scholarly journals Testosterone modulates growth hormone secretion at the hypothalamic but not at the hypophyseal level in the adult male rhesus monkey

2000 ◽  
Vol 165 (2) ◽  
pp. 337-344 ◽  
Author(s):  
SS Rizvi ◽  
GF Weinbauer ◽  
M Arslan ◽  
CJ Partsch ◽  
E Nieschlag
Keyword(s):  
Growth Hormone ◽  
Body Weight ◽  
Rhesus Monkeys ◽  
Hormone Secretion ◽  
Plasma Concentrations ◽  
Growth Hormone Secretion ◽  
Qualitative Change ◽  
Gh Secretion ◽  
Significant Difference ◽  
Male Rhesus

We investigated a possible modulation of growth hormone (GH) secretion by testosterone by measuring the growth hormone releasing hormone (GHRH)-stimulated and N-methyl-d,l-aspartic acid (NMA)-induced GH secretion in adult rhesus monkeys. Intact, orchidectomized and testosterone-substituted (testosterone enanthate 125 mg/week, i.m. for 5 weeks) orchidectomized monkeys (n=5) were used in the study. GHRH (25 microg/kg body weight) or NMA (15 mg/kg body weight) was infused through a Teflon cannula implanted in the saphenous vein. Sequential blood samples were collected 30-60 min before and 60 min after the injection of the neurohormone or the drug at 10-20-min intervals. All bleedings were carried out under ketamine hydrochloride anaesthesia (initial dose 5 mg/kg body weight i.m., followed by 2.5 mg/kg at 30-min intervals). The plasma concentrations of GH, testosterone and oestradiol (E(2)) were determined by using specific assay systems. Administration of GHRH elicited a significant increase in GH secretion in all three groups of animals. There was no significant difference in the responsiveness of pituitary somatotrophs to exogenous GHRH challenges between intact and orchidectomized monkeys and testosterone replacement in orchidectomized animals did not significantly alter the GHRH-induced GH response. The responsiveness of hypothalamic GHRH neurones apparently did undergo a qualitative change after orchidectomy, as GH response to NMA was less in orchidectomized animals than in intact monkeys. The responsiveness of GHRH neurones to exogenous NMA was restored and even potentiated when orchidectomized monkeys were treated with testosterone. Taken together, these findings suggest that testosterone does not affect the sensitivity of the pituitary somatotrophs to GHRH but stimulates the secretion of GH by modulation of the NMDA drive to GHRH neurones.

Restoration of juvenile baseline growth hormone secretion with preservation of the ultradian growth hormone rhythm by continuous delivery of growth hormone-releasing factor

1992 ◽  
Vol 135 (2) ◽  
pp. 371-382 ◽  
Author(s):  
R. Vasilatos-Younken ◽  
P. H. Tsao ◽  
D. N. Foster ◽  
D. L. Smiley ◽  
H. Bryant ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Body Weight ◽  
Bone Growth ◽  
Hormone Secretion ◽  
Plasma Concentrations ◽  
Growth Hormone Secretion ◽  
High Dose ◽  
Mrna Levels ◽  
Epiphyseal Growth Plate ◽  
Gh Secretion

ABSTRACT The ability of continuously delivered GH-releasing factor (GRF) to enhance GH secretion while maintaining the normal ultradian GH rhythm was investigated. Synthetic human GH-releasing factor (hGRF(1–44)NH2) was continuously infused for 4 days by means of i.v. catheters to 11-week-old broiler chickens. At this age, overall endogenous GH secretion is low, and baseline GH is barely detectable. Six birds per treatment received vehicle (control), 0·324 mg hGRF(1–44)NH2/kg body weight per day (low dose) or 3·24 mg hGRF(1–44)NH2/kg body weight per day (high dose). After 4 days of GRF conditioning, concurrent with continued GRF infusion, serial blood samples were removed via atrial catheters at 15-min intervals for 6 h and GH plasma profiles determined. High dose GRF significantly increased GH plasma concentrations over tenfold compared with controls; however, most of this increase reflected an increase in basal GH, which was reinstated to juvenile baseline levels. Augmentation of pulse amplitude above this increased baseline was not proportionately as high, and failed to reach juvenile levels. The ultradian rhythm of GH was not altered by continuous GRF administration. Both low and high dose GRF treatments resulted in significant enlargement of the anterior pituitary gland. Total pituitary GH mRNA levels, although elevated over twofold by GRF treatment, were not significantly different from controls. Measures of plasma GH magnitude (overall and baseline mean, and peak amplitude) were significantly correlated with pituitary GH mRNA for control birds, but were not correlated for GRF treatments. Feed intake was markedly depressed (33%) on the high dose GRF treatment, in conjunction with total inhibition of body weight gain over the 4-day period of administration. Longitudinal bone growth and width of the epiphyseal growth plate were also significantly reduced by high dose GRF treatment, probably reflecting the reduced level of nutrient intake, despite high circulating concentrations of GH. Journal of Endocrinology (1992) 135, 371–382

Effect of actively immunizing sheep against growth hormone-releasing hormone or somatostatin on spontaneous pulsatile and neostigmine-induced growth hormone secretion

1995 ◽  
Vol 144 (1) ◽  
pp. 83-90 ◽  
Author(s):  
E Magnan ◽  
L Mazzocchi ◽  
M Cataldi ◽  
V Guillaume ◽  
A Dutour ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Body Weight ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Physiological Role ◽  
Gh Secretion ◽  
Igf I ◽  
Plasma Gh ◽  
Hypophysial Portal

Abstract The physiological role of endogenous circulating GHreleasing hormone (GHRH) and somatostatin (SRIH) on spontaneous pulsatile and neostigmine-induced secretion of GH was investigated in adult rams actively immunized against each neuropeptide. All animals developed antibodies at concentrations sufficient for immunoneutralization of GHRH and SRIH levels in hypophysial portal blood. In the anti GHRH group, plasma GH levels were very low; the amplitude of GH pulses was strikingly reduced, although their number was unchanged. No stimulation of GH release was observed after neostigmine administration. The reduction of GH secretion was associated with a decreased body weight and a significant reduction in plasma IGF-I concentration. In the antiSRIH group, no changes in basal and pulsatile GH secretion or the GH response to neostigmine were observed as compared to controls. Body weight was not significantly altered and plasma IGF-I levels were reduced in these animals. These results suggest that in sheep, circulating SRIH (in the systemic and hypophysial portal vasculature) does not play a significant role in pulsatile and neostigmine-induced secretion of GH. The mechanisms of its influence on body weight and production of IGF-I remain to be determined. Journal of Endocrinology (1995) 144, 83–90

Central action of thyrotrophin-releasing hormone on growth hormone secretion in domestic fowl

1990 ◽  
Vol 126 (1) ◽  
pp. 83-88 ◽  
Author(s):  
S. Harvey ◽  
R. W. Lea ◽  
C. Ahene
Keyword(s):  
Growth Hormone ◽  
Domestic Fowl ◽  
Hormone Secretion ◽  
Plasma Concentrations ◽  
Growth Hormone Secretion ◽  
Central Effect ◽  
Central Action ◽  
Thyrotrophin Releasing Hormone ◽  
Gh Secretion ◽  
Peripheral Plasma

ABSTRACT Peripheral plasma concentrations of GH in adult chickens were increased, in a dose-related manner, between 5 and 30 min after the intracerebroventricular (i.c.v.) injection of 0·1 or 10 μg TRH. In contrast, i.v. administration of comparable doses of TRH had no significant effect on circulating GH concentrations. [3H]3-methyl-histidine2-TRH ([3H]Me-TRH) was located in the pituitary gland and peripheral plasma within 5 min of its i.c.v. administration, although in amounts that were unlikely to affect directly pituitary function. [3H]Me-TRH rapidly accumulated in the hypothalamus following its i.c.v. administration (but not after i.v. injection), and the central effect of TRH on GH secretion in birds is therefore likely to be induced by effects at hypothalamic sites. Journal of Endocrinology (1990) 126, 83–88

scholarly journals Evaluation of Prepubertal Patients with Suspected Neurosecretory Dysfunction of Growth Hormone Secretion: Diagnostic Steps and Treatment Response

2017 ◽  
Vol 2017 ◽  
pp. 1-11
Author(s):  
Carmen Sydlik ◽  
Claudia Weißenbacher ◽  
Julia Roeb ◽  
Susanne Bechtold-Dalla Pozza ◽  
Heinrich Schmidt
Keyword(s):  
Growth Hormone ◽  
Hormone Secretion ◽  
Laboratory Data ◽  
Growth Hormone Secretion ◽  
Diagnostic Procedures ◽  
Gh Treatment ◽  
Gh Secretion ◽  
Significant Difference ◽  
Stimulation Tests

Background and Aims. Existence and diagnostic procedures of neurosecretory dysfunction of growth hormone (NSD) are still a matter of debate. The aim of our study was (a) to find out if prediagnostic auxological and laboratory data could serve as an indicator for pathologic and normal spontaneous GH-secretion and (b) to evaluate the response to GH-therapy in NSD-patients. Methods. Of 90 children (unicentric study) with normal response to GH-stimulation tests, in whom 12-hour night profiles for GH-secretion were performed, 49 were diagnosed with NSD (NSD group). Their auxologic data, IGF-I/IGFBP3-levels as well as the night profiles, were analysed and compared to those of the non-NSD group. Additionally, follow-up auxological data of the GH-treated NSD-patients were collected. Results. Prediagnostic auxologic and laboratory data did not differ between the two groups. Instead, for all analysed criteria of spontaneous GH-secretion (number of peaks, maximal and mean secretion) a significant difference was found. Children with NSD showed a good response to GH-treatment after 1 (ΔH-SDS +0,77 ± 0,48) as well as 4 years (+1,51 ± 0,75). Conclusion. According to our results, analysing spontaneous GH-secretion remains the only method to identify NSD. Yet, as response to GH-treatment is comparable to results in idiopathic GHD, it is worth to consider this diagnosis.

Pituitary volume in children with growth hormone deficiency, idiopathic short stature and controls

2016 ◽  
Vol 29 (10) ◽  
Author(s):  
Marion Kessler ◽  
Michael Tenner ◽  
Michael Frey ◽  
Richard Noto
Keyword(s):  
Growth Hormone ◽  
Magnetic Resonance ◽  
Growth Hormone Deficiency ◽  
Short Stature ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Magnetic Resonance Images ◽  
Idiopathic Short Stature ◽  
Hormone Deficiency ◽  
Significant Difference

AbstractBackground:The objective of the study was to describe the pituitary volume (PV) in pediatric patients with isolated growth hormone deficiency (IGHD), idiopathic short stature (ISS) and normal controls.Methods:Sixty-nine patients (57 male, 12 female), with a mean age of 11.9 (±2.0), were determined to have IGHD. ISS was identified in 29 patients (20 male, 9 female), with a mean age of 12.7 (±3.7). Sixty-six controls (28 female, 38 male), mean age 9.8 (±4.7) were also included. Three-dimensional (3D) magnetic resonance images with contrast were obtained to accurately measure PV.Results:There was a significant difference in the mean PV among the three groups. The IGHD patients had a mean PV 230.8 (±89.6), for ISS patients it was 286.8 (±108.2) and for controls it was 343.7 (±145.9) (p<0.001). There was a normal increase in PV with age in the ISS patients and controls, but a minimal increase in the IGHD patients.Conclusions:Those patients with isolated GHD have the greatest reduction in PV compared to controls and the patients with ISS fall in between. We speculate that a possible cause for the slowed growth in some ISS patients might be related to diminished chronic secretion of growth hormone over time, albeit having adequate pituitary reserves to respond acutely to GH stimulation. Thus, what was called neurosecretory GHD in the past, might, in some patients, be relative pituitary hypoplasia and resultant diminished growth hormone secretion. Thus, PV determinations by magnetic resonance imaging (MRI) could assist in the diagnostic evaluation of the slowly growing child.

Studies on the involvement of calcium and calmodulin in the action of growth-hormone-releasing factor

1984 ◽  
Vol 4 (12) ◽  
pp. 995-1000 ◽  
Author(s):  
Janet E. Merritt ◽  
Pauline R. M. Dobson ◽  
Richard J. H. Wojcikiewicz ◽  
John G. Baird ◽  
Barry L. Brown
Keyword(s):  
Growth Hormone ◽  
Cyclic Amp ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Calcium Mobilization ◽  
Basal Secretion ◽  
Calmodulin Antagonist ◽  
Growth Hormone Releasing Factor ◽  
Gh Secretion

A possible role for Ca 2+ and calmodulin in the action of growth-hormone-releasing factor (GHRF) was investigated. Low extracellular Ca2+ (<100 μM), methoxyverapamil, flunarizine, cinnarizine, and Co2+ decreased both basal and GHRF-stimulated growth-hormone secretion, but did not totally inhibit GHRF-stimulation secretion. A calmodulin antagonist, W7, abolished GHRF-stimulated GH secretion, with no effect on basal secretion. It is suggested that GHRF may act primarily by elevating cellular cyclic AMP, which may then modulate calcium mobilization or flux; the increased intracellular Ca2+ concentrations may then activate calmodulin.

A possible relationship between serum transferrin, growth hormone secretion and height velocity in children

1980 ◽  
Vol 93 (2) ◽  
pp. 134-138 ◽  
Author(s):  
M. Donnadieu ◽  
R. M. Schimpff ◽  
P. Garnier ◽  
J. L. Chaussain ◽  
J. C. Job
Keyword(s):  
Growth Hormone ◽  
Growth Regulation ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Height Velocity ◽  
Obese Children ◽  
Gh Secretion ◽  
Growth Promoting

Abstract. Since transferrin (Tf) in vitro has a growth-promoting activity and is associated with NSILA properties, the aim of this work was to study in vivo the relationships between Tf, somatomedin activity (SM), growth hormone (GH) secretion, and height velocity in children. An iv infusion of ornithine hydrochloride was given to 23 controls; the induced rise of GH was accompanied by a simultaneous fall of SM (r = −0.711, P < 0.001) and was preceded by a fall of Tf (r = −0.610, P < 0.01). In 17 obese children SM was within the normal range, when Tf levels were higher and arginineinduced GH peaks lower than in the controls, and a negative correlation was found between Tf basal levels and GH peaks (r = −0.608, P < 0.01). In 9 children with confirmed hypopituitarism the Tf levels were significantly lower than in the controls. In 14 children with confirmed or suspected hypopituitarism a single im injection of hGH (6 mg) failed to induce Tf variations over 24 h. In 39 of these children the height velocity was significantly correlated with Tf basal levels (r = 0.701, P < 0.001). These data suggest that transferrin is involved in growth regulation, and that GH secretion is related to transferrin levels by a feed-back mechanism.

Glucocorticoid modulation of growth hormone secretion in vitro. Evidence for a biphasic effect on GH-releasing hormone mediated release

1987 ◽  
Vol 114 (4) ◽  
pp. 465-469 ◽  
Author(s):  
Gian Paolo Ceda ◽  
Robert G. Davis ◽  
Andrew R. Hoffman
Keyword(s):  
Growth Hormone ◽  
Prolonged Exposure ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Inhibitory Effect ◽  
Pituitary Cells ◽  
Gh Secretion ◽  
Glucocorticoid Action

Abstract. Glucocorticoids have been shown to have both stimulatory and suppressive effects on GH secretion in vitro and in vivo. In order to study the kinetics of glucocorticoid action on the somatotrope, cultured rat pituitary cells were exposed to dexamethasone for varying periods of time. During short-term incubations (≤ 4 h), dexamethasone inhibited GHRH and forskolin-elicited GH secretion, but during longer incubation periods, the glucocorticoid enhanced both basal and GHRH-stimulated GH release. The inhibitory effect of brief dexamethasone exposure was also seen in cells which previously had been exposed to dexamethasone. In addition, growth hormone secretion from cultured rat and human somatotropinoma cells was inhibited by a brief exposure to dexamethasone. Thus, the nature of glucocorticoid action on the isolated cultured somatotrope is biphasic, with brief exposure inhibiting, and more prolonged exposure stimulating GH secretion.

scholarly journals Growth Hormone Secretion After Conformal Radiation Therapy in Pediatric Patients With Localized Brain Tumors

2011 ◽  
Vol 29 (36) ◽  
pp. 4776-4780 ◽  
Author(s):  
Thomas E. Merchant ◽  
Susan R. Rose ◽  
Christina Bosley ◽  
Shengjie Wu ◽  
Xiaoping Xiong ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Radiation Therapy ◽  
Radiation Dose ◽  
Brain Tumors ◽  
Pediatric Patients ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Low Grade ◽  
Conformal Radiation Therapy ◽  
Gh Secretion

Purpose Growth hormone deficiency (GHD) after radiation therapy negatively affects growth and development and quality of life in children with brain tumors. Patients and Materials Between 1997 and 2008, 192 pediatric patients with localized primary brain tumors (ependymoma, n = 88; low-grade glioma, n = 51; craniopharyngioma, n = 28; high-grade glioma, n = 23; and other tumor types, n = 2) underwent provocative testing of GH secretion by using the secretogogues arginine and l-dopa before and after (6, 12, 36, and 60 months) conformal radiation therapy (CRT). A total of 664 arginine/l-dopa test procedures were performed. Results Baseline testing revealed preirradiation GHD in 22.9% of tested patients. On the basis of data from 118 patients, peak GH was modeled as an exponential function of time after CRT and mean radiation dose to the hypothalamus. The average patient was predicted to develop GHD with the following combinations of the time after CRT and mean dose to the hypothalamus: 12 months and more than 60 Gy; 36 months and 25 to 30 Gy; and 60 months and 15 to 20 Gy. A cumulative dose of 16.1 Gy to the hypothalamus would be considered the mean radiation dose required to achieve a 50% risk of GHD at 5 years (TD50/5). Conclusion GH secretion after CRT can be predicted on the basis of dose and time after irradiation in pediatric patients with localized brain tumors. These findings provide an objective radiation dose constraint for the hypothalamus.

scholarly journals Molecular evolution of the growth hormone-releasing hormone/pituitary adenylate cyclase-activating polypeptide gene family. Functional implication in the regulation of growth hormone secretion

2000 ◽  
Vol 25 (2) ◽  
pp. 157-168 ◽  
Author(s):  
M Montero ◽  
L Yon ◽  
S Kikuyama ◽  
S Dufour ◽  
H Vaudry
Keyword(s):  
Growth Hormone ◽  
Molecular Evolution ◽  
Adenylate Cyclase ◽  
Gene Family ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Growth Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Gh Secretion ◽  
Pituitary Adenylate Cyclase

Growth hormone-releasing hormone (GHRH) and pituitary adenylate cyclase-activating polypeptide (PACAP) belong to the same superfamily of regulatory neuropeptides and have both been characterized on the basis of their hypophysiotropic activities. This review describes the molecular evolution of the GHRH/PACAP gene family from urochordates to mammals and presents the hypothesis that the respective roles of GHRH and PACAP in the control of GH secretion are totally inverted in phylogenetically distant groups of vertebrates. In mammals, GHRH and PACAP originate from distinct precursors whereas, in all submammalian taxa investigated so far, including birds, amphibians and fish, a single precursor encompasses a GHRH-like peptide and PACAP. In mammals, GHRH-containing neurons are confined to the infundibular and dorsomedial nuclei of the hypothalamus while PACAP-producing neurons are widely distributed in hypothalamic and extrahypothalamic areas. In fish, both GHRH- and PACAP-immunoreactive neurons are restricted to the diencephalon and directly innervate the adenohypophysis. In mammals and birds, GHRH plays a predominant role in the control of GH secretion. In amphibians, both GHRH and PACAP are potent stimulators of GH release. In fish, PACAP strongly activates GH release whereas GHRH has little or no effect on GH secretion. The GHRH/PACAP family of peptides thus provides a unique model in which to investigate the structural and functional facets of evolution.

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