS: In two multicenter, crossover, randomized, controlled studies conducted under free-living home conditions, we compared closed-loop insulin delivery with sensor-augmented pump therapy in 58 patients with type 1 diabetes. The closed-loop system was used day and night by 33 adults and overnight by 25 children and adolescents. Participants used the closed-loop system for a 12-week period and sensor-augmented pump therapy (control) for a similar period. The primary end point was the proportion of time that the glucose level was between 70 mg and 180 mg per deciliter for adults and between 70 mg and 145 mg per deciliter for children and adolescents. RESULTS: Among adults, the proportion of time that the glucose level was in the target range was 11.0 percentage points (95% confidence interval [CI], 8.1 to 13.8) greater with the use of the closed-loop system day and night than with control therapy (P<0.001). The mean glucose level was lower during the closed-loop phase than during the control phase (difference, -11 mg per deciliter; 95% CI, -17 to -6; P<0.001), as were the area under the curve for the period when the glucose level was less than 63 mg per deciliter (39% lower; 95% CI, 24 to 51; P<0.001) and the mean glycated hemoglobin level (difference, -0.3%; 95% CI, -0.5 to -0.1; P=0.002). Among children and adolescents, the proportion of time with the nighttime glucose level in the target range was higher during the closed-loop phase than during the control phase (by 24.7 percentage points; 95% CI, 20.6 to 28.7; P<0.001), and the mean nighttime glucose level was lower (difference, -29 mg per deciliter; 95% CI, -39 to -20; P<0.001). The area under the curve for the period in which the day-and-night glucose levels were less than 63 mg per deciliter was lower by 42% (95% CI, 4 to 65; P=0.03). Three severe hypoglycemic episodes occurred during the closed-loop phase when the closed-loop system was not in use. CONCLUSIONS: Among patients with type 1 diabetes, 12-week use of a closed-loop system, as compared with sensor-augmented pump therapy, improved glucose control, reduced hypoglycemia, and, in adults, resulted in a lower glycated hemoglobin level. (Funded by the JDRF and others; AP@home04 and APCam08 ClinicalTrials.gov numbers, NCT01961622 and NCT01778348.).

Obesity in children with congenital adrenal hyperplasia in the Minnesota cohort: importance of adjusting body mass index for height-age.

OBJECTIVES: To evaluate obesity and overweight in children with congenital adrenal hyperplasia (CAH) and associations with glucocorticoids, fludrocortisone and disease control. Adjusting body mass index-for-height-age (BMIHA ) percentile is proposed to correct misclassification of obese/overweight status in CAH children with advanced bone age and tall-for-age stature. DESIGN: Longitudinal. PATIENTS: One hundred and ninety-four children with CAH seen from 1970 to 2013: 124 salt wasting (SW); 70 simple virilizing (SV); 102 females. MEASUREMENTS: Body mass index (BMI) end-points were overweight (85-94 percentile) and obese (≥95 percentile). RESULTS: Approximately 50% of the children had at least one BMI measurement ≥95 percentile and about 70% had at least one ≥85 percentile. Using BMIHA percentiles, obesity incidence decreased slightly in SW children (47-43%) and markedly in SV children (50-33%); however, overweight status was not reduced. Only 6% of SW and 1% of SV children were persistently obese (≥3 clinic visits) when BMIHA was applied, whereas overweight status persisted in 35% of SW and 33% of SV children. Most obesity or overweight when using BMIHA occurred before age 10 and there was no association with hydrocortisone (HC) or fludrocortisone dosing. Adiposity rebound for SW children occurred by 3·3 years and in SV females by age 3·8 years, over a year earlier than the adiposity rebound for healthy children. CONCLUSION: Children with CAH are at higher risk for early onset obesity and overweight with or without using BMIHA but rates of persistent obesity were lower than previously reported. Careful HC dosing during early childhood is needed to prevent increased weight gain and an early adiposity rebound.

Deprivation and ethnicity impact on diabetes control and use of treatment regimen.

AIMS: Deprivation and/or ethnicity impact on care delivery. We have assessed how these factors influence diabetes care in a paediatric clinic. METHODS: We related access to care [type of insulin treatment regimen-twice daily, multiple daily injections and insulin pump therapy (continuous subcutaneous insulin infusion)], measures of care process (HbA(1c)) and an approximate measure of satisfaction with the service (clinic attendance rate) in 325 (170 male) children and young people with Type 1 diabetes (mean age 10.6 years, mean duration of diabetes of 4.5 years), with indices of deprivation and ethnicity. RESULTS: Of the 325 children and young people, 2.7% received twice-daily insulin, 48.4% multiple daily injections and 48.9% continuous subcutaneous insulin infusion. Median clinic HbA(1c) was 62 mmol/mol (7.8%) and those receiving the insulin pump therapy had the lowest HbA(1c). Four ethnic groups were represented; White British 81.6%, Asian non-Indian 6.5%, African 8.1% and Asian Indian 3.8%. Mean deprivation score was 21.06. White British and Asian Indian groups were more likely to receive insulin pump therapy (χ(2) = 50.3; P < 0.001). Attendance rates were 94.1% and did not differ across ethnic groups. Deprivation was related to ethnicity and HbA(1c) (R(2) = 0.02; P = 0.02). There was no relationship between clinic attendance and deprivation. Insulin regimen and ethnicity were associated with HbA(1c) (R(2) = 0.096; P < 0.001). Similar findings were obtained when analysis was confined to the White British population. CONCLUSIONS: These data suggest that deprivation and ethnicity influence diabetes control and how intensive insulin therapy is utilized. A better consideration of the needs of different ethnic groups is required to ensure equitable care delivery in paediatric diabetes.

Mutations in the homeobox gene HESX1/Hesx1 associated with septo-optic dysplasia in human and mouse.

During early mouse development the homeobox gene Hesx1 is expressed in prospective forebrain tissue, but later becomes restricted to Rathke's pouch, the primordium of the anterior pituitary gland. Mice lacking Hesx1 exhibit variable anterior CNS defects and pituitary dysplasia. Mutants have a reduced prosencephalon, anopthalmia or micropthalmia, defective olfactory development and bifurcations in Rathke's pouch. Neonates exhibit abnormalities in the corpus callosum, the anterior and hippocampal commissures, and the septum pellucidum. A comparable and equally variable phenotype in humans is septo-optic dysplasia (SOD). We have cloned human HESX1 and screened for mutations in affected individuals. Two siblings with SOD were homozygous for an Arg53Cys missense mutation within the HESX1 homeodomain which destroyed its ability to bind target DNA. These data suggest an important role for Hesx1/HESX1 in forebrain, midline and pituitary development in mouse and human.

The relationship between body mass index and mid-arm circumference in a pregnant population.

Our objective was to correlate body mass index (BMI) with mid-arm circumference (MAC) and also to ascertain whether maternal BMI could be calculated from MAC at booking. We approached all Caucasian women who met the inclusion criteria attending the University College Hospital, London between 1 April 1996 and 30 June 1997 and the Rotunda Hospital, Dublin, Ireland between 15 April 2003 and 19 May 2004. A total of 2,912 women agreed to participate in the research. The participants' maternal height and weight were measured. Their BMI was calculated using the formula: BMI = weight (kg) ÷ height (m(2)). The MAC was measured in cm. Statistical analysis was performed using SPSS for Windows version 11 with p < 0.05 as significant. We found that BMI is directly correlated with MAC (r = 0.836) and estimates of BMI may be calculated from the simple equation BMI = MAC ± 2. Alternatively, a MAC of ≥ 27 cm allowed for a detection rate for overweight patients of 75%, with a false positive rate of 15%.

Do centimetres matter? Self-reported versus estimated height measurements in parents.

AIM: An impressive discrepancy between reported and measured parental height is often observed. The aims of this study were: (a) to assess whether there is a significant difference between the reported and measured parental height; (b) to focus on the reported and, thereafter, measured height of the partner; (c) to analyse its impact on the calculated target height range. METHODS/RESULTS: A total of 1542 individual parents were enrolled. The parents were subdivided into three groups: normal height (3-97th Centile), short (<3%) and tall (>97%) stature. Overall, compared with men, women were far better in estimating their own height (p < 0.001). Where both partners were of normal, short or tall stature, the estimated heights of their partner were quite accurate. Women of normal stature underestimated the short partner and overestimated the tall partner, whereas male partners of normal stature overestimated both their short as well as tall partners. Women of tall stature estimated the heights of their short partners correctly, whereas heights of normal statured men were underestimated. On the other hand, tall men overestimated the heights of their female partners who are of normal and short stature. Furthermore, women of short stature estimated the partners of normal stature adequately, and the heights of their tall partners were overestimated. Interestingly, the short men significantly underestimated the normal, but overestimated tall female partners. CONCLUSION: Only measured heights should be used to perform accurate evaluations of height, particularly when diagnostic tests or treatment interventions are contemplated. For clinical trails, we suggest that only quality measured parental heights are acceptable, as the errors incurred in estimates may enhance/conceal true treatment effects.

Plasma aldosterone response to the low-dose adrenocorticotrophin (ACTH 1-24) stimulation test.

BACKGROUND: Endocrine tests for adrenal insufficiency use pharmacological doses of stimulant such as ACTH. More physiological tests have often used high-dose protocols for sampling frequency. AIMS: To evaluate the response of plasma aldosterone concentration to low doses (125, 250 and 500 ng/m(2) body surface area) of synthetic ACTH. DESIGN: A randomised trial in six normal adult males aged 18-27 years. MATERIALS AND METHODS: Aldosterone concentration was measured by radioimmunoassay in serum from blood samples taken at 10 min intervals for 90 min. RESULTS: All three doses produced a significant rise in plasma aldosterone concentration (125 ng/m(2), P = 0.003; 250 ng/m(2), P < 0.001; 500 ng/m(2), P < 0.001) but there was no effect of dose on either the peak or incremental plasma aldosterone concentration. Mean time to peak was similar between the doses and the two higher doses were associated with a longer secretory profile (125 ng/m(2) 56 (26 SD) mins, 250 ng/m(2) 74 (19) mins, 500 ng/m(2) 77 (21) mins; F = 3.39; P = 0.04). Peaks of 100% were detected within 30 min of drug administration and peak response was associated with the prestimulation plasma aldosterone concentration (r = 0.45; P = 0.003). The between- and within-individual coefficients of variation for prestimulation concentrations were 37.0% and 32.8%, and for the peak response were 27.2% and 27.2%, respectively. CONCLUSIONS: The response of plasma aldosterone concentrations to low-dose ACTH administration requires a blood sampling protocol of 0, 10, 20 and 30 min to capture concentrations near the peak response. The high-dose protocol would have missed the response. Over the dose range studied no dose-response was observed so the selection of dose should be based on the dose effective to release steroids in the glucocorticoid pathway if this study is to be used in conjunction with such evaluation.

Childhood body mass index (BMI), breastfeeding and risk of Type 1 diabetes: findings from a longitudinal national birth cohort.

AIMS: To perform a longitudinal analysis of the association between childhood body mass index (BMI) and later risk of Type 1 diabetes, controlling for socio-economic status, birthweight, height in early and late childhood, breastfeeding history and pubertal status. METHODS: Analysis of the 1970 British Birth Cohort, followed up at age 5, 10 and 30 years (n = 11,261). Data were available on birthweight, breastfeeding; height, weight, pubertal status, socio-economic status at age 10 years; self-report data on history of diabetes (type, age at onset) at age 30 years. Cox proportional hazards models were used to examine relations of childhood growth, socio-economic status and breastfeeding history to the incidence of Type 1 diabetes between 10 and 30 years of age. RESULTS: Sixty-one subjects (0.5%) reported Type 1 diabetes at 30 years of age; 47 (77%) reported onset >or= age 10 years. Higher BMI z-score at 10 years predicted higher risk of subsequent Type 1 diabetes (hazard ratio 1.8, 95% confidence interval 1.2 to 2.8, P = 0.01) when adjusted for birthweight, pubertal status, breastfeeding history and socio-economic status. Repeating the model for childhood obesity, the hazard ratio was 3.1 (1.0, 9.3; P = 0.05). Birthweight, breastfeeding, height growth and pubertal timing were not associated with incidence of Type 1 diabetes. CONCLUSIONS: Higher BMI in childhood independently increased the risk of later Type 1 diabetes, supporting suggestions that obesity may provide a link between Type 1 and Type 2 diabetes. This supports observations of a rise in Type 1 diabetes prevalence. Reduction in childhood obesity may reduce the incidence of Type 1 as well as Type 2 diabetes.

A randomised study of two doses of biosynthetic human growth hormone on final height of pubertal children with growth hormone deficiency.

AIMS: To determine the effectiveness of different doses of r-hGH therapy during puberty in children with growth hormone deficiency (GHD). METHODS: Randomized controlled trial of different doses of r-hGH therapy administered during puberty in 49 children with GHD. The patients were allocated randomly using a random number table to one of two groups: group 1 (15 IU/m(2)/week) or group 2 (30 IU/m(2)/week). Patients were included if they had received r-hGH daily at a dose of 15 IU/m(2)/week (0.7 mg/m(2)/day) for at least 1 year before randomization. RESULTS: Height increase standard deviation scores (SDS) were similar between the two groups (group 1: 1.1; group 2: 1.2; p = 0.81). CONCLUSION: A higher dose of r-hGH administered during puberty does not appear to have a significant effect on final height of children with GH deficiency. Altering pubertal tempo or intensifying prepubertal r-hGH therapy may be a more promising approach to improving final height in children with GH deficiency.

A randomised study of the effect of two doses of biosynthetic human growth hormone on final height of children with familial short stature.

BACKGROUND/AIMS: The effects of biosynthetic human growth hormone (r-hGH) in children with familial short stature (FSS) are varied. We determined whether responsivity to r-hGH in FSS is dose-dependent. METHOD: Randomised trial of two doses (20 or 40 IU/m(2) body surface area/week by daily subcutaneous injection) of r-hGH in 29 (24 male, 5 female) FSS children with assessment at adult height. RESULTS: Age range at presentation was 5.1-10.5 years, height less than 1.5 standard deviation scores (SDS) below the mean, height velocity SDS greater than -1.5 and peak growth hormone response to provocative testing over 13.5 mU/l. Adult height data (SDS) at 16.5 +/- 2.1 years for the low-dose group and 16.1 +/- 1.1 years for the high-dose group (p = 0.62) were similar [low dose -1.06 (SD 0.75), high dose -1.02 (SD 0.83); p = 0.88]. The incremental effect of both doses on stature was minimal [low-dose difference in height actual-predicted 0.79 (SD 0.94), high dose 1.27 (SD 0.88); p = 0.12]. CONCLUSION: Using this r-hGH dosing schedule there were little short- or long-term effects on height in children with FSS.

Management of neonatal endocrinopathies--best practice guidelines.

Neonatal emergencies are uncommon, but may lead to significant morbidity and mortality if not recognised and managed promptly. Disorders of sex development, hypoglycaemia, thyrotoxicosis and calcium balance are discussed, with emphasis on the clinical assessment, investigations and management of these disorders in the acute setting.

Disturbed adrenal function in adolescents with chronic fatigue syndrome.

OBJECTIVE: To investigate adrenal function in children and adolescents with chronic fatigue syndrome (CFS) compared with age-matched controls. METHODS: Case-control study of low dose (500 ng/m2) synacthen tests (LDST) in 23 adolescents with CFS and 17 age-matched controls. Serum cortisol concentrations were measured at 5-min intervals from 10 to 45 minutes. Peak serum cortisol concentration, time to peak, rise in cortisol and area under the curve (AUC) were derived. RESULTS: Patients with CFS had significantly lower mean cortisol levels during the LDST (p <0.001), lower peak cortisol (p <0.025), reduced cortisol AUC (p <0.005) and longer time to peak cortisol (p <0.05). Abnormalities were seen in both sexes but were more pronounced in females. Unstimulated adrenal androgen and 17-hydroxyprogesterone concentrations were normal. CONCLUSIONS: Adolescents with CFS have subtle alterations in adrenal function suggesting a reduction in central stimulation of the adrenal glands. The more pronounced effects in females may reflect differential central effects of stress on hypothalamic-pituitary-adrenal axis regulation between the sexes.

Enhancement of growth hormone bioactivity by zinc in the eluted stain assay system.

The effects of ionic zinc (Zn2+) on human (h) GH bioactivity have been examined using a lactogenic bioassay. The potencies of pituitary-derived hGH (IRP 80/505), recombinant 22K hGH (IRP 88/624), pituitary-derived human PRL (IRP 84/500), and a recombinant methionyl 20-kilodalton variant of hGH in the presence of selected concentrations of ZnCl2 were investigated with an eluted stain assay that uses Nb2 rat lymphoma cells. This precise colorimetric bioassay is based upon the reduction of a yellow tetrazolium salt, 3-[4,5-dimethyl-thiazol-2-yl]2,5-di-phenyl-tetrazolium bromide, to its purple formazan by lactogen-activated Nb2 cells. Zinc (6-100 microM) enhanced the bioactivity of low doses (< 0.045 nM) of both pituitary-derived and recombinant 22K hGH, although the magnitude of enhancement was considerably less than might have been anticipated from previous binding studies (13). Higher concentrations of pituitary-derived hGH (> 0.045 nM) were inhibited by Zn2+. The bioactivity of recombinant methionyl 20K hGH was greatly enhanced by zinc (3-100 microM). In contrast to hGH, the bioactivity of hPRL was not potentiated by Zn2+. These discriminatory effects of Zn2+ when stimulating via the lactogenic receptor are in concordance with the results of previous radioligand binding studies (13). The striking enhancement of 20K hGH lactogenic bioactivity was observed at Zn2+ concentrations within the physiological range for normal human serum (5-20 microM).

Hexarelin-induced growth hormone, cortisol, and prolactin release: a dose-response study.

Dose-response data for GH-releasing peptides are limited. We studied the effects of varying doses (0-1.0 microgram/kg) of hexarelin, a novel GH-releasing peptide, administered iv to healthy adult males on GH, PRL, and cortisol release. In addition, we studied the effect of administration of a single dose of GHRH-(1-29)-NH2 (1.0 microgram/kg), alone or in combination with a low dose of hexarelin (0.125 microgram/kg). Dose-response curves for the maximum GH response and maximum percent change in serum PRL and cortisol concentrations from baseline were constructed. The GH dose-response curve reached a plateau of 140 mU/L, corresponding to a hexarelin dose of 1.0 microgram/kg, with an ED50 of 0.48 +/- 0.02 microgram/kg (mean +/- SEM). The PRL dose-response curve reached a plateau of 180% for the maximum percent rise from baseline, corresponding to a hexarelin dose of 1.0 microgram/kg, with an ED50 of 0.39 +/- 0.02 microgram/kg. The cortisol dose-response curve showed a step increase to approximately 40% at a hexarelin dose of 0.5 microgram/kg. The coadministration of GHRH-(1-29)-NH2 (1.0 microgram/kg) and low dose hexarelin (0.125 microgram/kg) resulted in massive GH release (115 +/- 32.8 mU/L), a moderate rise in serum PRL (84.9 +/- 27.5%), and no rise in serum cortisol. These data show that iv hexarelin was capable of inducing GH, PRL, and cortisol release in a dose-dependent manner. Low dose hexarelin was synergistic with GHRH and potent for GH release with a minimal effect on other hormones.

Congenital adrenal hyperplasia due to 21-hydroxylase deficiency: alterations in cortisol pharmacokinetics at puberty.

In congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency, treatment with glucocorticoid and mineralocorticoid substitution is not always satisfactory. Suboptimal control is often observed in pubertal patients, despite adequate replacement doses and adherence to treatment. We investigated whether the pubertal process is associated with alterations in cortisol pharmacokinetics resulting in a loss of control of the hypothalamic-pituitary-adrenal axis. We determined the pharmacokinetics of hydrocortisone administered iv as a bolus. A dose of 15 mg/m(2) body surface area was given to 14 prepubertal (median age, 9.4 yr; range, 6.1--10.8 yr), 20 pubertal (median, 13.5 yr; range, 10.6--16.8 yr), and 6 postpubertal (median, 18.2 yr; range, 17.2--20.3 yr) patients with salt-wasting CAH. All patients were on standard replacement therapy with hydrocortisone and 9 alpha-fludrocortisone. Serum total cortisol concentrations were measured at 10-min intervals for 6 h following iv hydrocortisone bolus and analyzed using a solid-phase RIA. The serum total cortisol clearance curve was monoexponential. Mean clearance was significantly higher in the pubertal group (mean, 427.0 mL/min; SD, 133.4) compared with the prepubertal (mean, 248.7 mL/min; SD, 100.6) and postpubertal (mean, 292.4 mL/min; SD, 106.3) (one-way ANOVA, F = 9.8, P < 0.001) groups. This effect persisted after adjustment for body mass index. The mean volume of distribution was also significantly higher in the pubertal (mean, 49.5 L; SD, 12.2) than the prepubertal (mean, 27.1 L; SD, 8.4) patients but not in the postpubertal (mean, 40.8 L; SD, 16) (ANOVA, F = 15.2, P < 0.001) patients. The significance remained after correction for body mass index. There was no significant difference in mean half-life of total cortisol in prepubertal (mean, 80.2 min; SD, 19.4), pubertal (mean, 84.4 min; SD, 24.9), and postpubertal (mean, 96.7 min; SD, 9.9) patients. Similar differences between groups were observed when the pharmacokinetic parameters of free cortisol were examined. In addition, the half-life of free cortisol was significantly shorter in females compared with males (P = 0.04). These data suggest that puberty is associated with alterations in cortisol pharmacokinetics resulting in increased clearance and volume of distribution with no change in half-life. These alterations probably reflect changes in the endocrine milieu at puberty and may have implications for therapy of CAH and other conditions requiring cortisol substitution in the adolescent years.

The effect of changing gonadotropin-releasing hormone pulse frequency on puberty.

We have examined the effect of using different pulse frequencies of exogenous GnRH to induce puberty and the time relationship among LH, FSH, sex steroids, and GH in these individuals. Five girls and three boys with delayed puberty received exogenous GnRH at either 3-h frequency (slow) or every 45 min (fast). Treatment was initially given overnight and increased to 24 h when breast stage 3 in girls or testicular volume of 10 mL in boys was attained. Twenty-four-hour gonadotropin profiles were performed after 5 days, 1 month, 3 months, 6 months, and 1 yr of treatment. Temporal relationships among LH, FSH, and estradiol; LH and testosterone; GH and estradiol; and GH and testosterone were examined by cross-correlation. There was no difference in the rate of pubertal progress between the groups. Mean serum gonadotropin and sex steroid levels did not differ. LH was correlated with estradiol for both groups at 240 min (slow group, r = 0.54; fast group, r = 0.50). Estradiol correlated with LH at 300 min in the slow group (r = -0.41) and 200 min in the fast group (r = -0.37). FSH correlated with estradiol at 140 min in the slow group (r = 0.62) and 160 min in the fast group (r = 0.50). A rise in estradiol occurred 140-160 min after a rise in FSH and 240 min after a rise in LH. A rise in estradiol was followed 200-300 min later by a fall in LH. LH was correlated with testosterone at 60 min in the slow group (r = 0.73) and at 40 min in the fast group (r = 0.55). Testosterone correlated with LH at 420 min in the slow (r = -0.67) and 460 min in the fast group (r = -0.40). A rise in LH was followed 40-60 min later by a rise in testosterone. A rise in testosterone was followed by fall in LH 420-460 min later. GH correlated with estradiol at 320 min in the slow group (r = 0.37) and 380 min in the fast group (r = 0.38). A rise in GH was followed, after 320-380 min, by a rise in estradiol. There was a correlation between GH and testosterone in the slow group after 280 min (r = 0.44). A rise in GH was followed by a rise in testosterone after 280 min. The pituitary-gonadal axis is sufficiently robust to allow puberty to progress with different fixed pulse frequencies. There is a temporal relationship among LH, FSH, and estradiol secretion and between LH and testosterone secretion. We have demonstrated the feedback effect of sex steroids at the level of the pituitary and the time course of the effect of GH on gonadal function.

The measurement of growth hormone bioactivity in patient serum using an eluted stain assay.

We have adapted the MTT-ESTA bioassay for human GH (hGH) to measure the lactogenic bioactivity of the hormone in human serum. This highly quantitative in vitro colorimetric bioassay is based upon the reduction of a tetrazolium salt, 3-[4,5-dimethyl-thiazol-2-yl]2,5-diphenyl tetrazolium bromide (MTT), to its formazan by lactogen-activated Nb2 cells. Relatively high concentrations of human serum (1-10%) modified responses to the hormone in a complex manner. As the serum effects varied between samples, it proved impossible to adapt the bioassay by the conventional approach of using a lactogen-depleted serum as a representative matrix. However, as the Nb2 cells were exceptionally sensitive to hGH, the serum effects could be diluted out. We adopted a dilution strategy by which all samples of human serum were included in the bioassay at a concentration of 0.625% or less. A valid assay was obtained, as judged by the criteria of parallelism between diluted samples and hGH standards, and recoveries of spiked samples that were close to 100%. Hormonal specificity was achieved with the use of a highly specific anti-PRL antiserum. A within-assay precision of between 2-5% over the dose range of 0.03-0.96 microgram hGH/L was attained. As only highly diluted samples could be used, the sensitivity of the clinical bioassay was 1.2-2.4 micrograms hGH/L. The between-assay precision was estimated to be 11% and 9% at initial hGH concentrations in serum of 4.8 and 19.2 micrograms hGH/L, respectively. By exploiting the high sample capacity of the eluted stain bioassay system, we followed the changes in bioactivity and immunoactivity of hGH in multiple timed samples after stimulation of hGH secretion in an adult by GHRH. Systematic and progressive changes were observed in the bioactive/immunoactive ratios. Analogous changes were observed after insulin-induced hypoglycemia in a child with short stature. We speculate that the changes in the bioactive/immunoactive ratios reflect alterations in the proportions of the isoforms of hGH in the circulation after acute stimulation.

The effect of changing somatostatin tone on the pituitary growth hormone and thyroid-stimulating hormone responses to their respective releasing factor stimuli.

Somatostatin (SS) inhibits GH and TSH secretion, but its role in modulating their pulsatility is unclear. We studied GH and TSH responses to GH-releasing hormone (GHRH) and TRH stimulation upon a variable background infusion of saline, SS-(1-14) at 20 and 100 micrograms/m2.h, and oral pyridostigmine (30 and 60 mg) in six adult males. Basal GH levels were unaffected by SS-(1-14). Deconvolution analysis of serum GH values demonstrated that the pituitary responded to two GHRH stimuli 90 min apart without attenuation of the second response. The higher dose of SS-(1-14) significantly blunted the first GH response; second GH responses were further attenuated by both SS-(1-14) doses. Maximum GH release and "switch-off" rates for both stimuli were reduced without changes in the 50% secretion time. Pyridostigmine enhanced the first GH response to GHRH with an increase in the GH release rate; second GH responses were not augmented. GH secretion was prolonged by pyridostigmine, although the 50% secretion time remained unchanged. Peak stimulated serum TSH was attenuated by both SS-(1-14) doses, but pyridostigmine had no effect. All other TSH parameters examined were unaffected. We conclude that the GH response to GHRH is dependent on SS tone, but that the thyrotroph is not tonically inhibited by SS. SS attenuates the rate of GH release without changing the duration of secretion and appears important in terminating GH secretion.

Peak and trough growth hormone concentrations have different associations with the insulin-like growth factor axis, body composition, and metabolic parameters.

GH is secreted in a pulsatile fashion, promoting growth and anabolism. The components of the pulsatile signal involved in these diverse effects are unclear. We constructed (20-min sampling interval) and analyzed 24-h serum GH profiles in 45 adult male volunteers, 59.4-69.9 yr old, body mass index (BMI) 21.9-36.5 Kg/m2, using Fourier transformation and a concentration distribution analysis that determines the concentration at or below which the serum GH concentrations in the 24-h profile spend a percentage of the total time. The observed concentrations (OC) below which 95% and 5% of the values in the time series lie [lsb]OC95 (peaks) and OC5 (troughs)] and mean 24-h serum GH concentrations were related to measures of the insulin-like growth factor (IGF) family, parameters of body composition, fasting insulin and cholesterol measures, and GH-binding protein concentrations. Mean 24-h serum GH concentrations ranged between 0.19 and 2.15 mU/L (1 microgram/L = 2.6 mU/L). Pulse periodicity was between 180 and 200 min. There was a positive relationship between peak GH levels and serum IGF-1 and IGFBP-3 levels (r = 0.39; P = 0.009 and r = 0.32; P = 0.03, respectively). GH trough levels were unrelated to these measures of the IGF family. In contrast, GH troughs were related inversely to BMI (r = -0.31; P = 0.04) and waist-hip ratio (r = -0.4; P = 0.006). Peak GH levels were not related to these measures. Factors known to influence these measures, fasting insulin concentration, or cortisol secretion did not alter the trough GH relationship in multiple regression analysis. All GH parameters were related inversely to fasting insulin concentration. Although GH parameters were related inversely to cholesterol and low-density lipoprotein-cholesterol, this effect disappeared when age and fasting insulin levels were introduced into the regression. GH-binding protein levels related most strongly to BMI (r = 0.60; P < 0.001), with no effect of any GH parameter observed in multiple regression analysis. These results suggest that the peak values of a GH concentration profile may influence the IGF axis, whereas trough values may influence body composition and metabolic parameters of GH action.