GH Sampling Research Articles

Abstract P301: Preeclampsia and Gestational Hypertension: Does sEng Levels Make the Important Difference Preeclampsia and Gestational Hypertension: Does sEng Levels Make the Important Difference

The origin of Preeclampsia (PE), a multi-systemic disorder of pregnancy, lies to a great extent on the balance of the anti-angiogenic and angiogenic proteins during pregnancy. In the present study, we have determined the levels of sFlt-1 and sEng levels (anti-angiogenic protein) and Placental Growth Factor, PlGF (angiogenic Protein) in the serum of the patients with hypertensive disorder of pregnancy (including Gestational Hypertension, GH and PE) and Normotensive (NT) pregnancy. The levels of sFlt-1 were found to be significantly higher in the 3 rd trimester and at term in the hypertensive pregnancy (GH and PE), compared to the NT pregnancy, (8.67±1.93 ng/ml, n=13 vs. 3.95±.37 ng/ml, n=111 at the 3rd trimester and 14.90±2.68 ng/ml, n=15 vs. 6.58±.42 ng/ml, n=111 at term). The levels of sFlt-1 were considerably higher in the PE samples compared to the GH samples, but not significant. Similarly the levels of sEng were found to be significantly higher in the 3 rd trimester and at term in the hypertensive pregnancy (GH and PE), compared to the NT pregnancy (11.18±1.51 ng/ml, n=15 vs. 7.86±.25 ng/ml, n=106 at the 3 rd trimester and 12.68±1.70 ng/ml, n=14 vs. 10.01±.42 ng/ml, n=106 at the term). The levels of sEng were, however, found to be significantly higher in all the trimester and at term in the PE samples compared to the NT Samples ( 6.49±1.14 ng/ml, n=7 vs 4.21±.28 ng/ml, n=106, 6.89±2.30 ng/ml, n=7 vs. 3.76±.25 ng/ml, n=106, 13.10±2.12 ng/ml, n=7 vs. 7.86±.37 ng/ml, n=106, 14.93±2.27 ng/ml, n=7, vs. 10.01±.42 ng/ml, n=106 at the 1 st , 2 nd , 3 rd trimesters and term respectively), but not in the GH samples. The angiogenic protein, PlGF was found to be significantly lower in the hypertensive conditions of pregnancy (PE and GH) samples compared to the NT samples, only in the 3 rd trimester (440±48.58 pg/ml, n=15 vs 1278±104 pg/ml, n=119), although its levels were considerably decreased in the 2 nd trimester and at term, but not significant. Within the hypertensive conditions of pregnancy, the blood pressure increase at term was more in the PE patients compared to the GH patients (42±5.1/25±3.3 mm Hg vs. 18±3.7/13±3.3 mm Hg, p<0.05 ) compared to the BP recorded at the 1 st trimester. The results of the present study indicate a more potent role of sEng in the development of PE.

Endogenous Estrogen Regulates Somatostatin-Induced Rebound GH Secretion in Postmenopausal Women.

Systemic concentrations of T, estradiol (E2), GH, IGF-1, and IGF binding protein-3 decline in healthy aging individuals. Conversely, T and E2 stimulate GH and IGF-1 production in hypogonadal patients. Because E2 stimulates GH secretion, putatively via the nuclear estrogen receptor-α and E2 and GH fall with menopause, we postulated that diminished endogenous E2 contributes to low GH output in older women. The study was conducted at the Mayo Center for Clinical and Translational Science. This was a randomized, double-blind, controlled study in 60 healthy postmenopausal women treated with the following: 1) double placebo; 2) anastrozole, a potent inhibitor of aromatase-enzyme activity, which mediates E2 synthesis from T; and/or 3) fulvestrant, a selective estrogen receptor-α antagonist. GH pulse generation was quantified by frequent GH sampling before and after short-term iv somatostatin infusion, thought to induce hypothalamic GHRH-mediated rebound-like GH secretion. On anastrozole, E2 fell from 3.1 ± 0.35 pg/mL to 0.36 ± 0.04 pg/mL, and estrone from 13 ± 1.4 pg/mL to 1.9 ± 0.01 pg/mL (P < .001) by mass spectrometry. Estrogen values were unchanged by fulvestrant. T concentrations did not change. One-hour peak GH rebound after somatostatin infusion declined markedly during both estrogen-deprivation schedules (P < .001). Mean (150 min) maximal GH rebound decreased comparably (P < .001). Measures of GH rebound correlated negatively with computed tomography-estimated abdominal visceral fat (all P < .05). These data suggest a previously unrecognized dependence of hypothalamo-pituitary GH regulation on low levels of endogenous estrogen after menopause.

The Clinical Utility of TIMP3 Expression in ACTH-Secreting Pituitary Tumor.

In recent years, the tissue inhibitor of metalloproteinase-3 (TIMP3) plays a pivotal role in tumorigenesis, while the role of TIMP3 in adrenocorticotrophic hormone (ACTH)-secreting pituitary adenomas remains unclear. In this study, 86 sporadic pituitary tumor specimens, including ACTH (40), GH (18), PRL-secreting (8), and non-functioining (20) and non-tumorous pituitary samples (n = 10) were available, and then, the mRNA and protein expression of TIMP3 was quantified by quantitative reverse transcriptase polymerase chain reaction (RT-PCR), western blotting, and immunohistochemistry, respectively. Our findings showed that TIMP3 expression was significantly correlated with Ki-67 expression and the invasiveness of pituitary adenomas. TIMP3 mRNA and protein expression were reduced in ACTH-secreting pituitary adenomas and the other three types of pituitary adenomas compared to adjacent non-tumorous pituitary tissues (all p < .01). On the other hand, the expression of TIMP3 was negatively correlated with tumor size and Ki-67 in ACTH-secreting pituitary adenomas. TIMP3 mRNA expression was significantly lower in invasive pituitary adenomas than that in noninvasive ones (1.92-fold, p < .05). TIMP3 protein levels were also significantly lower in the majority of invasive adenomas (1.41-fold, p < .05) Furthermore, TIMP3 mRNA and protein expression were significantly lower in pituitary giant adenomas than those in microadenomas (2.58-fold, p < .05). In conclusion, the expression of TIMP3 is low in pituitary adenomas including ACTH-secreting pituitary adenomas and negatively associated with tumor aggressiveness. TIMPs may play a potential role in the progression of ACTH-secreting pituitary adenomas and be useful as a biomarker of invasiveness.

PS1-36: Developing Rapid Molecular E.coli Clonal Diagnostics for Community Laboratory Settings

Background/Aims E.coli infections of the urinary tract (UTI) are among the most common infections worldwide. U.S. costs of UTI care are >$1B annually. Recently, there has been rapid worldwide emergence of resistant E.coli, which increases the percentage of serious events and the difficulty of care. One contributing factor may be that usual care typically involves presumptive antibiotic treatment, with antimicrobial sensitivity results available only after 1–2 days. Inappropriate treatment during that interval is suboptimal for the patient and facilitates E.coli resistance. We conducted a 1-year pilot of a potential new diagnostic technology to test for E.coli infection at the clonal level by: 1) optimizing PCR methods to directly and rapidly test urine samples for two E.coli sub-strains (clones) in a community lab setting (Group Health [GH]); 2) using this method to identify two highly-resistant sub-strains in GH samples; and 3) comparing usual care prescribing patterns to potential prescribing based on sub-strain results, focusing on the “drug-bug mismatch”.

Reprimo (RPRM) Is a Novel Tumor Suppressor in Pituitary Tumors and Regulates Survival, Proliferation, and Tumorigenicity

Reprimo (RPRM), initially identified as a downstream effector of p53-induced cell cycle arrest at G(2)/M, is a putative tumor suppressor silenced in some types of cancer. In microarrays, the RPRM transcript was repressed 26-fold in gonadotrope (null cell) human pituitary tumors compared with normal pituitary but in the absence of changes in p53. Inhibition of RPRM mRNA was confirmed by RT-PCR in all gonadotrope tumors, most GH samples, and variably in other tumor types. Human pituitary tumors showed no evidence of abnormal promoter hypermethylation as a mechanism of RPRM repression. RPRM stable expression in gonadotrope (LβT2) and GH (GH3) pituitary cells resulted in decreased rates of cell proliferation by 55 and 30%, respectively; however, RPRM reexpression did not alter G(2)/M transition. In addition, RPRM increased rates of apoptosis in response to growth factor deprivation as assessed by caspase-3 cleavage and nuclear condensation. Clonagenic assays showed a 5.3- and 3.7-fold suppression of colony growth in RPRM-overexpressing LβT2 and GH3 cells, respectively, supporting its role as a tumor suppressor. In cells stably expressing RPRM mRNA, protein levels were actively suppressed due to rapid degradation through ubiquitination and proteasomal targeting. Growth factor withdrawal, as a model of cellular stress, stabilized RPRM protein levels. Together these data suggest that RPRM is transiently up-regulated at a posttranscriptional level in times of cellular stress to restrict cell survival, proliferation, and tumor formation. When RPRM is silenced as in human pituitary tumors, unrestrained growth and tumor progression may occur.

Human Cytomegalovirus Glycoprotein Genotypes in the Genital Tract Tissue of Tubal Pregnancy Patients

This study investigated human cytomegalovirus (HCMV) glycoprotein genotypes in the genital tract tissue of 125 tubal pregnancy patients. The HCMV glycoprotein-B N-terminus (gBn, 54 - 485 NT), gB endoprotease cleavage site (gBclv, 1284 - 1600 NT) and glycoproteinH (gH, -58 - 213 NT) gene fragments were amplified by nested polymerase chain reaction and sequenced to identify gB and gH genotypes. Of 16 gBn-positive samples, four were gBn1, one was gBn2 and 11 were the gBn3 genotype. Of 13 positive gBclv samples, seven were gBclv1, two were gBclv2 and four were the gBclv3 genotype. Of 20 positive gH samples, 10 were gH1, six were gH2 and four were a combined gH1/gH2 genotype. In 10 of the samples that were positive for the gBn and gBclv genotypes, the gBn and gBclv genotypes were not consistent (four were gBclv1-gBn3). This study showed that: (i) HCMV infection with the gB1 - gB3 glycoprotein genotypes is present in tubal pregnancy; (ii) the gBclv and gBn genotypes are not strictly consistent; and (iii) intragenetic variability within the gB gene due to homologous recombination occurs frequently.

Emulsifying and foaming properties of transglutaminase-treated wheat gluten hydrolysate as influenced by pH, temperature and salt

Hydrolyzed wheat gluten (GH, 77–85% protein) was prepared by limited hydrolysis with chymotrypsin at 37 °C for 4 h (degree of hydrolysis=6.4%) and 15 h (degree of hydrolysis=10.3%). The effect of microbial transglutaminase (MTGase) treatment (55 °C for 1 h, or 5 °C for 18 h) on the emulsifying and foaming properties of GH was evaluated under selected food processing conditions (pH 4.0 and 6.5, 0 and 0.6 M NaCl, and temperature 20 and 5 °C). At pH 4.0 and 0 M NaCl the MTGase treatment substantially increased foaming capacity (FC) of GH compared with their respective control GH samples, as a result of enhanced peptide adsorption to the air–water interface, but FC was similar for both control and MTGase-treated GH at pH 6.5. In contrast, foam drainage stability (FS) of MTGase-treated GH decreased at pH 4.0, but increased significantly ( P<0.05) at pH 6.5 when compared with their respective control GH samples. The FC and FS were affected by 0.6 M NaCl in a pH-dependent manner. The MTGase treatments increased emulsion activity index up to 15-fold at pH 6.5, while emulsion stability index was influenced by emulsion temperature and ionic strength conditions. The MTGase-induced changes in functional properties of GH were attributed to pH-dependent solubility changes, the amphiphilic nature of gluten peptides and increased electrostatic repulsion resulting from deamidation.

Assessment of the Magnitude of Growth Hormone Hypersecretion in Active Acromegaly: Reliability of Different Sampling Models

The pulsatility of GH secretion in acromegaly poses difficulty in ascertaining true daily GH milieu in patients with this disease. Intensive GH sampling [every 10-20 (Q10-20) min for 24 h] is not practical in clinical practice. Our objective was to ascertain reliability of abbreviated sampling protocols to reflect true 24-h mean GH concentrations in patients with acromegaly. An analysis of previously obtained plasma GH profiles was performed. The analysis was performed at the General Clinical Research Center at the University of Michigan. A total of 115 GH profiles obtained in 94 patients with active acromegaly were examined. Frequent blood sampling, i.e. Q10-20 min for 24 h, was performed. Concordance of 24-h mean GH concentrations derived from Q10- to 20-min samplings with abbreviated GH sampling schedules was performed. The study was planned after data collection. All abbreviated schedules of GH sampling correlated well with the true 24-h plasma GH means (i.e. Q10- to 20-min sampling) (R = 0.93-0.98; P < 0.0001 for all). In the GH range more than 20 microg/liter, only 5 and 9-h means had R values more than 0.9. Single GH concentrations less than 1 microg/liter had a positive predictive value of only 0.29, and those with less than 2.5 microg/liter had a positive predictive value of 0.67 vs. their corresponding 24-h mean GH values of the same magnitude. The intensity of GH sampling in patients with acromegaly may vary depending on the nature of the required information. Investigators and clinicians should be aware of the limitations of the abbreviated GH sampling protocols in acromegaly.

Evaluation of Short Stature, Carbohydrate Metabolism and Other Endocrinopathies in Bloom’s Syndrome

Aims: To obtain an understanding of the etiology of proportional dwarfism and endocrinopathies of Bloom’s syndrome (BS). Methods: Admission for 5-day periods to an NIH-supported Clinical Research Center of a randomly selected population of persons with BS (n = 11; mean age 11.5 years, range 9 months to 28.5 years) for clinical and genetic history-taking, physical examination, and endocrinological, gastroenterological and immunological testing. Results: An oral glucose tolerance test was performed in all participants. Impaired glucose tolerance was present in 4 individuals, insulin resistance was observed in 6 individuals, and previously unrecognized diabetes was found in 1. Growth hormone provocation was normal in the 10 individuals tested. Overnight frequent GH sampling was suggestive of neurosecretory dysfunction in 3. Compensated hypothyroidism was found in 2 participants. Lipid profile abnormalities were present in 5 of 10 individuals. Low immunoglobulin concentrations (IgG and/or IgM) were seen in all tested. Intestinal absorption by D-xylose and/or fecal fat measurement was normal in all individuals tested as well. Conclusion: Altered carbohydrate metabolism is very common in BS, and is present from childhood. BS dwarfism is not related to growth hormone deficiency or malabsorption. The basis for the growth restriction in BS remains to be elucidated.

Blockade of endogenous growth hormone-releasing hormone receptors dissociates nocturnal growth hormone secretion and slow-wave sleep

A temporal association between non-rapid eye movement (NREM) sleep stages 3 and 4 and nocturnal augmentation of GH release was found long ago, yet the precise mechanism for this association has not been identified. It has been shown, however that pulsatile GHRH administration increases both slow-wave sleep (SWS) and GH. Based on these data, a role for GHRH as an inducer of SWS was proposed. To test this hypothesis, we have performed the corollary experiment whereby the action of endogenous GHRH has been antagonized. Healthy men (20-33 years old) had an infusion of GHRH antagonist ((N-Ac-Tyr(1), D-Arg(2)) GHRH-29 (NH(2))) or saline for a 12-h period, between 2100 and 0900 h. An i.v. bolus of GHRH was given at 0700 h and GH samples were drawn from 0700 to 0900 h to document the efficacy of GH suppression by the GHRH antagonist. A limited montage sleep study was recorded from 2300 to 0700 h during each admission. Plasma GH concentrations were analyzed by the use of a sensitive chemiluminometric assay. Effectiveness of the GHRH antagonist was validated in all subjects by demonstrating 93+/-1.8% (P=0.012) suppression of GH response to a GHRH bolus. Polysomnography demonstrated that the percentage of SWS was not different when saline and GHRH antagonist nights were compared (P=0.607); other quantifiable sleep parameters were also unchanged. We conclude that endogenous GHRH is indispensable for the nocturnal augmentation of GH secretion, but that it is unlikely to participate in the genesis of SWS.

Significance of "abnormal" nadir growth hormone levels after oral glucose in postoperative patients with acromegaly in remission with normal insulin-like growth factor-I levels.

Our initial study in postoperative patients with acromegaly identified a group of patients in remission, as defined by normal IGF-I levels, but who had a subtle abnormality of GH suppression after oral glucose. To investigate the significance of this abnormality, we have undertaken further detailed testing of GH secretion and a longitudinal follow-up of some of these patients. Of the 110 postoperative patients with acromegaly evaluated by oral glucose tolerance test, 76 were in remission (i.e. normal IGF-I level), and of these subjects with acromegaly in remission, 50 had normal nadir GH (<0.14 microg/ml) (group I), and 26 had abnormal nadir GH (>0.14 microg/ml) (group II). Fourteen subjects in remission, seven from remission group I and seven from remission group II, underwent additional testing consisting of both hourly GH sampling over 8 h and, on a separate day, arginine stimulation testing. The mean of hourly GH was higher in group II (0.47 +/- 0.04 microg/liter) than in group I (0.19 +/- 0.07 microg/liter; P = 0.002). GH response to arginine was greater in group II than in group I (P < 0.01). Of those patients in remission from the initial cohort studied, 49 (30 subjects from group I and 19 from group II) underwent serial longitudinal oral glucose tolerance testing every 1-2 yr over a 1- to 6.5-yr period (mean follow-up, 3.2 yr). The initial pattern of GH suppression persisted in most patients. IGF-I levels remained normal in all patients in group II, but five subjects from group II developed an elevated IGF-I level and, thus, a biochemical recurrence. The rate of disease recurrence was greater in group II than in group I (P = 0.003). We have found that some postoperative subjects with acromegaly in remission with normal IGF-I levels have persistently abnormal nadir GH levels after oral glucose that may be accompanied by other evidence of greater GH secretion than postoperative patients with normal GH suppression. This abnormal pattern of GH suppression may be associated with increased risk of disease recurrence in some patients.

Gender-, age-, body composition- and training workload-dependent differences of GH response to a discipline-specific training session in elite athletes: a study on the field.

Ninety-nine Italian elite athletes (61 M, 38 F, mean age +/- SE: 24.1 +/- 0.6 yr, age range: 17-47 yr) of different disciplines volunteered to participate in this investigation. Basal GH concentrations were significantly higher (p<0.0001) in females (6.2 +/- 1.1 ng/ml) vs males (1.9 +/- 0.5 ng/ml). Basal GH values were negatively correlated with age and body mass index (BMI); no significant correlation was found between GH and IGF-I levels. Among female athletes, 8/38 had basal GH values higher than 10 ng/ml [2/8 athletes were taking oral contraceptives (OC)], while among males 6/61 had values higher than 5 ng/ml. In females, training sessions significantly increased (p<0.0001) basal GH concentrations (peak GH: 18.5 +/- 1.9 ng/ml), while in males GH responses were lower than in females (11.8 +/- 1.4 ng/ml, vs F: p<0.005). Six out of 38 female and 6/61 male athletes were considered GH hypo-responders (i.e. negative difference between peak GH and basal GH values), the large majority of them being subjects with elevated basal GH concentrations. In responsive athletes, peak GH values occurred immediately at the end of the training session both in males and in females; GH concentrations rapidly declined during recovery. No significant correlations were found between peak GH and age, body weight and BMI in either gender. GH responses were directly related (p<0.001) to the intensity of the workload during the sessions. In conclusion, the present study demonstrates that: 1) some elite athletes had increased GH concentrations before training, which were however associated with normal IGF-I levels; 2) GH peaks after a discipline-specific training session were significantly higher in females than in males performing the same discipline, gender-related differences disappearing when post-exercise total GH outputs (area under the curve) were compared; 3) peak GH values were directly correlated with training workload; 4) GH concentrations rapidly declined during recovery, values at the end of the post-training GH sampling being generally lower than those found in basal condition.

Effects of growth hormone secretion on body composition in patients with Crohn's disease.

Crohn's disease is a multisystem disorder characterized by chronic intestinal inflammation. Accumulation of mesenteric fat occurs in patients with Crohn's disease, although the mechanisms underlying site-specific changes in adipose deposition are unclear. To investigate whether there are alterations in site-specific adipose deposition in patients with Crohn's disease and to determine hormonal influences that may underlie such changes, we investigated body composition and serum hormone levels in 20 men with Crohn's disease (mean age, 45 +/- 2 yr) and 20 age-, gender-, and body mass index-matched normal controls (mean age, 43 +/- 3 yr). None of the Crohn's patients was receiving glucocorticoid therapy. Subjects underwent hourly GH sampling for 12 h beginning at 2000 h and fasting serum IGF-I and testosterone measurements. Body composition was assessed by quantitative computed tomography of the abdomen and bioelectrical impedance analysis. In the Crohn's disease and control subjects, mean serum GH levels were 1.07 +/- 0.2 and 1.7 +/- 0.2 ng/ml (P = 0.06), serum IGF-I levels were 162.7 +/- 10.5 and 194.8 +/- 15.7 ng/ml (P = 0.1), and serum testosterone levels were 489 +/- 33 and 514 +/- 38 ng/ml (P = NS), respectively. Percentage body fat was significantly higher in the Crohn's patients (21 +/- 0.8% vs. 17.7 +/- 0.9%, respectively; P = 0.013). Intraabdominal fat (IAF) was significantly higher in the Crohn's subjects vs. controls (115 +/- 11 vs. 69 +/- 7 cm(2), respectively; P = 0.001). The ratio of intraabdominal to total body fat was higher in the Crohn's subjects than in the controls (0.4 +/- 0.1 vs. 0.3 +/- 0.1, respectively; P = 0.025). Subcutaneous fat area was similar in the two groups. IAF was higher in Crohn's patients even when controlling for testosterone and mean serum GH. Mean serum GH contributed independently to the differences in IAF (P = 0.001). The ratio of IAF to total body fat remained higher in the Crohn's subjects when controlling for serum testosterone, but was no longer significant in a model that also included IGF-I and mean serum GH. GH levels contributed independently to the differences in the intraabdominal to total body fat ratio (P = 0.02). In the Crohn's patients, serum GH correlated negatively with intraabdominal and total body fat and the ratio of intraabdominal to total body fat. Crohn's disease is associated with an increase in central fat accumulation, with more IAF and a higher ratio of intraabdominal to total body fat compared with controls. Although serum GH levels were similar in the two groups, GH contributed significantly to the abdominal fat measurements. These data show that GH has an important role in modulating visceral fat distribution in patients with Crohn's disease.

Characterization of gsp-mediated growth hormone excess in the context of McCune-Albright syndrome.

McCune-Albright syndrome (MAS) is a disorder characterized by the triad of café-au-lait skin pigmentation, polyostotic fibrous dysplasia of bone, and hyperfunctioning endocrinopathies, including GH excess. The molecular etiology of the disease is postzygotic activating mutations of the GNAS1 gene product, G(s)alpha. The term gsp oncogene has been assigned to these mutations due to their association with certain neoplasms. The aim of this study was to estimate the prevalence of GH excess in MAS, characterize the clinical and endocrine manifestations, and describe the response to treatment. Fifty-eight patients with MAS were screened, and 22 with stigmata of acromegaly and/or elevated GH or IGF-I underwent oral glucose tolerance testing. Twelve patients (21%) had GH excess, based on failure to suppress serum GH on oral glucose tolerance test, and underwent a TRH test, serial GH sampling from 2000-0800 h, and magnetic resonance imaging of the sella. We found that vision and hearing deficits were more common in patients with GH excess (4 of 12, 33%) than those without (2 of 56, 4%). Of interest, patients with a history of precocious puberty and GH excess who had reached skeletal maturity achieved normal adult height despite a history of early epiphyseal fusion. All 9 patients tested had an increase in serum GH after TRH, 11 of 12 (92%) had hyperprolactinemia, and all 8 tested had detectable or elevated nighttime GH levels. Pituitary adenoma was detected in 4 of 12 (33%) patients. All patients with elevated IGF-I levels were treated with cabergoline (7 patients), long-acting octreotide (LAO; 8 patients), or a combination of cabergoline and LAO (4 patients). In six of the seven patients (86%) treated with cabergoline, serum IGF-I decreased, but not to the normal range. In the eight patients treated with LAO alone, IGF-I decreased, and, in four, returned to the normal range. The remaining 4 patients were treated with a combination of cabergoline and LAO. For them, symptoms of GH excess diminished, and IGF-I decreased further, but did not enter the normal range. GH excess is common in MAS and results in a distinct clinical phenotype characterized by inappropriately normal stature, TRH responsiveness, prolactin cosecretion, small or absent pituitary tumors, a consistent but inadequate response to treatment with cabergoline, and an intermediate response to LAO.

Effect of spontaneous GH secretion and the GH sampling period on the accuracy of models for predicting growth responses to GH treatment.

Effect of spontaneous GH secretion and the GH sampling period on the accuracy of models for predicting growth responses to GH treatment.

Effect of Spontaneous GH Secretion and the GH Sampling Period on the Accuracy of Models for Predicting Growth Responses to GH Treatment

Effect of Spontaneous GH Secretion and the GH Sampling Period on the Accuracy of Models for Predicting Growth Responses to GH Treatment

Growth hormone secretory dynamics over the menstrual cycle.

Whether GH secretion in women varies over the menstrual cycle is uncertain. Previous investigations have led to conflicting conclusions; some studies suggested that there is an estrogen mediated rise in GH during the periovulatory (PO) and luteal (L) phases whereas others indicated no change in GH axis over the cycle. Differences in conclusions could relate to heterogeneity of the study populations, GH sampling paradigms or sensitivity of the GH assays used. In order to investigate whether GH secretion varied over the cycle, 24-h GH profiles using every 10-min sampling were obtained in 6 ovulatory women during the early follicular (EF), PO and L phases of the cycle. The TSH response to TRH, GH response to GRH and fasting plasma IGF-I were measured on each occasion. There was a trend toward higher integrated GH concentration (IGHC) during the PO phase, although this difference was not statistically significant (3284+/-721 vs 4542+/-872 vs 4071+/-699 microg/min/L; EF vs PO vs L; p=0.09). Similarly, deconvolution estimated GH secretion did not vary over the cycle (p=0.56). There were no differences in GH pulse amplitude or frequency. There were no correlations between IGHC and sex steroids. Serum IGF-I was constant over the cycle (272+/-38 vs 277+/-31 vs 265+/-38 microg/L; p=0.89). The TSH response to TRH and GH response to GRH did not vary over the cycle. We concluded that the effect of changes in the ovarian steroid milieu on the GH axis during spontaneous menstrual cycles is minimal.

Effects of Photoperiod on the Cessation of Growth during Autumn in Male Red Deer and Growth Hormone and Insulin-like Growth Factor-I Secretion

Male red deer undergo seasonal cycles of food intake and growth rate, which are high during spring and low during winter, despite high quality foodad libitum.Hormonal profiles during the cessation of growth in autumn and the potential role of photoperiod in the timing of the observed changes have been investigated. Whether this seasonal decrease in growth affected the response of GH and IGF-I to fasting was also examined. Two groups of six male 1-year-old red deer were exposed to different photoperiods after the summer solstice. One group (C) was given a simulated natural photoperiod while the other group (SS) was maintained on a summer solstice photoperiod (16L:8D). GH was measured in blood collected continuously and divided into pools every 5 min for 24 h in the fed state and after a 48-h fast on two occasions; the first was in November before photoperiod manipulation began and the second was in April approximately 16 weeks after initiating treatments. IGF-I, prolactin, and testosterone were measured in weekly samples. Individual live weight and group food intake were also measured each week. The normal growth pattern seen in the C group was delayed in the SS group. Thus, from 7 March until the second GH sampling on 11 April the live weight of deer in group C fell; in contrast, deer in group SS continued to grow (−43 vs 186 g/day s.e.d.=65.5,P<0.01). Food intake changes reflected the pattern of growth in both groups. Mean GH (P<0.05), GH pulse amplitude (P<0.01), and IGF-I (P<0.001) declined in both groups from November to April. This decline was more marked in group C and in April these parameters were all lower in group C than in group SS (GH,P<0.05; IGF-1,P<0.01). Prolactin levels in April were also lower in group C than in group SS (P<0.01); testosterone was not affected by treatment. Fasting increased mean GH and GH pulse amplitude in both groups in November (P<0.05). In April, the fasting response differed between the groups. In group C, mean GH, pulse amplitude, and pulse frequency were all greater in the fasted state than in the fed state (P<0.05), while in group SS there were no significant differences (P>0.05). IGF-I was lower in the fasted state than in the fed state at both sampling dates (P<0.001). The seasonal decline in food intake and growth is associated with decreased GH, IGF-I, and prolactin concentrations, and increased testosterone and the GH response associated with fasting. All these changes except those of testosterone were delayed or reduced by continued exposure to a summer solstice photoperiod in autumn. The decreased photoperiod in autumn may thus influence the normal timing of the seasonal growth cycle.

COMPARISON CF GROWTH HORMONE (GH) LEVELS MEASURED BY IMMUNORADIOKETRIC (IRMA) AND IMMUKOFLUORIMETRIC ASSAYS (IFMA) IN CHILDREN WITH SHORT. STATURE

Traditionally, the diagnosis of GH deficiency is based on maximal GH values after two stimulation tests under 7 ng/ml measured throuch IRMA. There are now more sensitive methods to measure GH such as IFMA. In this study we compared the GH response measured by IRMA and IFMA in a group of 9 children (3M; 6F) with short stature (SD for stature between -1.2 and -3.7), who were considered normal throuah two pharmacological tests for GH measured bv IRMA. We also assessed by IFMA the GH responses to stimulation tests in patients with proven GH deficiency (transecction of pituitary stalk associated with hypoplastic pituitary and ectopic neurohypophysis or multiple hypothalamic-pituitary Deficiencies) or strong clinical evidence (SD for height <-3.06) and low values of IGF-1. The IRMA and IFMA detection limit was 0.25 ng/ml ana 0.1 ng/ml respectively. In the GH deficient group, the patients had no response to stimulation tests (< 0.1 to 0.2 ng/ml at all times): in two patients the maximal values were 0.8 and 1.7 ng/ml. We observed a positive correlation (r=0.899, p < 0.0001) among the 37 GH samples measured by both methods (GH values ranging from 0.31 to 35.1 ng/ml in IRMA, and from 0.1 to 17.9 ng/ml in IFMA) in the group with normal response. We conclude that the GH values measured by IFMA are lower than by IRMA. Therefore, normal values of GH by this method must be reassessed to avoid misdiagnosis of GH deficiency.

L-THYROXINE INDUCED TSH SUPPRESSION

Thyroid hormones (TH) suppress TSH release not only as a direct effect on the pituitary, but also by inhibiting hypothalamic TRH. Endogeneous somatostatin, dopamin and calcium seem also to play a role. 25 adolescents (5 M, 20 F) receiving high doses of 1-thyroxine (3 μg/Kg/day) for endemic goiter were subdivided in 3 groups (A,B,C) and studied in two phases: in the first phase a TRH test (200 μg i.v.) was performed and TSH, PRL and GH samples taken at time 0′, 20′, 40′ and 60′. In second phase (a week later) a similar TRH test was repeated, but group A (9 pts) was given 60 mg pyridostigmine bromide (a cholinergic agonist) p.os 60′ before, group B (7 pts) received 10 mg metoclopramide (a dopamine antagonist) p.os also 60′ before, and group C (9 pts) 40 mg of verapamil (a calcium antagonist) thrice daily for one week. Basal TH were: T3 1.8±0.7 ng/ml (nv 0.8-2), T4 12.3±3.1 μ/dl (nv 4.5-12). fT3 4.8±2.3 pg/ml (nv 2.5-6), fT4 2.5±1.0 ng/dl (nv 0.8-1.9). Results (basal and peak of 1st TRH Versus 2nd TRH): in group A TSH was 0.3±0.3/0.5±0.5 μU/ml vs 0.2±0.2/0.6±0.4 μU/ml (NS). PRL was 8.9±8/22.4±11.6 ng/ml vs 6.8±6.1/23.3±12.4 ng/ml (NS), while a significant rise of GH 0.5±0.6/2.5±3.3 ng/ml vs 3.3±4.7/11.7±9.2 ng/ml (p< 0.025 for the difference between the peaks) was obtained during the 2nd phase and thus confirming the inhibition of somatostatinergic tone. In group B TSH was <0.1/0.2±0.3 vs <0.1/0.2±0.2 μU/ml (NS), a significantly higher rise of PRL was observed during the 2nd phase 10.4±3.3/21.6±12.6 ng/ml vs 9.4±3.9/58.4±17.1 ng/ml (p<0.001 for the difference between the peaks) due to a lowered dopaminergic tone, while no response of GH was seen 2.9±4.5/4.6±6.4 ng/ml vs 2.5±3.3/2.4±2.2 ng/ml (NS). In group C TSH was 0.1/0.2±0.3 vs 0.1/0.3±0.5 μU/ml, PRL 9.6±6/39.4±22.6 ng/ml vs 11.1±4.6/50±33.3 ng/ml and GH 3.5±1.9/4.1±2.4 ng/ml vs 4.4±3.1/4.1±2.3 ng/ml (NS for all).Conclusion: our results would confirm the hypothesis that the direct effect of the thyroid hormones on the TSH secretion seems to be more important than that mediated by somatostatin, dopamin and/or calcium.