Growth hormone responses to growth hormone-releasing factor (1–29) in euthyroid, hypothyroid and hyperthyroid rats

1986 ◽  
Vol 109 (1) ◽  
pp. 53-56 ◽  
Author(s):  
C. Dieguez ◽  
V. Jordan ◽  
P. Harris ◽  
S. Foord ◽  
M. D. Rodriguez-Arnao ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Growth Hormone Releasing Factor ◽  
Time Points ◽  
Gh Secretion ◽  
Hormone Responses ◽  
Plasma Gh

ABSTRACT In order to investigate whether the impaired GH secretion associated with hypothyroidism and hyperthyroidism is due to a hypothalamic or a pituitary disorder, we have studied plasma GH responses to GH-releasing factor (1–29) (GRF) in euthyroid, hypothyroid and hyperthyroid rats. Hypothyroid rats showed a significant (P< 0·001) reduction in GH responses to GRF (5 μg/kg) at 5 min (350 ± 35 vs 1950 ±260 μg/l), 10 min (366±66 vs 2320 ± 270 μg/l) and 15 min after GRF injection (395 ± 72 vs 1420 ± 183 μg/l; means ± s.e.m.) compared with euthyroid rats. Hyperthyroid rats showed a significant (P<0·05) decrease in GH responses to 5 μg GRF/kg after 30 min (200±14 vs 325 ± 35 μg/l) but not at other time-points, or after the administration of 1 μg GRF/kg. These data indicate that in hypothyroidism and perhaps hyperthyroidism there is an alteration in the responsiveness of the somatotroph to GRF administration. J. Endocr (1986) 109, 53–56

Growth hormone responses to low-dose physostigmine administration: functional sex differences (sexual diergism) between major depressives and matched controls

2003 ◽  
Vol 33 (4) ◽  
pp. 655-665 ◽  
Author(s):  
R. T. RUBIN ◽  
S. A. ABBASI ◽  
M. E. RHODES ◽  
R. K. CZAMBEL
Keyword(s):  
Growth Hormone ◽  
Sex Differences ◽  
Side Effects ◽  
Low Dose ◽  
Hormone Secretion ◽  
Saline Control ◽  
Similar Degree ◽  
Gh Secretion ◽  
Hormone Responses ◽  
Plasma Gh

Background. Considerable endocrine and non-endocrine evidence supports the hypothesis of increased cholinergic activity relative to noradrenergic activity in major depression. We previously reported functional sex differences (sexual diergism) in hypothalamo–pituitary–adrenal cortical (HPA) hormone responses to the administration of low-dose physostigmine (PHYSO), a cholinesterase inhibitor, in 12 female and eight male unipolar major depressives and 12 female and eight male individually matched control subjects. Because growth hormone (GH) secretion also is influenced by cholinergic mechanisms, we measured GH in the samples from this study.Method. Subjects underwent four test sessions 5–7 days apart: PHYSO (8 μg/kg i.v.), arginine vasopressin (AVP) (0·08 U/kg i.m.), PHYSO+AVP and saline control. The AVP was administered as a second stimulus to HPA axis hormone secretion. PHYSO and AVP produced no side-effects in about half the subjects and predominantly mild side-effects in the other half, with no significant patient–control differences. Point biserial correlations between side-effects (absent or present) after PHYSO and the corresponding GH responses were non-significant in all groups.Results. Afternoon baseline GH was significantly higher in the women than in the men, but it was not significantly different between the female or the male patients and their respective matched controls. AVP administration had no effect on GH. PHYSO administration acutely stimulated GH secretion, to a similar degree in the women and men. The depressed patients as a group had a significantly greater average post-PHYSO GH response than did their controls, with a trend toward a significant sex×diagnosis interaction: The female depressives had a significantly greater GH response than their female controls, whereas the male depressives had a similar GH response as their male controls.Conclusions. These findings suggest sexual diergism (functional sex differences) in baseline and cholinergically stimulated plasma GH measures between major depressives and matched normal controls.

Evidence against growth hormone-releasing factor deficiency in children with idiopathic obesity

1986 ◽  
Vol 113 (4_Suppl) ◽  
pp. S403-S410 ◽  
Author(s):  
G. VAN VLIET ◽  
D. BOSSON ◽  
E. RUMMENS ◽  
C. ROBYN ◽  
R. WOLTER
Keyword(s):  
Growth Hormone ◽  
Peak Plasma ◽  
Obese Children ◽  
Somatomedin C ◽  
Growth Hormone Releasing Factor ◽  
Gh Secretion ◽  
Lean Control ◽  
Factor Deficiency ◽  
Plasma Gh ◽  
Lean Children

Abstract The mechnisms whereby growth hormone (GH) secretion is decreased in human obsity remain obscure. We studied the response of plasma GH and prolactin (PRL) to an I.V. dose of 0.5 mcg/kg of growth hormone releasing factor (GRF) in three groups of children: lean (N=12), obese (N=15) and GRF-deficient, i.e. children with complete GH deficiency on the basis of conventional provocative testing and evidence of hypothalamic dyfunction on the basis of thyrotropin-releasing hormone testing (N=7). Mean (±SEM) peak plasma GH after GRF was blunted to the same extent in obese and in GRF deficient children (11.1 ± 2.2 and 8.3 ± 2.8 mg/ml) as compared to lean control children (34.7 ± 4.7 mg/ml). The pattern of PRL response to GRF was however different in GRF after GRF injection, and in obese and lean children, who had no acute change in PRL levels after GRF. Baseline plasma somatomedin C concentrations were low for age in GRF deficient children and tended to be high for age in obese children. On the basisi of these discrepant patterns of response of PRL to GRF and plasma somatomedin C concentration, we conculde that GRF defeciency does not account for the decreased GH secreation observed in obese children.

Pyridostigmine-induced growth hormone responses in healthy and depressed subjects: evidence for cholinergic supersensitivity in depression

1992 ◽  
Vol 22 (1) ◽  
pp. 55-60 ◽  
Author(s):  
V. O'Keane ◽  
K. O'Flynn ◽  
J. Lucey ◽  
T. G. Dinan
Keyword(s):  
Growth Hormone ◽  
Broad Spectrum ◽  
Clinical Observation ◽  
Healthy Controls ◽  
Time Points ◽  
Cholinergic Agent ◽  
Hormone Responses ◽  
Plasma Gh ◽  
Age And Sex ◽  
Probe Approach

SYNOPSISTheorists have extrapolated the cholinergic supersensitivity theory of affective disorder from a convincing and broad spectrum of clinical observation and research. This hypothesis is tested using a neuroendocrine probe approach with the challenge drug pyridostigmine, an indirect cholinergic agent thought to release growth hormone (GH) by decreasing inhibitory somatostatin tone. The consequent increments in plasma GH were considered to reflect central acetylcholine responsivity. Fifty-four volunteers were tested: 27 DSM-III-R major depressives (18 women and 9 men) and 27 age- and sex-matched healthy controls. Subjects were cannulated at 9.00 h following an overnight fast and two baseline samples were taken at 15 min intervals. Pyridostigmine 120 mg was administered orally and thereafter samples were taken at the time points +60, +90, +120 and +180 min. GH responses were significantly greater in depressives than controls and this effect was more marked for men than women. These results support the proposal that muscarinic upregulation and/or supersensitivity is associated with depression.

GROWTH HORMONE RESPONSES TO FRUCTOSE IN DIABETES MELLITUS

1974 ◽  
Vol 75 (3) ◽  
pp. 497-502
Author(s):  
Mayer B. Davidson ◽  
Roger M. Steele
Keyword(s):  
Diabetes Mellitus ◽  
Growth Hormone ◽  
Fasting Glucose ◽  
Area Under The Curve ◽  
Oral Glucose ◽  
Gh Secretion ◽  
Significant Difference ◽  
Duration Of Disease ◽  
Hormone Responses

ABSTRACT Since fructose is normally metabolized in diabetics and has recently been shown to stimulate GH secretion, it was used to assess GH responses in diabetics. Fourteen diabetics (9 on insulin) and 8 controls matched for weight were studied. Fructose, infused over 10 min, was compared to arginine, infused over 30 min, both at 0.5 g/kg. Samples were collected at 0, 30, 60, 90 and 120 min and GH responses assessed as area under the curve minus the fasting area. There was no significant difference between the GH responses in diabetics and controls to either agent. Responses to arginine and fructose were significantly correlated (r = 0.60, P < 0.01) in all subjects, but not related to therapy, duration of disease or fasting glucose (75–287 mg/100 ml) in the diabetics. Oral glucose blunted the GH response to fructose in 2 controls. It is concluded that 1) fructose can stimulate GH secretion in male diabetics; 2) however, fructose-stimulated GH responses are not increased in diabetes mellitus.

Is there a place for urinary growth hormone measurement?

1993 ◽  
Vol 128 (3) ◽  
pp. 197-201 ◽  
Author(s):  
Maria N Moreira-Andrés ◽  
Francisco J Cañizo ◽  
Federico Hawkins
Keyword(s):  
Growth Hormone ◽  
Screening Method ◽  
Small Sample ◽  
Point Of View ◽  
Intrasubject Variability ◽  
Gh Secretion ◽  
Lack Of Information ◽  
Low Levels ◽  
Plasma Gh ◽  
Serum Gh

The evaluation of growth hormone (GH) secretion is an important problem in pediatric endocrine practice. The diagnosis of GH insufficiency is based on the finding of a "blunted" GH response to GH provocative tests or on the demonstration of a decreased endogenous secretion. From a practical point of view, these methods are uncomfortable, expensive and time consuming. Recently, very sensitive specific assays to measure human GH in urine have been developed. We present a discussion of available data on these tests in order to estimate their role in the evaluation of a short or slowly growing child. The present available assays allow measuring very low levels of GH in a small sample of untreated urine. The main limitations of urinary GH measurement are the intrasubject variability, wide normal range, overlapping results in several GH secretory states and lack of information on GH pulsatility. However, most of these limitations also apply to other tests of GH secretion. The advantage of urinary GH tests is that they provide, in an easy procedure, information on serum GH concentration. There is good correlation between urinary and serum GH concentration and several findings suggest that urinary GH excretion reflects changes in plasma GH levels during the period of urine collection. Therefore, the usefulness of urinary GH measurement is that of a simpler and cheaper screening method for assessing integrated serum GH concentration in clinical practice.

Growth hormone-releasing factor enhances sleep in rats and rabbits

1988 ◽  
Vol 255 (2) ◽  
pp. R310-R316 ◽  
Author(s):  
F. Obal ◽  
P. Alfoldi ◽  
A. B. Cady ◽  
L. Johannsen ◽  
G. Sary ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Motor Activity ◽  
Eye Movement ◽  
Brain Temperature ◽  
Sleep Onset ◽  
Temporal Correlation ◽  
Diurnal Rhythms ◽  
Sleep Regulation ◽  
Growth Hormone Releasing Factor ◽  
Gh Secretion

Previously, it was suggested that a hypothalamic mechanism links somatotropin [growth hormone (GH)] secretion to sleep regulation, and this may explain the temporal correlation between GH release and nonrapid eye movement sleep (NREMS) on sleep onset. The purpose of these experiments was to study whether growth hormone-releasing factor (GRF), a hypothalamic peptide responsible for stimulation of GH secretion, also has the capacity to promote sleep in rats and rabbits. Artificial cerebrospinal fluid or GRF (human GRF-[1-40], 0.01, 0.1, and 1 nmol/kg) was intracerebroventricularly injected to rats at dark onset, and the electroencephalogram (EEG), brain temperature (Tbr), and motor activity were recorded for 24 h. Rabbits received the same doses of GRF during the light period, and sleep-wake activity was monitored for 6 h. GRF promoted NREMS and rapid eye movement sleep (REMS) and increased EEG slow-wave activity in both rats and rabbits. NREMS increased in postinjection hour 1 after low doses of GRF, whereas the effect was more prolonged after higher doses. REMS increased in response to the low and middle doses of GRF in postinjection hour 1 in rats and in hour 2 after each dose in rabbits. The diurnal rhythms of sleep-wake activity, motor activity, and Tbr were not affected in rats. Because GRF promotes sleep and also stimulates GH secretion, it is a likely candidate for linking GH secretion and sleep regulation.

Mechanism of action of Hexarelin. I. Growth hormone-releasing activity in the rat

1996 ◽  
Vol 135 (4) ◽  
pp. 481-488 ◽  
Author(s):  
Antonio Torsello ◽  
Roberta Grilli ◽  
Marina Luoni ◽  
Margherita Guidi ◽  
Maria Cristina Ghigo ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Mechanism Of Action ◽  
Direct Action ◽  
Male Rats ◽  
Surgical Ablation ◽  
Adult Rats ◽  
Gh Secretion ◽  
Plasma Gh

Torsello A, Grilli R, Luoni M, Guidi M, Ghigo MC, Wehrenberg WB, Deghenghi R, Müller EE, Locatelli V. Mechanism of action of Hexarelin. I. Growth hormone-releasing activity in the rat. Eur J Endocrinol 1996;135:481–8. ISSN 0804–4643 We have reported Hexarelin (HEXA), an analog of growth hormone-releasing peptide 6 (GHRP-6), potently stimulates growth hormone (GH) secretion in infant and adult rats. This study was undertaken to further investigate Hexarelin's mechanisms of action. In 10-day-old pups, treatments with HEXA (80 μg/kg, b.i.d.) for 3–10 days significantly enhanced, in a time-related fashion, the GH response to an acute HEXA challenge. Qualitatively similar effects were elicited in pups passively immunized against growth hormone-releasing hormone (GHRH) from birth. In adult male rats, a 5-day pretreatment with HEXA (150 μg/kg, b.i.d.) did not enhance the effect of the acute challenge, and the same pattern was present after a 5-day pretreatment in male rats with surgical ablation of the mediobasal hypothalamus (MBH-ablated rats). In addition, in adult sham-operated rats, Hexarelin (300 μg/kg, iv) induced a GH response greater (p < 0.05) than that induced by GHRH (2 μg/kg, iv). However, in MBH-ablated rats 7 days after surgery, GHRH was significantly (p < 0.05) more effective than HEXA, and 30 days after surgery HEXA and GHRH evoked similar rises of plasma GH. Finally, the in vitro Hexarelin (10−6 mol/l) effect was transient while GHRH (10−8 mol/l) induced a longer lasting and greater GH release. Three different mechanisms, not mutually exclusive, are postulated for Hexarelin stimulation of GH secretion in vivo: a direct action on the pituitary, though of minor relevance; an indirect action that involves release of GHRH, of relevance only in adult rats; and an action through the release of a still unknown hypothalamic "factor", which in infant and adult rats elicits GH release acting sinergistically with GHRH. Antonio Torsello, Department of Pharmacology, via Vanvitelli 32, 20129 Milano, Italy

Estimation of growth hormone secretion rate: impact of kinetic assumptions intrinsic to the analytical approach

2001 ◽  
Vol 280 (1) ◽  
pp. R225-R232 ◽  
Author(s):  
Janneke G. Langendonk ◽  
Johannes D. Veldhuis ◽  
Jacobus Burggraaf ◽  
Rik C. Schoemaker ◽  
Adam F. Cohen ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Analytical Approach ◽  
Normal Weight ◽  
Secretion Rate ◽  
The Other ◽  
Upper Body ◽  
Metabolic Clearance ◽  
Obese Women ◽  
Gh Secretion ◽  
Plasma Gh

We compared four common mathematical techniques to determine daily endogenous growth hormone (GH) secretion rates from diurnal plasma GH concentration profiles in 24 women (16 upper- or lower-body obese and 8 normal-weight individuals). Two forms of deconvolution analysis and two techniques based on a priori determined GH clearance estimates were employed. Deconvolution analyses revealed significant differences in the 24-h GH secretion rate between normal-weight and upper-body obese women, whereas the other two techniques did not. Moreover, deconvolution analyses predicted that the reduction in mean plasma GH concentrations in upper-body obese women was accounted for by impaired GH secretion, whereas the other methods suggested that obesity increases GH metabolic clearance. Thus we infer that disparate conclusions concerning GH secretion can be drawn from the same primary data set. The different inferences likely reflect dissimilar kinetic assumptions and the particular limitations intrinsic to each analytical approach. Accordingly, we urge caution in the facile comparison of calculated GH secretion data in humans, especially when kinetic and secretion measurements are performed under different conditions. The most appropriate way to determine the GH secretion rate in humans must be balanced by the exact intent of the experiment and the acceptability of different assumptions in that context.

Growth Hormone Responses to Growth Hormone Releasing Factor in Neonates

Neonatology ◽  
1985 ◽  
Vol 47 (6) ◽  
pp. 367-370 ◽  
Author(s):  
Satoshi Shimano ◽  
Shigeyoshi Suzuki ◽  
Kanji Nagashima ◽  
Hideki Yagi ◽  
Masao Sakaguchi ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Growth Hormone Releasing Factor ◽  
Hormone Responses
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