Serum Growth Hormone Concentrations Research Articles

Outcome of somatostatin analogue treatment in acromegaly

During the past decade the importance of medical therapy, especially treatment with somatostatin analogues has increased significantly in patients with active acromegaly. Authors analyzed the outcome of somatostatin analogue treatment in acromegalic patients evaluated and followed up at the 2nd Department of Medicine, Faculty of Medicine, Semmelweis University, during the past 10 years. Changes in serum growth hormone (GH) and insulin-like growth factor-1 (IGF-1) concentration, as well as morphologic changes of pituitary adenomas followed by MRI scans were evaluated and compared in 32 acromegalic patients (26 women, 6 men) during long-term somatostatin analogue treatment (mean+/-SE, 3.1+/-0.3 years, range, 1-7 years). Primary somatostatin analogue treatment was applied in 10 patients (7 women and 3 men), whereas 15 patients (14 women and 1 man) had pituitary surgery and 7 patients (5 women and 2 men) underwent both pituitary surgery and irradiation therapy prior to somatostatin analogue treatment. After a 3-month treatment with somatostatin analogues, both serum GH and IGF-1 levels decreased significantly and they remained around the same decreased levels throughout the treatment period. Serum GH decreased from 15.7+/-4.9 to 5.5+/-1.4 ng/ml, and serum IGF-1, expressed as a percentage of the upper limit of age- and sex-adjusted reference value, decreased from 204+/-14% to 135+/-12% at the end of treatment. The efficacy of somatostatin analogue treatment was not influenced by surgical or surgical and irradiation therapies which were applied prior to medical treatment. At the end of treatment 36.7% of patients had safe serum GH (<2.5 ng/ml), while serum IGF-1 returned below the upper limit of age- and sex-adjusted reference range in 41.4% of patients. Pituitary MRI showed regression of the adenoma in 46% of patients, and none of the patients had progression of the pituitary adenoma. Somatostatin analogues are effective therapeutic options for acromegalic patients when primary surgical treatment cannot be performed due to complications and associated disorders, or in patients whose acromegaly remains active after pituitary surgery or after pituitary surgery and irradiation.

Changes in Growth Hormone and Insulin-like Growth Factor-I Levels in the Acute Stage after Open Heart Surgery and at the Time of Discharge

Stress conditions are known to disturb the axis of growth hormone (GH)/insulin-like growth factor-I (IGF-I), but there is little data on this topic after open heart surgery. This study aimed to investigate changes in GH/IGF-I axis in adults undergoing open heart surgery. A total of 162 adult patients admitted for elective major cardiac surgery were studied in a prospective setting. Serum concentrations of GH and IGF-I were measured at four time points: before operation as a baseline, 4 and 12 hours after operation in ICU, and at the time of discharge. Two to 4 venous blood samples were obtained from each patient. To study the changes of GH and IGF-I levels over time, general linear model for repeated measures was applied. Mean age of patients was 51.2+/-14.3 years. Compared with preoperative values (median 0.8, range 0.05-19.4 ng/mL), GH levels rose significantly at four (median 3.3, range 0.1-55 ng/mL) and twelve hours after surgery (median 5.45, range 0.55-61.2 ng/mL), and continued to remain high at the time of discharge (median 2.1, range 0.02-22.7 ng/mL) (p<0.05). Conversely, compared with preoperative levels (173.5+/-89.9 ng/mL), IGF-I decreased at four (140.9+/-66.9 ng/mL) and twelve hours after operation (135.9+/-59.9 ng/mL) and reached its nadir on the day of discharge (114.8+/-43.8 ng/mL) (p<0.01). The patterns of changes in GH and IGF-I over time were significantly different (p<0.01). Adult patients undergoing open heart surgery go through a state of GH resistance characterized by elevated GH and decreased IGF-I levels from the initial hours after operation.

Insulin binding to erythrocyte receptors in acromegalic patients in relation to the activity of acromegaly and to concomitant diabetes mellitus.

Insulin binding to receptors on erythrocytes was studied in patients with acromegaly (n = 27) and in control subjects without any endocrine pathology, diabetes or obesity (n = 13). According to fasting serum concentration of growth hormone (GH), acromegalics were divided into two groups: A) GH less than 10 ng/ml (n = 16) and B) GH above 20 ng/ml (n = 11), in which patients were further divided into subgroups with regard to the presence or absence of diabetes. Insulin binding was decreased both in active and inactive acromegalics when compared with controls. A greater decrease was seen in active acromegaly coupled with diabetes. This was not the case of inactive hyperglycaemic acromegalics, where a compensatory increase in the affinity of "empty" receptors might account for a lack of a greater decrease in insulin binding.

Echocardiographic abnormalities in acromegalic patients.

The aim of our study was the evaluation of the cardiac size and left ventricular function in 26 patients with acromegaly and 20 control subjects using echocardiography. The following parameters were evaluated: systolic and diastolic ventricular dimensions, diastolic posterior wall and interventricular septal thickness, left ventricle ejection fraction and left ventricular mass, amplitude of the posterior left ventricular wall movement, speed of the circular fibres shortening area of the left ventricular muscle and left ventricular contractility index. In 91% of patients with acromegaly echocardiographic abnormalities were found. The most frequent were: concentric thickening of the left ventricular posterior wall in 38%, interventricular septal thickening in 54% and increased left ventricular mass in 84.6% of acromegalic patients. Left ventricular dimensions were increased: diastolic in 65.4% and systolic in 92% of patients. In 46% of cases the ejection fraction was decreased. There was no correlation between extent of the left ventricular hypertrophy and other echocardiographic abnormalities, serum growth hormone concentration, choice of therapy and duration of the disease.

Hormonal and metabolic responses to slow movement resistance exercise with different durations of concentric and eccentric actions

We examined hormonal responses to slow movement exercise involving concentric (CON) and eccentric (ECC) actions. Nine men performed knee extension exercises: (1) low-intensity exercise with slow CON contractions (5-1; 5 s for CON and 1 s for ECC); (2) low-intensity exercise with slow ECC contractions (1-5; 1 s for CON and 5 s for ECC); (3) low-intensity exercise with slow CON and ECC contractions (3-3; 3 s for each contraction); and (4) high-intensity exercise at normal velocity (1-1; 1 s for each contraction). Lactate concentration was significantly higher after the 5-1 than after the 1-5 (P < 0.05). Slow movement exercises significantly raised the concentrations of plasma epinephrine, serum growth hormone, and free testosterone (P < 0.05). Serum growth hormone concentration increased to a greater extent after the three slow movement trials compared with the normal movement trial (1-1). However, serum cortisol concentration was significantly higher after the 5-1 than after the 1-5 and 1-1 (P < 0.05). Average V(O)(2) throughout the exercise session (divided by the time to complete exercise session) was significantly higher in the 1-1 (P < 0.05), with no significant difference among the slow movement trials. In conclusion, low-intensity exercises with slow movement acutely increased anabolic hormone concentrations regardless of the time to complete CON and ECC actions. In contrast, low-intensity exercise with slower ECC action stimulated smaller changes in lactate and cortisol compared with low-intensity exercise with slower CON action.

Breast-tissue composition and other risk factors for breast cancer in young women: a cross-sectional study

Mammographic density is a heritable quantitative trait and is a strong risk factor for breast cancer in middle-aged and older women. However, little is known about the development of mammographic density in early life. We used MRI to measure the water content of the breast, which provides a measurement of the fibro-glandular content of breast tissue with similar accuracy to mammography, but without the attendant exposure to radiation. Between December, 2003, and December, 2007, we recruited 400 young women, aged 15-30 years, and their mothers. We used MRI scans to measure daughters' breast water and fat, and on the same day obtained blood for hormone assays in the follicular phase of the menstrual cycle for each young woman. Mothers underwent mammography (n=356), and a random sample (n=100) also consented to have a breast MRI scan. In mothers, per cent water-as measured by MRI-was strongly correlated with per cent mammographic density (r=0.85). Per cent water in daughters (median 44.8%) was significantly higher than in mothers (median 27.8%; p<0.0001), and was independently inversely associated with both their age (p=0.04) and weight (p<0.0001), and positively associated with their height (p<0.0001) and their mothers' per cent mammographic density (p<0.0001). Serum growth hormone concentrations, adjusted for covariates, were positively associated with per cent breast water (p=0.001) in a subgroup of young women (n=280) who had not used oral contraceptives within 6 months. Per cent breast water was greatest during the ages when women are most susceptible to breast carcinogens, and was associated with weight, height, and mother's breast-tissue characteristics, and with serum concentrations of growth hormone: a breast mitogen that also mediates postnatal somatic growth. Mammographic density in middle age might partly be the result of genetic factors that affect growth and development in early life. Canadian Breast Cancer Research Alliance.

Effects of repeated whole-body cold exposures on serum concentrations of growth hormone, thyrotropin, prolactin and thyroid hormones in healthy women

Cold therapy is used to relieve pain and inflammatory symptoms. Humoral changes may account for the pain alleviation related to the cold exposures. The aim of the present study was to examine the effects of two types of cold therapy, winter swimming in ice-cold water (WS) and whole body cryotherapy (WBC), on the serum levels of the growth hormone, prolactin, thyrotropin and free fractions of thyroid hormones (fT3, fT4). One group of healthy females ( n = 6) was exposed to WS (water 0–2 °C) for 20 s and another group ( n = 6) to WBC (air −110 °C) for 2 min, three times a week for 12 weeks. Blood samples used for the hormone measurements were taken on weeks 1, 4 and 12 before and 35 min after the cold exposures and on the days of the respective weeks, when the cold exposures were not performed. During the WS treatments, serum thyrotropin increased significantly at 35 min on weeks 1 ( p < 0.01) and 4 ( p < 0.05), but the responses were within the health-related reference interval. During the WS, the serum prolactin measured at 35 min on week 12 was lower than during the control treatment, and no changes in fT3 or fT4 were observed. During the WBC, no changes in the serum levels of the studied hormones were observed during the 12 weeks. In conclusion, repeated WS and WBC treatments for healthy females do not lead to disorders related to altered secretions of the growth hormone, prolactin, thyrotropin, or thyroid hormones.

Influence of Gender on Serum Growth Hormone, Insulin-Like Growth Factor-I and Its Binding Protein-3 during Aging

PurposeThe serum concentrations of insulin-like growth factors-I (IGF-I), insulin-like growth factor binding protein-3 (IGFBP-3) and growth hormone (GH) are related to body composition, function and metabolism, and are influenced by the aging process. This study was to investigate the influence of gender on serum concentrations of IGF-I, IGFBP-3 and GH in middle and old age subjects.Materials and MethodsSixty healthy volunteers (male 35, female 25, 36-70 years) were divided into ≤ 50 and > 50 years groups, based on gender. Women > 50 years were post-menopause. IGF-I, IGFBP-3, and GH were determined by immunoradiometric assay.ResultsIGF-I was shown to be negatively correlated with age (women r = -0.62, p < 0.001; men r = -0.38, p < 0.05), whereas there was no correlation between IGF-I and GH values. Women > 50 years showed a significant reduction in IGF-I values than women ≤ 50 years (p < 0.01). Women > 50 years showed smaller IGF-I/IGFBP-3 molar ratios (0.177998 ± 0.039404) than men of same age group (0.228326 ± 0.050979, p < 0.01) and women ≤ 50 years (0.247667 ± 0.069411, p < 0.01). Age was shown to positively correlate with GH/IGF-I (r = 0.49, p < 0.05) and GH/IGFBP-3 ratios (r = 0.40, p < 0.05) in women.ConclusionsThe influence of aging on serum concentrations of IGF-I is more remarkable in women than in men. Menopause causes reduction of IGF-I/IGFBP-3 molar ratio. Women have the trend of progressive hypoactivity of GH to stimulate IGF-I and IGFBP-3 secretions with age.

Acromégalie

Acromegaly is a rare disease usually caused by growth hormone (GH) hypersecretion, due to a pituitary adenoma; in very rare cases, acromegaly is due to ectopic secretion of GHRH, responsible for pituitary hyperplasia. Owing to its insidious onset, acromegaly is often diagnosed late (4 to > 10 years after onset), at an average age of about 40 years, in front of an acquired, slowly progressing disfigurement mainly involving the face and extremities. Acromegaly has also rheumatologic, cardiovascular, respiratory and metabolic consequences which determine its prognosis. The diagnosis is based on an increased serum GH concentration unsuppressed following an oral glucose load (oral glucose tolerance test -OGTT-) and an increased insulin-like growth factor-I (IGF-I); according to a 2000 Consensus statement, if the basal serum GH is above 0,4microg/L (1.2mIU/L) and/or if the IGF-I is elevated, an OGTT must be performed. If the lowest GH value (nadir) during OGTT remains above 1microg/L (3mIU/L), acromegaly is confirmed. With the generalized use of very sensitive assays nowadays, it has recently been considered that this cutoff should be decreased to 0,3microg/L (0.9mIU/L). Treatment is aimed at correcting (or preventing) tumor compression by excising the culprit lesion, and at reducing GH and IGF-I levels to normal values (or at least to a "safe" GH level of < 2microg/L or < 6mIU/L). A stepwise therapeutic strategy is used: transsphenoidal surgery is often the first-line treatment; when surgery fails to correct GH/IGF-I hypersecretion, medical treatment with somatostatin analogs and/or radiotherapy can be used, somatostatin analogs being generally preferred; the GH antagonist (pegvisomant) is used in patients that are resistant or intolerant to somatostatin analogs. Prognosis of acromegaly has improved in the recent years: adequate hormonal disease control is achieved in most cases, allowing life expectancy similar to that of the general population.

Acute GH and IGF-I responses to short vs. long rest period between sets during forced repetitions resistance training system

In order to examine the effects of different rest intervals between the sets on acute growth hormone (GH) and insulin-like growth factor-1 (IGF-I) responses, ten recreationally resistance trained men served as subjects (Mean ± SD, age=22 ± 2 years, body mass= 84 ± 8 kg). Subjects performed two heavy-resistance training protocols that were similar with regard to the total volume of work (sets x reps x loads), but differed with regard the length of rest between sets (1vs.3-minutes). Both protocols included 5 sets of 10 RM bench press and squat that performed on two randomized separate sessions. Blood samples were collected before, immediately after and 1-hour after the protocols for determination GH, IGF-I and blood lactate concentration. Postexercise values for lactate and GH were significantly (P£0.05) elevated above preexercise, but did not for IGF-1 concentrations. However, IGF-1 serum concentrations were significantly (P£0.05) increased during 1-hour postexercise. Postexercise serum GH and blood lactate concentrations were significantly (P£0.05) higher in SR than LR protocol, but IGF-1 did not change. These data suggest that the duration of the rest interval between sets of dynamic resistance exercise influence GH serum concentration, it must be noted that short rest period between sets induced greater acute GH responses than the long rest period. Given that GH concentration is an anabolic hormone, this finding may have implications regarding hypertrophy in resistance training. Keywords: Growth hormone; Insulin-like growth factor-1; Resistance training; Rest between sets. South African Journal for Research in Sport, Physical Education and Recreation Vol. 30 (2) 2008: pp. 31-38

Effects of Milk Replacer Composition on Selected Blood Metabolites and Hormones in Preweaned Holstein Heifers

We investigated the effects of increasing dietary protein and energy on concentrations of selected blood metabolites and hormones in Holstein heifers. Twenty-four heifers were fed 1 of 4 milk replacer (MR) diets for 9 wk (n=6/diet): control [20% crude protein (CP), 21% fat MR fed at 441g of dry matter (DM)/d], HPLF (28% CP, 20% fat MR fed at 951g of DM/d), HPHF (27% CP, 28% fat MR fed at 951g of DM/d), and HPHF+ (27% CP, 28% fat MR fed at 1,431g of DM/d). Heifers were fed twice daily; water and starter (20% CP, 1.43% fat) were offered free choice and starter orts recorded daily. Serum and plasma aliquots from blood samples collected twice weekly after a 12-h fast were analyzed for insulin-like growth factor (IGF)-I, IGF-binding proteins (IGFBP), growth hormone (GH), insulin, glucose, nonesterified fatty acids, triglyceride, and plasma urea nitrogen concentrations. Only plasma glucose, IGFBP-2, and IGFBP-3 were affected by diet. Dietary treatment differences were only noted when the control was compared with the average of the other 3 diets. The addition of fat to the MR (HPLF vs. HPHF) and increased volume of MR (HPHF vs. HPHF+) had no effect on plasma glucose concentration or relative abundance of IGFBP-2 or IGFBP-3. Heifers fed the control diet had less glucose, greater IGFBP-2, and less IGFBP-3 than the average of the other 3 diets. There was a diet by week interaction for IGF-I. Serum IGF-I concentration in control heifers varied in a quadratic manner with a nadir (20±4ng/mL) at wk 4, whereas IGF-I increased linearly in heifers on other diets. Both insulin and triglyceride changed over time in a complex pattern (significant linear and quadratic contrast effects). The greatest concentrations were measured at wk 0.5 with nadirs at wk 6 for both insulin and triglyceride. Serum GH concentration decreased in a linear manner from wk 0.5 to wk 9 in all heifers. Relative abundance of IGFBP-2 was quadratic over time with the greatest amount of IGFBP-2 observed at wk 5. With the exception of glucose, IGF-I, IGFBP-2, and IGFBP-3, the blood variables measured were not influenced by treatment. The IGF-I –GH–IGFBP axis requires further study in heifers to deduce effects of nutrition on hypothalamic regulation of metabolism. We expected to see more treatment differences in concentrations of metabolites involved with protein and fat metabolism. It is likely that the diets used in this study were not diverse enough in composition to elicit such changes or that the efficiency of use of absorbed protein and fat was not different in these animals.

Acromegaly

Acromegaly is an acquired disorder related to excessive production of growth hormone (GH) and characterized by progressive somatic disfigurement (mainly involving the face and extremities) and systemic manifestations. The prevalence is estimated at 1:140,000–250,000. It is most often diagnosed in middle-aged adults (average age 40 years, men and women equally affected). Due to insidious onset and slow progression, acromegaly is often diagnosed four to more than ten years after its onset. The main clinical features are broadened extremities (hands and feet), widened thickened and stubby fingers, and thickened soft tissue. The facial aspect is characteristic and includes a widened and thickened nose, prominent cheekbones, forehead bulges, thick lips and marked facial lines. The forehead and overlying skin is thickened, sometimes leading to frontal bossing. There is a tendency towards mandibular overgrowth with prognathism, maxillary widening, tooth separation and jaw malocclusion. The disease also has rheumatologic, cardiovascular, respiratory and metabolic consequences which determine its prognosis. In the majority of cases, acromegaly is related to a pituitary adenoma, either purely GH-secreting (60%) or mixed. In very rare cases, acromegaly is due to ectopic secretion of growth-hormone-releasing hormone (GHRH) responsible for pituitary hyperplasia. The clinical diagnosis is confirmed biochemically by an increased serum GH concentration following an oral glucose tolerance test (OGTT) and by detection of increased levels of insulin-like growth factor-I (IGF-I). Assessment of tumor volume and extension is based on imaging studies. Echocardiography and sleep apnea testing are used to determine the clinical impact of acromegaly. Treatment is aimed at correcting (or preventing) tumor compression by excising the disease-causing lesion, and at reducing GH and IGF-I levels to normal values. Transsphenoidal surgery is often the first-line treatment. When surgery fails to correct GH/IGF-I hypersecretion, medical treatment with somatostatin analogs and/or radiotherapy can be used. The GH antagonist (pegvisomant) is used in patients that are resistant to somatostatin analogs. Adequate hormonal disease control is achieved in most cases, allowing a life expectancy similar to that of the general population. However, even if patients are cured or well-controlled, sequelae (joint pain, deformities and altered quality of life) often remain.

Efeitos do intervalo de recuperação entre séries de exercícios resistidos no hormônio do crescimento em mulheres jovens

O objetivo deste estudo foi examinar as respostas agudas de três diferentes intervalos de recuperação entre séries, durante uma sessão tradicional de exercícios resistidos para membros inferiores em mulheres jovens. Participaram deste estudo doze mulheres aparentemente saudáveis e treinadas em exercícios resistidos (26,83 ± 3,93 anos). Em três momentos distintos, os sujeitos realizaram em ordem contra balanceada, o protocolo de exercícios resistidos para membros inferiores com 30 (P30), 60 (P60) ou 120 (P120) segundos de intervalo de recuperação entre séries. A sessão de exercícios resistidos consistia de quatro exercícios para os membros inferiores (cadeira extensora, agachamento, mesa flexora e leg press), com 3 séries de 10 repetições e carga de 10 repetições máximas (RM). Coletas sangüíneas foram realizadas para determinar as concentrações do hormônio do crescimento (GH) antes do exercício (T0), imediatamente após cada sessão de exercício (T1), e 5 (T5), 15 (T15) e 30 (T30) minutos de recuperação. A avaliação estatística dos dados foi por meio da análise de variância de medidas repetidas 3 X 5 [intervalo de recuperação (30s, 60s, 120s) X tempo (T0, T1, T5, T15, T30)], com o teste post-hoc Least Significant Difference (LSD). O nível de significância estatístico utilizado foi p &lt; 0,05 em todas as comparações. Não houve diferenças entre os protocolos (P30, P60 e P120) nas concentrações sanguíneas do GH em repouso. Porém, em relação a T0, todos os protocolos obtiveram aumentos significativos (p &lt; 0,05) nas concentrações do GH após a sessão de exercícios. As concentrações do GH entre os protocolos foram significativamente maiores para o P30 (24,34 ng/ml) e P60 (23,07 ng/ml) quando comparadas ao P120 (17,13 ng/ml) em T1. A concentração do GH no P30 foi significativamente maior em T5, T15 e T30, quando comparada ao P60 e ao P120. A magnitude das respostas hormonais (GH) agudas em mulheres treinadas parece ser maior com 30s de intervalo entre séries quando comparada com intervalos mais longos (60 ou 120s).

Effect of a Pre-Exercise Energy Supplement on the Acute Hormonal Response to Resistance Exercise

The effect of a pre-exercise energy sport drink on the acute hormonal response to resistance exercise was examined in eight experienced resistance trained men. Subjects were randomly provided either a placebo (P: maltodextrin) or the supplement (S: combination of branched chain amino acids, creatine, taurine, caffeine, and glucuronolactone). Subjects performed 6 sets of no more than 10 repetitions of the squat exercise at 75% of their 1 repetition maximum (1RM) with 2 minutes of rest between sets. Blood draws occurred at baseline pre-exercise, immediately post- (IP), 15 minutes post- (15P), and 30-minutes post (30P) exercise for measurement of serum growth hormone, total and free testosterone, cortisol, and insulin concentrations. Although significant differences were seen only at set 5, the total number of repetitions and training volume tended (p = 0.08) to be higher with S compared to P. Serum growth hormone and insulin concentrations were significantly higher at 15P and IP, respectively, in S compared to P. Results suggest that a pre-exercise energy S consumed 10 minutes before resistance exercise can enhance acute exercise performance by increasing the number of repetitions performed and the total volume of exercise. The enhanced exercise performance resulted in a significantly greater increase in both growth hormone and insulin concentrations, indicating an augmented anabolic hormone response to this pre-exercise S.

The role of pegvisomant in the treatment of acromegaly

Background: Expert surgery in acromegaly is curative in about only 60% of cases. Postsurgical radiation therapy is associated with a high incidence of hypopituitarism and its effect on growth hormone decrease is slow. Therefore, effective adjuvant medical treatment is mandatory. Objective: To delineate the role of pegvisomant in the treatment of acromegaly. Methods: A search of the Medline, Embase and Web of Science databases for clinical studies on pegvisomant was performed. In addition, abstracts of the major endocrine society meetings in 2007 were searched. Results: When treatment with somatostatin analogues after non-curative surgery does not lead to normalisation of serum IGF-I and growth hormone concentrations, pegvisomant alone or in combination with somatostatin analogues can control disease in a substantial number of patients. The most important side effects are disturbed liver function tests and, rarely, growth of the adenoma. The efficacy in non-operated patients and the long-term safety have yet to be ascertained.

Rice protein concentrate partially replaces dried whey in the diet for early‐weaned piglets and improves their growth performance

AbstractBACKGROUND: Recently, rice protein concentrate (RPC), a much cheaper source of dietary protein, has become commercially available for use in the feed industry. Importantly, dietary supplementation with RPC can increase feed intake by early‐weaned pigs. The objective of this study was to determine whether RPC can replace milk protein in the diet for early‐weaned pigs.RESULTS: Neither average daily gain (ADG), average daily feed intake (ADFI), nor the feed/gain ratio differed among the treatment groups in weeks 1 and 2. In week 3, the addition of 5 or 10% RPC to diets increased (P &lt; 0.05) ADFI and ADG of pigs compared to those in the control group fed a 60% dried whey diet. During the entire 21‐day trial, ADFI and ADG were greater (P &lt; 0.05) in pigs fed the 5 and 10% RCP diets than in pigs fed the 60% dried whey and 15% RCP diets. There were no differences in the serum concentrations of growth hormone on days 14 and 21, serum concentrations of insulin growth factor‐I (IGF‐I) on day 14, or IGF‐I gene expression in liver and skeletal muscle on days 14 and 21 among the dietary treatments. Serum concentrations of IGF‐I in pigs fed the 5, 10 and 15% RPC diets were greater than those in pigs fed the 60% dried whey diet.CONCLUSION: Findings indicate that up to 10% RPC can be used to replace dried whey in the diet for 7‐ to 21‐day‐old weaned piglets and can improve their growth performance. Copyright © 2008 Society of Chemical Industry

Neonatal programming of skeletal development in sheep is mediated by somatotrophic axis function

Nutritional and metabolic exposure during critical periods of prenatal and neonatal development in animals and humans may induce long-term effects on health status in later life. The aim of this study was to investigate the effects of neonatal treatment with beta-hydroxy-beta-methylbutyrate (HMB) during the first 3 weeks of life on programming of skeletal development in sheep. The study was performed on 12 male sheep divided into two groups. While the control group was treated with placebo, the lambs in the HMB group received the calcium salt of beta-hydroxy-beta-methylbutyrate at a daily dose of 0.1 g (kg body weight)(-1). The assessment of growth hormone (GH), insulin-like growth factor-1 (IGF-1) and biochemical bone turnover markers in serum was performed in 21- and 130-day-old animals. Post mortem, volumetric bone mineral density, morphological and mechanical properties were determined in femur and lumbar vertebrae. Neonatal treatment with HMB increased serum concentrations of bone-specific alkaline phosphatase, osteocalcin, GH and IGF-1 in 21-day-old lambs by 125.2, 93.8, 71.8 and 70.9%, respectively (P < or = 0.05). The C-terminal telopeptide of type I collagen (CTX) concentration was increased in 130-day-old animals from the HMB group by 33.1% (P = 0.03). Furthermore, HMB administration improved bone weight, volumetric bone mineral density and bone morphological and mechanical properties of femur and lumbar spine. In conclusion, this study showed long-term beneficial effects of neonatal treatment with HMB on programming of peripheral and axial skeleton properties that were mediated by a transient improvement of somatotrophic axis function and acceleration of bone metabolism.

Effects of rest duration between sets of resistance training on acute hormonal responses in trained women

This study investigated the acute hormonal response to three different rest periods between sets of a traditional lower body resistance training session in young women. Twelve healthy trained females (26.83+/-3.93 years) participated in the study. On three separate sessions of a lower body resistance exercise protocol, subjects were assigned in a random order a rest interval of 30s (P30), 60s (P60) or 120s (P120) between sets. The resistance exercise session consisted of four lower body exercises with three sets performed until contractile failure using 10-repetition maximum (RM) load. Blood samples were drawn for determination of serum growth hormone (GH) and cortisol concentrations before exercise (T0), immediately after each training session (T1), and after 5min (T5), 15min (T15), and 30min (T30) of recovery. Statistical evaluation of the area under the time-concentration relationship for GH (GHauc) and for cortisol (Cauc) were analyzed using a one-way ANOVA There were no differences among protocols (P30, P60 and P120) in the serum GH and cortisol concentrations at baseline (T0). However, as compared to T0, all protocols led to acute increases (p<0.05) in serum GH concentrations after each training session. The GHauc was greater for P30 than for both P60 and P120, however, there were no differences between P60 and P120. The Cauc were not different among protocols. Thus, the magnitude of acute GH responses in previously strength-trained women appears greater with a 30-s rest interval between sets compared to longer rest periods of 60- or 120-s.

Neuropeptide W Influences the Excitability of Neurons in the Rat Hypothalamic Arcuate Nucleus

Neuropeptide W (NPW) is a ligand of the recently deorphaned receptor GPR7. Intracerebroventricular injection of this peptide results in reduced serum growth hormone concentration. Using whole-cell patch clamp recordings from somatostatin (SS) neurons in the hypothalamic arcuate nucleus, identified post-hoc using single-cell RT-PCR, we investigated the effects of NPW on membrane excitability. NPW application in acute slices of the arcuate nucleus resulted in the depolarization of the majority (62.5%) of the SS neurons tested, while smaller proportions of cells showed hyperpolarization or no response. Both the depolarization and hyperpolarization of arcuate SS neurons were preserved during recordings where voltage-gated sodium channels were blocked with tetrodotoxin, suggesting direct effects of NPW on the excitability of SS neurons. The observed depolarization of the majority of the SS neurons tested suggests that the central effects of NPW to inhibit growth hormone release results from activation of arcuate SS neurons, which could result in an inhibition of GHRH-releasing neurons.

Nouveaux mécanismes moléculaires impliqués dans l’insensibilité à l’hormone de croissance

Growth hormone (GH), secreted by the anterior pituitary into the circulation, binds to membrane receptors in target tissues to stimulate body growth; most of its effects is mediated by the insulin-like growth factor 1 (IGF-1). In addition to promoting growth, GH has important metabolic actions. The syndrome of GH insensitivity (GHI) was first identified in 1966 by Laron et al. in three children with clinical phenotype characteristic of growth hormone deficiency but associated with elevated serum concentration of GH. Direct evidence of a GH receptor (GHR) abnormality was provided in 1989. More recently, molecular abnormalities in the postreceptor signalling mechanism were found. Mutations of signal transducer and activator of transcription 5b (Stat5b) were reported in patients with growth retardation and primary immunodeficiency. Mutations of the tyrosin phosphatase Shp2 were identified in patients affected by Noonan syndrome characterized by short stature, cardiopathy and increased risk of leukaemia. The unmasking of the molecular bases for these defects will contribute greatly to our future understanding of both normal and aberrant growth. Moreover, this knowledge should bring insight on cancerogenesis or immunodeficiency caused by cytokines resistance.