Effects Of Growth Hormone Administration Research Articles

Effects of growth hormone administration on luteinizing hormone secretion in healthy older men and women.

The known interactions between the somatotropic and hypothalamic‐pituitary‐gonadal (HPG) axes have not been well delineated in older individuals. Aging‐associated decline in insulin like growth factor‐1 (IGF‐1) levels has been proposed to play a role in reproductive senescence in animals. However, the effects of GH on LH secretion are unknown in older individuals. Our objective was to determine whether GH modulates LH secretion or levels of sex steroids (SS) in healthy older (ages 65–88 years) men (n = 24) and women (n = 24) with low‐normal plasma IGF‐1 levels. In a double‐masked, placebo‐controlled (n = 24), randomized study, we evaluated the effects of GH (n = 24, 20 μg/kg sc 3×/week) for 26 weeks on nocturnal LH secretory dynamics [(8 pm to 8 am, Q20) min sampling and analyzed by multiparameter deconvolution algorithm]. Indices of LH secretion [frequency, mass per burst, pulsatile production rate, and approximate entropy (ApEn)] and fasting serum IGF‐1, SHBG, and SS (TT, fT, or E2) were measured. At baseline, all indices of LH secretion (frequency, mass per burst, pulsatile production rate) were inversely (P < 0.05) related to IGF‐1, but not to mean nocturnal serum GH concentrations. GH administration for 26 weeks increased serum IGF‐1, but exerted no significant effects on LH secretory dynamics, or concentrations of SSs (TT, fT, or E2) or SHBG in older women or men. These data suggest that GH‐mediated increases in IGF‐1 do not modulate the HPG axis in older individuals.

Differential effects of short-term β agonist and growth hormone treatments on expression of myosin heavy chain IIB and associated metabolic genes in sheep muscle

Growth hormone (GH) and β agonists increase muscle mass, but the mechanisms for this response are unclear and the magnitude of response is thought to vary with age of animal. To investigate the mechanisms driving the muscle response to these agents, we examined the effects of short-term (6 day) administration of GH or cimaterol (a β2-adrenergic agonist, BA) on skeletal muscle phenotype in both young (day 60) and mature (day 120) lambs. Expression of myosin heavy chain (MyHC) isoforms were measured in Longissimus dorsi (LD), Semitendinosus (ST) and Supraspinatus (SS) muscles as markers of fibre type and metabolic enzyme activities were measured in LD. To investigate potential mechanisms regulating the changes in fibre type/metabolism, expression or activity of a number of signalling molecules were examined in LD. There were no effects of GH administration on MyHC isoform expression at either the mRNA or protein level in any of the muscles. However, BA treatment induced a proportional change in MyHC mRNA expression at both ages, with the %MyHCI and/or IIA mRNA being significantly decreased in all three muscles and %MyHCIIX/IIB mRNA significantly increased in the LD and ST. BA treatment induced de novo expression of MyHCIIB mRNA in LD, the fastest isoform not normally expressed in sheep LD, as well as increasing expression in the other two muscles. In the LD, the increased expression of the fastest MyHC isoforms (IIX and IIB) was associated with a decrease in isocitrate dehydrogenase activity, but no change in lactate dehydrogenase activity, indicating a reduced capacity for oxidative metabolism. In both young and mature lambs, changes in expression of metabolic regulatory factors were observed that might induce these changes in muscle metabolism/fibre type. In particular, BA treatment decreased PPAR-γ coactivator-1β mRNA and increased receptor-interacting protein 140 mRNA. The results suggest that the two agents work via different mechanisms or over different timescales, with only BA inducing changes in muscle mass and transitions to a faster, less oxidative fibre type after a 6-day treatment.

Effects of growth hormone administration for 6 months on bone turnover and bone marrow fat in obese premenopausal women

PurposeAbdominal adiposity is associated with low BMD and decreased growth hormone (GH) secretion, an important regulator of bone homeostasis. The purpose of our study was to determine the effects of a short course of GH on markers of bone turnover and bone marrow fat in premenopausal women with abdominal adiposity. Materials and methodsIn a 6-month, randomized, double-blind, placebo-controlled trial we studied 79 abdominally obese premenopausal women (21–45y) who underwent daily sc injections of GH vs. placebo. Main outcome measures were body composition by DXA and CT, bone marrow fat by proton MR spectroscopy, P1NP, CTX, 25(OH)D, hsCRP, undercarboxylated osteocalcin (ucOC), preadipocyte factor 1 (Pref 1), apolipoprotein B (ApoB), and IGF-1. ResultsGH increased IGF-1, P1NP, 25(OH)D, ucOC, bone marrow fat and lean mass, and decreased abdominal fat, hsCRP, and ApoB compared with placebo (p<0.05). There was a trend toward an increase in CTX and Pref-1. Among all participants, a 6-month increase in IGF-1 correlated with 6-month increase in P1NP (p=0.0005), suggesting that subjects with the greatest increases in IGF-1 experienced the greatest increases in bone formation. A six-month decrease in abdominal fat, hsCRP, and ApoB inversely predicted 6-month change in P1NP, and 6-month increase in lean mass and 25(OH)D positively predicted 6-month change in P1NP (p≤0.05), suggesting that subjects with greatest decreases in abdominal fat, inflammation and ApoB, and the greatest increases in lean mass and 25(OH)D experienced the greatest increases in bone formation. A six-month increase in bone marrow fat correlated with 6-month increase in P1NP (trend), suggesting that subjects with the greatest increases in bone formation experienced the greatest increases in bone marrow fat. Forward stepwise regression analysis indicated that increase in lean mass and decrease in abdominal fat were positive predictors of P1NP. When IGF-1 was added to the model, it became the only predictor of P1NP. ConclusionGH replacement in abdominally obese premenopausal women for 6months increased bone turnover and bone marrow fat. Reductions in abdominal fat, and inflammation, and increases in IGF-1, lean mass and vitamin D were associated with increased bone formation. The increase in bone marrow fat may reflect changes in energy demand from increased bone turnover.

Effects of Growth Hormone Administration on Muscle Strength in Men over 50 Years Old

Growth hormone (GH) use has been speculated to improve physical capacity in subjects without GH deficiency (GHD) through stimulation of collagen synthesis in the tendon and skeletal muscle, which leads to better exercise training and increased muscle strength. In this context, the use of GH in healthy elderly should be an option for increasing muscle strength. Our aim was to evaluate the effect of GH therapy on muscle strength in healthy men over 50 years old. Fourteen healthy men aged 50–70 years were evaluated at baseline for body composition and muscle strength (evaluated by leg press and bench press exercises, which focus primarily on quadriceps—lower body part and pectoralis major—upper body part—muscles, resp.). Subjects were randomised into 2 groups: GH therapy (7 subjects) and placebo (7 subjects) and reevaluated after 6 months of therapy. Thirteen subjects completed the study (6 subjects in the placebo group and 7 subjects in the GH group). Subjects of both groups were not different at baseline. After 6 months of therapy, muscle strength in the bench press responsive muscles did not increase in both groups and showed a statistically significant increase in the leg press responsive muscles in the GH group. Our study demonstrated an increase in muscle strength in the lower body part after GH therapy in healthy men. This finding must be considered and tested in frail older populations, whose physical incapacity is primarily caused by proximal muscle weakness. The trial was registered with NCT01853566.

Growth hormone therapy and craniofacial bones: a comprehensive review

Growth hormone (GH) has significant effects on linear bone growth, bone mass and bone metabolism. The primary role of GH supplementation in children with GH deficiency, those born small for gestational age or with other types of disorders in somatic development is to increase linear growth. However, GH therapy seems to elicit varying responses in the craniofacial region. Whereas the effects of GH administration on somatic development are well documented, comparatively little is known of its effects on the craniofacial region. The purpose of this review was to search the literature and compile results from both animal and human studies related to the impact of GH on craniofacial growth.

Growth hormone upregulates intestinal trefoil factor expression in the ileum of rats after γ-radiation

Growth hormone (GH) and intestinal trefoil factor (ITF) have been involved in intestinal protection and repair. This study investigates the effects of GH administration on ITF expression and histological changes associated with tissue injury in an intestinal rat model of radiation. Adult male rats were divided into four groups: control, GH, radiation and radiation + GH (GHyRAD). Ileum samples were obtained at 2 or 72 h after radiation and processed to determine ITF levels (mRNA and protein) by quantitative polymerase chain reaction, Western blot and immunohistochemistry. In addition, goblet ITF-positive cells were identified by immunohistochemistry at 72 h. Our results showed an upregulation of mRNA and protein production of ITF in ileum samples after GH and radiation + GH compared with control and irradiated samples. Irradiation alone affected ITF protein expression. However, irradiation after GH pretreatment produced the highest ITF mRNA and protein levels at both the tested time points. ITF-producing goblet cells were identified in intestinal villi (apical location). GH treatment increased the number of ITF-producing goblet cells, and radiation after GH treatment displayed further increase in the number of ITF-positive goblet cells. GH upregulates ITF in normal intestinal tissue. This upregulation is higher when radiation is given after GH treatment. Nevertheless, the mechanism by which GH regulates ITF expression remains unclear and is still under investigation. These results could open up new avenues in the therapeutic reparative and protective effects of GH during radiotherapy and chemotherapy.

Effects of Growth Hormone Administration on Bone Mineral Metabolism, PTH Sensitivity and PTH Secretory Rhythm in Postmenopausal Women With Established Osteoporosis

Growth hormone (GH) replacement improves target organ sensitivity to PTH, PTH circadian rhythm, calcium and phosphate metabolism, bone turnover, and BMD in adult GH-deficient (AGHD) patients. In postmenopausal women with established osteoporosis, GH and insulin like growth factor-1 (IGF-1) concentrations are low, and administration of GH has been shown to increase bone turnover and BMD, but the mechanisms remain unclear. We studied the effects of GH administration on PTH sensitivity, PTH circadian rhythm, and bone mineral metabolism in postmenopausal women with established osteoporosis. Fourteen postmenopausal women with osteoporosis were compared with 14 healthy premenopausal controls at baseline that then received GH for a period of 12 mo. Patients were hospitalized for 24 h before and 1, 3, 6, and 12 mo after GH administration and half-hourly blood and 3-h urine samples were collected. PTH, calcium (Ca), phosphate (PO(4)), nephrogenous cyclic AMP (NcAMP), beta C-telopeptide of type 1 collagen (betaCTX), procollagen type I amino-terminal propeptide (PINP), and 1,25-dihydroxyvitamin D [1,25(OH)(2)D] were measured. Circadian rhythm analysis was performed using Chronolab 3.0 and Student's t-test and general linear model ANOVAs for repeated measures were used where appropriate. IGF-1 concentration was significantly lower in the women with established osteoporosis compared with controls (101.5 +/- 8.9 versus 140.9 +/- 10.8 mug/liter; p < 0.05) and increased significantly after 1, 3, 6, and 12 mo of GH administration (p < 0.001). Twenty-four-hour mean PTH concentration was higher in the osteoporotic women (5.4 +/- 0.1 pM) than in healthy controls (4.4 +/- 0.1 pM, p < 0.001) and decreased after 1 (5.2 +/- 0.1 pM, p < 0.001), 3 (5.0 +/- 0.1 pM, p < 0.001), 6 (4.7 +/- 0.1 pM, p < 0.001), and 12 mo (4.9 +/- 0.1 pM, p < 0.05) of GH administration compared with baseline. NcAMP was significantly lower in osteoporotic women (17.2 +/- 1.2 nM glomerular filtration rate [GFR]) compared with controls (21.4 +/- 1.4 nM GFR, p < 0.05) and increased after 1 (24.2 +/- 2.5 nM GFR, p < 0.05), 3 (27.3 +/- 1.5 nM GFR, p < 0.001), and 6 mo (32.4 +/- 2.5 nM GFR, p < 0.001) compared with baseline. PTH secretion was characterized by two peaks in premenopausal women and was altered in postmenopausal women with a sustained increase in PTH concentration. GH administration also restored a normal PTH secretory pattern in the osteoporotic women. The 24-h mean adjusted serum calcium (ACa) concentration increased at 1 and 3 mo (p < 0.001) and PO(4) at 1, 3, 6, and 12 mo (p < 0.001). 1,25(OH)(2)D concentration increased after 3, 6, and 12 mo of GH (p < 0.05). An increase in urine Ca excretion was observed at 3 and 6 mo (p < 0.05), and the renal threshold for maximum tubular phosphate reabsorption rate (TmPO4/GFR) increased after 1, 3, 6, and 12 mo (p < 0.05). betaCTX concentration increased progressively from 0.74 +/- 0.07 mug/liter at baseline to 0.83 +/- 0.07 mug/liter (p < 0.05) at 1 mo and 1.07 +/- 0.09 mug/liter (p < 0.01) at 3 mo, with no further increase at 6 or 12 mo. PINP concentration increased progressively from baseline (60 +/- 5 mug/liter) to 6 mo (126 +/- 11 mug/liter, p < 0.001), with no further increase at 12 mo. The percentage increase in PINP concentration was significantly higher than betaCTX (p < 0.05). Our study shows that GH has a regulatory role in bone mineral metabolism. GH administration to postmenopausal osteoporotic women improves target organ sensitivity to PTH and bone mineral metabolism and alters PTH secretory pattern with greater increases in bone formation than resorption. These changes, resulting in a net positive bone balance, may partly explain the mechanism causing the increase in BMD after long-term administration of GH in postmenopausal women with osteoporosis shown in previous studies and proposes a further component in the development of age-related postmenopausal osteoporosis.

The Effects of Growth Hormone Administration and Endurance Exercise Training on Insulin Resistance in Sprague-Dawley Rat

This study investigated the effects of endurance exercise on hGH-induced insulin resistance of skeletal muscle in rats. Forty rats were randomly divided into 4 groups: CON (saline injection group, n=10), GH (hGH injection group, n=10), Ex (Exercise group, n=10), GH/Ex (Growth hormone administration/ Exercise group, n=10). GH, GH/Ex animals received hGH by subcutaneous injections (0.4 IU/kg/day, 6 days/week) for 8 weeks and CON, Ex animals received saline injections with the same volume as GH. The exercise regimen was designed in a 8% grade treadmill, 24m/min training speed with 5 times/week. After 8 weeks of treatment, the plasma lipids profiles, triglyceride contents in muscle, muscle glucose transport rates, and OGTT were measured in these rats. After 8-week treatment, plasma Insulin & glucose levels in GH were significantly increased than other 3 groups during OGTT. The rate of glucose transport under submaximal insulin concentrations (1000 uU/ml) was significantly lower in GH being 1.02±0.10 mol/ml/hr as opposed to 1.42±0.12 mol/ml/hr for the CON. However, there was not a significant difference between GH/Ex (1.31±0.10 mol/ ml/hr) and CON. Plasma FFA levels were significantly higher in GH (0.40±0.04 mmol/l), GH/Ex (0.42±0.05 mmol/l) than CON (0.29±0.03 mmol/l). Triglyceride contents in plantaris muscle was significantly greater in GH (0.52±0.06 mol/g) than CON (0.36±0.01 mol/g), Ex (0.39±0.02 mol/g), However GH injection did not significantly affect plasma TC, HDL-C concentrations. In conclusion, regular exercise training attenuates GH-induced insulin resistance in skeletal muscle of rats.

Pelvic ultrasound evaluation in patients with Turner syndrome during treatment with growth hormone.

Treatment with growth hormone (GH), alone or in combination with oxandrolone, is used in patients affected by Turner syndrome to improve growth velocity and adult height. Since GH interacts with gonadotropins in the stimulation of the human ovary, the aim of our study was to evaluate the possible effects of GH administration on uterine and ovarian characteristics. We performed pelvic ultrasound assessment in 29 patients with Turner syndrome aged 7.5-16.6 years (19 with 45,X karyotype; 10 with variant karyotypes) before and during treatment with GH alone. Uterine volume and ovarian size and morphology were compared to those of 23 age-matched girls with Turner syndrome not treated with GH. Both patients and controls were divided into prepubertal and pubertal groups. Cross-sectional and longitudinal studies (before and every 6 months during GH treatment for 2 years) were performed. We observed a significantly higher uterine anteroposterior diameter and volume in younger (< or = 11 years) GH-treated Turner syndrome girls than in those who were untreated. Also visualization and heterogeneous echopattern of the ovaries were significantly more frequent in treated than in untreated Turner syndrome patients, particularly before the age of 11 years. The longitudinal study showed a significant increase in uterine volume, more related to treatment than to age. Spontaneous breast development and menarche were found more frequently in GH-treated Turner syndrome girls. Growth hormone therapy can have a co-gonadotropin role in patients with Turner syndrome.

Body composition and vascular effects of growth hormone administration in old female rats

Aging is associated with alterations in cardiovascular system and changes in body composition. The aim of this study was to investigate the effect of GH on body composition, vascular function and structure in old female rats. Old (20 months) and adult (4 months) female Wistar rats were used. One group of old animals was treated with GH (2 mg/kg/day) for four weeks. Periuterine fat weight, specific gravity index (SGI), dose response to Acetylcholine, Isoprenaline, Phenylephrine and Acetylcholine in the presence of l-NAME and vascular morphology in aortic rings, were studied. Old rats showed increased fat weight and decreased SGI ( p<0.05) as compared to adult animals. GH reduced fat weight ( p<0.05) and tended to increase SGI (NS). Old rats showed impaired vasodilatation to Acetylcholine and Isoprenaline ( p<0.05), and GH improved these responses ( p<0.05). Contraction response to Phenylephrine was higher in old than in adults rats ( p<0.05), but GH did not show any effect. Contraction induced by Acetylcholine+ l-NAME was higher in old rats than in adults, and GH tended to reduce this response, although not significantly. Aortic media area was increased in old rats, and GH reduced this parameter ( p<0.05). In conclusion, GH shows beneficial effects on body composition, vascular function and morphology in old female rats.

Immunomodulatory effects of growth hormone administration are associated with improvement in myocardial contractile performance in dilated cardiomyopathy patients

Immunomodulatory effects of growth hormone administration are associated with improvement in myocardial contractile performance in dilated cardiomyopathy patients

P2173 Anti-remodelling effects of growth hormone administration are associated with the reduction of abnormal peripheral immune responses in dilated cardiomyopathy patients

P2173 Anti-remodelling effects of growth hormone administration are associated with the reduction of abnormal peripheral immune responses in dilated cardiomyopathy patients

Effects of growth hormone administration in human obesity.

To summarize the reports in the literature regarding the effect of growth hormone (GH) treatment of obesity. Clinical trials of GH treatment of obese adults were reviewed and summarized. Specifically, information regarding the effects of GH on body fat and body fat distribution, glucose tolerance/insulin resistance, and adverse consequences of treatment were recorded. GH administered together with hypocaloric diets did not enhance fat loss or preserve lean tissue mass. No studies provided strong evidence for an independent beneficial effect of GH on visceral adiposity. In all but one study, glucose tolerance during GH treatment suffered relative to placebo. The bulk of studies indicate little or no beneficial effects of GH treatment of obesity despite the low serum GH concentrations associated with obesity.

Growth hormone and prevention in elderly patients--fantasy and reality

Human growth hormone is one of the hormones used most frequently in the setting of so-called anti-aging strategies. To date, the preventive value of such a hormone replacement therapy in relatively healthy and well functioning middle aged persons is unknown. Although growth hormone leads to significant alterations in body composition and changes in serum cholesterol levels in patients with adult growth hormone deficiency, there are currently no data supporting the hypothesis that growth-hormone in non deficient persons prolongs life span or reduces morbidity. Aging is associated with a reduction of GH-secretion, serum levels of insulin like growth factor I (IGF-I) and alterations in body composition and function. Based on the many clinical similarities between aging and acquired growth hormone deficiency, several studies have assessed the effects of growth hormone administration in healthy aged women and men. Only a few studies have addressed functional outcomes in a more frail population. These studies suggest that a defined group of older individuals with functional limitation might benefit from GH as a strategy to prevent further functional decline and delay nursing home admission. Because of the lack of proof in frail patients, uncertain long-term effects and high treatment costs GH-administration in the aged should currently be restricted to research questions. Future studies should address the question whether growth hormone alone or in combination with established strategies, such as exercise or improvement in nutrition will serve as a measure to prevent functional decline in frail geriatric patient populations.

Growth hormone treatment increases transmural colonic growth in GH-deficient dwarf rats

Growth hormone (GH) has been implicated as an important factor in the growth regulation of several visceral organs including the gastrointestinal tract. Our aim was to study the effects of GH administration on colonic growth in dwarf rats with an isolated GH deficiency. Dwarf rats were treated with recombinant human growth hormone (rhGH; 2.0 mg/kg/day) for four weeks and compared with saline treated dwarf rats and rats with normal pituitary function. The colonic wall composition was measured by means of stereological techniques. RhGH treatment of the dwarf rats increased body weight by 80% and proximal and distal colon weight by 63% and 90%, when compared with placebo treated dwarf rats (P< 0.01). The weight of the proximal colonic mucosa increased by 83% (P< 0.01), submucosa by 78% (P< 0.05), and the muscularis propria by 51% (P< 0.001) in rhGH treated dwarf rats compared with dwarf controls. The weight of the distal colonic mucosa increased by 88% (P< 0.01), submucosa by 88% (P< 0.05) and the muscularis propria by 58% (P< 0.05) compared with dwarf controls. The growth of mucosa involved all mucosal layers, with a 73 and 92% increase in the proximal and distal colon luminal surface area respectively (P< 0.001, P< 0.01). The food consumption, expressed as g/day/100 g BW was 13% higher in dwarf rats receiving rhGH than in placebo treated rats (P< 0.05) and normal control rats (P< 0.05). When weights of the GI tract compartments are corrected for the increase in body weight the effects of GH treatment were small or non-significant. RhGH administration in GH deficient dwarf rats induces visceral growth with a pronounced increase in colonic luminal surface area and growth of all layers of the colonic wall. These findings confirm the important role of GH in the regulation of intestinal growth.

Body composition in Prader-Willi syndrome: assessment and effects of growth hormone administration.

Children and adults with Prader-Willi syndrome are usually overweight, if not obese. Nevertheless, it is now thought that the body composition exhibited by such individuals is markedly dissimilar to that found in simple obesity. In fact, the body composition typical of Prader-Willi syndrome is actually more characteristic of that found in individuals with growth hormone (GH) deficiency, namely an increased level of adiposity in the limbs in comparison with the trunk and an overall reduction in fat-free mass. This variation in body composition may impact upon the assumptions inherent in many techniques used to measure body size and body composition, such as the use of body mass index and skinfolds. Therefore, it is important that the potential error in body composition assessment is understood by professionals evaluating patients with Prader-Willi syndrome. Accurate assessment of body composition is critical in Prader-Willi syndrome, as a number of recent studies have revealed extremely similar findings relating to the effect of exogenous GH on the body composition of patients with this syndrome. Other notable findings of these studies include significant increases in muscle strength and exercise capacity, which probably result from the changes in body composition. The routine use of exogenous GH to treat this extremely debilitating syndrome should now be considered.

Effects of growth hormone administration on the body composition and hormone levels of genetically fat sheep

AbstractCoopworth sheep selected for low (lean) or high (fat) backfat have large differences in plasma GH profiles. Fat genotype ram lambs (5 months old) were treated with growth hormone (GH) to simulate the plasma GH profiles of lean sheep and investigate whether exogenous GH could modify carcass fatness. For 77 days, bovine GH was administered at 25 Uglkg live weight per day either as a single, daily subcutaneous bolus (fat bolus) or via portable pulsatile infusion pumps (fat pump) which delivered GH solution at 90-min intervals into a jugular catheter. Measurements of body composition were made by computed tomography (CT) and ultrasonic scanning during the trial, with linear carcass measurements and proximate analysis undertaken at the end of the experiment.Before treatments began, mean plasma GH levels were lower (P &lt; 0·01) in fat control (0·34 ugll) than in lean lambs (1·1 μg/l). Several weeks after the start of the trial, mean plasma GH had increased in both fat bolus (1·2 μg/l) and fat pump (0·45 μg/l) treatment lambs with major changes in the pulsatility relative to the fat control lambs. Although these changes were maintained in the fat bolus lambs, by the end of the trial there was no significant difference in mean plasma GH between fat pump and fat control sheep. Throughout the trial, plasma 1GF-1 levels were higher in fat bolus, fat pump and lean lambs than in fat control lambs. Analysis of body composition data over the GH treatment period revealed that the slope of the allometric equation for total fat relative to empty body weight was lower in the fat bolus lambs (1·07) than in the lean lambs (1·50) with fat control and fat pump treatment lambs intermediate (1·30 and 1·36, respectively). Subcutaneous fat was later maturing in lean lambs than in fat control and bolus treatment lambs when regressed against total fat, with the fat pump treatment lambs being intermediate. Linear carcass measurements revealed changes due to GH administration in the distribution of subcutaneous fat and eye muscle dimensions.It is concluded that sheep from the fat genotype show physiological responses to exogenous GH. Increasing plasma GH levels of fat sheep increased plasma IGF-1 and had variable effects on carcass fatness. The change in body composition may be affected by the mode of administration of exogenous GH.

Effects of growth hormone administration on skeletal muscle glutamine metabolism in severely traumatized patients: preliminary report

We have investigated the effects of 24 h human recombinant growth hormone (hGH) administration on leg muscle glutamine exchange and protein kinetics in severely traumatized patients. Muscle amino acid exchange and protein balance were evaluated using the leg arteriovenous balance technique, whereas changes in skeletal muscle free amino acid concentrations were evaluated in biopsy specimens. hGH infusion decreased phenylalanine release from protein degradation by 56 ± 14%, and the rate of branched chain amino acid catabolism by 51 ± 10%. Glutamine release from leg muscle was suppressed by 58 ± 12%. This latter effect was completely accounted for by a hGH-mediated suppression of glutamine synthesis in skeletal muscle. In conclusion, growth hormone administration in trauma patients may restrain protein and amino acid catabolism in skeletal muscle. However, the growth hormone-mediated suppression of glutamine production we have observed in this study could decrease the systemic availability of this amino acid. During growth hormone treatment, this potential side-effect could be prevented by an exogenous glutamine administration.

Effects of Growth Hormone Administration on Muscle and Viscera in Rats Undergoing Compensatory Hypertrophy

Effects of Growth Hormone Administration on Muscle and Viscera in Rats Undergoing Compensatory Hypertrophy

Behavioral and endocrine effects of growth hormone administration in aged female rats.

Growth hormone (GH) secretion declines during normal aging along with reproductive activity in mammalian species. Various behavioral changes also occur in aged animals. In these experiments we have studied the effects of GH administration on behavioral and endocrine alterations exhibited by aged (18 months old) female rats of the Sprague-Dawley strain. Animals were selected showing at least 2 weeks of cornified vaginal smears (constant estrous) and treated with GH (0.1 mg/kg SC) daily for 8 weeks. Vaginal smears performed during the drug treatment revealed a recovery of estrous cycle in 60% of animals. GH treatment was also followed by an increased acquisition of shuttle-box active avoidance behavior and a facilitated retention of passive avoidance response. Compared to saline-injected controls, female rats treated with GH also exhibited a decrease of novelty-induced excessive grooming. The endocrine pattern of GH-treated aged female rats revealed a decrease in plasma prolactin levels and an increase in luteinizing hormone and 17 beta-estradiol levels as compared to those of control animals. These results support the concept that behavioral and endocrine alterations occurring in aging are not irreversible and that GH may interfere with these changes probably by means of its trophic action on different target organs.