Growth Hormone Values Research Articles

Gender Differences in Diurnal Growth Hormone and Epinephrine Values in Young Adults during Ambulation

In the present study, the impact of gender, oral contraceptives, and ambulation on serum growth hormone (GH) and urinary catecholamines was examined in healthy young adults. Twenty-one medical student volunteers--7 men, 7 women, and 7 women taking oral contraceptives--were investigated. Serum samples were drawn every second hour during a 24-h period. At 0800 the first morning, serum samples were drawn while subjects were in the ambulatory state; the next morning, serum samples were drawn at 0800 while the subjects were still resting in bed. During the daytime, GH concentrations were sevenfold higher in the women than in the men, a difference larger than described previously. During the night, there was no gender difference. In the morning, ambulatory GH concentrations were 28-fold higher in the women than in the men, whereas supine GH concentrations were only 4.6-fold higher in the women than in the men. Daytime urinary output of epinephrine was lower in the women than in the men, whereas there was no difference at night. Women using estrogen-containing oral contraceptives had lower epinephrine and higher GH values than women not taking oral contraceptives. In women, morning GH concentrations were higher in the ambulatory than in the resting state, whereas they were lower in the ambulatory state than in the resting state in men. The secretion of GH and epinephrine is gender-dependent and differs during the daytime in a reciprocal manner, with higher GH and lower epinephrine in women than in men. Oral contraceptives appear to further increase such differences. It seems likely that the data reflect a gender difference in the utilization of substrates for energy production.

The impact of gender, puberty and body mass on reference values for urinary growth hormone (GH) excretion in normally growing non-obese and obese children.

There is a lack of normal reference data on urinary GH (u-GH) excretion in children. We have investigated the impact of age, gender, pubertal development and body mass on reference values for u-GH excretion in normally growing non-obese and obese children. u-GH levels were evaluated in 1153 healthy normal children (aged 5-14) and in 684 obese children (body mass index, BMI: > 75th). u-GH levels (ng/8 h) were determined by ELISA as the mean value of three consecutive first morning voidings. Reference values (5-95th centile) for u-GH excretion in obese and non-obese children of both sexes are reported. In normal prepubertal children median u-GH levels were relatively stable and superimposable in the two sexes; subsequently, u-GH levels increased, reaching a peak value at 13 years in both sexes. Significant increments (P < 0.0001) in u-GH levels were shown at B2 for females and at G3 for males. A slight decline was evident at 14 years. In obese children, median u-GH concentrations were significantly lower than those recorded in normal children of prepubertal age and at all stages of puberty (except in females at B2), in spite of their comparable normal height. u-GH levels significantly increased at puberty also in obese children, although the pubertal rise was significantly (P < 0.001) lower (1.7-fold in both sexes) than that observed in normal children (2.5-fold in boys and 2.3-fold in girls). A multiple regression analysis showed that both chronological age (beta: 0.20), BMI (beta: - 0.11), gender (beta: - 0.04) and pubertal stage (beta: 0.25) contributed significantly to the physiological variation in u-GH levels (multiple R: 0.44, P < 0.00001). This study provides reference values for u-GH in normally growing non-obese and obese children, analysing the impact of gender, puberty and body mass on this parameter. In agreement with previous studies, which demonstrate blunted GH-responses to provocative stimuli and reduced nocturnal GH concentration, obese children have significantly lower u-GH levels than age-matched normal weight children, both before and during puberty.

Outcome of transphenoidal surgery for acromegaly and its relationship to surgical experience.

A number of surgical series have been reported on the treatment of acromegaly and their results vary widely. The acceptable definition of remission has changed in recent years and it is known, though in a small series, that growth hormone levels of > 5 mU/l are still associated with an increased mortality from the condition. We have analysed data at this centre and examined the outcome of transphenoidal surgery for acromegaly, compared our results with recently published series from other centres and also assessed factors which might effect outcome including whether there is any demonstrable effect of the experience of the surgeon on outcome. We have analysed data from all of our 139 patients in whom follow up data are available who have undergone initial transphenoidal surgery for acromegaly by one surgeon at this centre, between 1974 and 1995. Follow up was for a median of 5 years (range 1 month to 17 years). 67% of patients achieved the criterion for remission (mean GH < 5 mU/l). Success was related to tumour size and preoperative growth hormone values. Thus 91% of patients with microadenomas were in remission postoperatively compared to 46% of patients with macroadenomas. Analysis of the results according to the year of operation showed an improvement in success rates with time. More than 15 years ago, the success rate according to the growth hormone criteria set was 48% and the failure rate 52%. In contrast in the last 5 years analysed, the overall success rate was 74% with a failure rate of 26% (P < 0.04). The success rate for microadenomas was 50% initially, then remained 100%. The case mix was analysed and no change was found. We have also demonstrated an improvement in pituitary function (including normalization of preoperative elevated prolactin) with time so that pre 1981 16% of patients' pituitary function improved perioperatively but 10 years later this figure had risen to 34% (P < 0.03). There was no change over time in the development of pituitary hypofunction, complication rate or recurrence rate. Surgical treatment is a safe and effective treatment for acromegaly and remains the first choice of treatment for most acromegalic patients. The results of this centre compare favourably with series from other centres. We have demonstrated improved results, both in terms of post operative growth hormone values and pituitary function tests with time and increasing neurosurgical experience. We conclude that outcome for the surgical treatment for acromegaly is best achieved with one surgeon specialising in pituitary surgery. Improved operative outcome thus achieved has major cost implications and avoids the necessity for consideration of postoperative radiotherapy and the use of expensive growth hormone suppressing drugs in the postoperative period.

Influence of Gender in Growth Hormone Status in Adults: Role of Urinary Growth Hormone

A recent paper by Engstrom et al. (1) presented marked gender differences in plasma growth hormone (GH) values in young adults (21–26 years of age), evaluated in the consulting room and after overnight fasting. The authors observed higher values in the women than in the men. They proposed that something in the morning triggers a GH burst in almost all of the women but in very few of the men. Veldhuis in the 24th International Symposium in Antwerp ( GH and Growth Factors in Endocrinology and Metabolism , October 1997; information printed by Sterling Press, UK, for Pharmacia & Upjohn) affirmed that gender itself has a major impact on the secretion of GH in adults. Unfortunately, until now the basis of sexual dimorphism in GH secretory patterns/status in humans has not fully understood. However, several works suggest that estrogens play an important role in GH secretion in women compared with men. Lang et al. (2) observed a difference in response to growth hormone-releasing hormone (GHRH) in premenopausal, but not postmenopausal, women compared with men. Therefore, estrogens seem to increase …

Six-hour and four-hour nocturnal sampling for growth hormone.

Overnight sampling for growth hormone (GH) is a research tool for quantifying characteristics of spontaneous GH secretion. However, the study is costly in assays and blood volume, particularly that required from a small child. Existing overnight GH data from 126 normal children and from 227 children with GH deficiency or short stature were reanalyzed, examining 6-h and 4-h segments of this data for accuracy in representing each child's 12-h GH secretion. The goal was to see whether the test could be made shorter and more practical without losing accuracy. The 6-h segment 2200-0400 h consistently contained the majority of GH peaks. Correlation was high between GH values from 2200-0400 h and from the 12-h period. Normal 95% confidence limits (CL) for GH during 2200-0400 h were derived from data in normal children for gender and each pubertal stage. Data from short children were compared with the normal 6-h 95% CL. In short children, GH values low for 12-h were also low for 6-h. Only a few children with normal 12-h values (1.5% of normals, 0.5% with short stature) had GH values outside 95% CL for 6-h. Six-hour GH sampling (2200-0400 h) is accurate and cost-efficient compared to the 12-h overnight GH study. These studies are primarily useful in research settings.

Insulin-like growth factor-I and insulin-like growth factor binding protein-3 serum levels in ankylosing spondylitis.

Low bone mass, vertebral osteopenia and fractures have been described in patients with ankylosing spondylitis (AS), but the aetiology of this osteoporosis (OP) remains unknown. Insulin-like growth factor-I (IGF-I), a bone-promoting peptide, may be considered as reflecting osteoblast function as well as its main binding protein, insulin-like growth factor binding protein-3 (IGFBP-3). Both were found to be decreased in post-menopausal women and male patients with idiopathic OP. In this study, we aimed to measure the circulating IGF-I and IGFBP-3 in AS patients. Thirty-three AS patients were compared to 23 healthy controls. Bone mineral density (dual X-ray absorptiometry) was measured at the spine and the femoral neck. We determined the serum levels of growth hormone (GH), insulin, glycaemia, and the IGF-I and IGFBP-3 serum concentrations. A lowered lumbar spine bone mineral density was found in the AS group (AS: 0.946 g/cm2, controls: 1.02 g/cm2; P = 0.05). AS patients had a higher glycaemia than controls, but results were in the normal range. There were no significant differences in the mean values for GH and insulin. Mean IGF-I serum levels were 218.3 ng/ml (+/-72.4) in patients and 212.1 (+/-71.1) in controls (P = 0.75). The serum concentrations of IGFBP-3 were significantly lower in AS (3.29+/-0.6 microg/ml) than in healthy subjects (3.63+/-0.6 microg/ml; P = 0.05). There was a negative correlation between the serum IGFBP-3 concentration and erythrocyte sedimentation rate (r = -0.39; P = 0.025). Since IGFBP-3 is an important cofactor for IGF-I and modulates its bioavailability and activity in bone, these data suggest that osteoblast cell function could be impaired in AS. Inflammation could play a role in this IGFBP-3/IGF-I axis involvement. However, further studies are warranted to determine the role of the other growth factors and their binding proteins in the OP of AS.

Anabolic Effects of Growth Hormone Treatment in Young Children with Cystic Fibrosis

Background: Malnutrition is commonly found in children with Cystic Fibrosis (CF) and is characterized by poor weight gain and linear growth. Almost one-third of children with CF are below 5th percentile for weight and height. Intensive nutritional supplementation may not result in sustained improvement in weight gain and linear growth.Objective: To evaluate the anabolic effects of GH, Humatrope (Eli Lilly, 0.05 mg/kg/day) was administered to five children with CF (3 males/2 females) for an average period of 2 years.Methods: All patients were maintained on caloric intake of 1.3–2.0 times the recommended daily allowance. Patients underwent standard growth hormone (GH) stimulation studies and measurement of IGF-1 and IGFBP-3.Results: The mean ± SE for age and skeletal age were 3.2 ± 0.85 years and 2.0 ± 0.45 years, respectively. Growth was assessed by determining both weight and height, which were normalized for age and sex by calculating Z scores using HANES I reference data. Differences in Z scores between clinic visits (ΔZ) were calculated for both weight and height to determine changes in growth velocity. The mean Z scores for weight and height were markedly attenuated in CF children as compared with healthy children (−1.95 ± 0.23 and −2.8 ± 0.27, respectively). The mean ± SE for maximum stimulated GH value, IGF-1 and IGFBP-3 were 9.2 ± 1.2 ng/dl, 67 ± 6 ng/ml, and 1.7 ± 0.22 mg/L, respectively. GH treatment improved weight and height Z scores (−0.11 ± 0.05 and −0.94 ± 0.18, p<0.01) significantly. The ΔZ scores for weight and height were significantly increased during first and second year of GH treatment (p<0.02). Also, the average values of IGF-1 and IGFBP-3 were significantly increased as compared to pretreatment values (186 ± 37 ng/ml and 3.0 ± 0.22 mg/L, p<0.01).Conclusions: GH treatment significantly improves weight and linear growth in young patients with CF. These data suggest that anabolic effects of GH may be beneficial for treatment of malnutrition in children with CF.

Marked gender differences in ambulatory morning growth hormone values in young adults

The influence of gender on serum concentrations of growth hormone (GH) and 12 other endocrine analytes was investigated in sera drawn from 291 healthy medical students in the ambulatory state in the morning, after fasting overnight. GH was measured with a sensitive noncompetitive fluoroimmunoassay. The median GH value was 80-fold higher in women 21-26 years old than in age-matched men (14.4 vs 0.18 mIU/L), compared with a female/male ratio of 2.2 for 17beta-estradiol and a male/female ratio of 14 for testosterone. Furthermore, the values for sex hormone-binding globulin, follicle-stimulating hormone, luteinizing hormone, prolactin, and insulin-like growth factor 1 (IGF-1) were higher, whereas the values for free thyroxine, triiodothyronine, thyroid-stimulating hormone, and parathyroid hormone were lower in the women. The median GH value was 68-fold higher in women 27-43 years old than in age-matched men (10.9 vs 0.16 mIU/L). Women taking contraceptives with ethinyl estradiol and desogestrel or levonorgestrel had higher GH values, and the desogestrel group had lower IGF-1 values than women not taking contraceptives. The median GH values in these groups were 125- and 117-fold higher, respectively, than in men 21-26 years old. The results suggest that routine morning activity produces a marked GH response in >90% of young women but in very few age-matched men. The effect on GH was even more pronounced in women taking oral contraceptives, suggesting that the intake of ethinyl estradiol contributes to higher GH concentrations in these women.

The effects of short-term resistance training on endocrine function in men and women.

This investigation examined hormonal adaptations to acute resistance exercise and determined whether training adaptations are observed within an 8-week period in untrained men and women. The protocol consisted of a 1-week pre-conditioning orientation phase followed by 8 weeks of heavy resistance training. Three lower-limb exercises for the quadriceps femoris muscle group (squat, leg press, knee extension) were performed twice a week (Monday and Friday) with every other Wednesday used for maximal dynamic 1 RM strength testing. Blood samples were obtained pre-exercise (Pre-Ex), immediately post-exercise (IP), and 5 min post-exercise (5-P) during the first week of training (T-1), after 6 weeks (T-2) and 8 weeks (T-3) of training to determine blood concentrations of whole-blood lactate (LAC), serum total testosterone (TT), sex-hormone binding globulin (SHBG), cortisol (CORT) and growth hormone (GH). Serum TT concentrations were significantly (P < or = 0.05) higher for men at all time points measured. Men did not demonstrate an increase due to exercise until T-2. An increase in pre-exercise concentrations of TT were observed both for men and women at T-2 and T-3. No differences were observed for CORT between men and women; increases in CORT above pre-exercise values were observed for men at all training phases and at T-2 and T-3 for women. A reduction in CORT concentrations at rest was observed both in men and women at T-3. Women demonstrated higher pre-exercise GH values than men at all training phases; no changes with training were observed for GH concentrations. Exercise-induced increases in GH above pre-exercise values were observed at all phases of training. Women demonstrated higher serum concentrations of SHBG at all time points. No exercise-induced increases were observed in men over the training period but women increased SHBG with exercise at T-3. SHBG concentrations in women were also significantly higher at T-2 and T-3 when compared to T-1 values. Increases in LAC concentrations due to exercise were observed both for men and women for all training phases but no significant differences were observed with training. These data illustrate that untrained individuals may exhibit early-phase endocrine adaptations during a resistance training program. These hormonal adaptations may influence and help to mediate other adaptations in the nervous system and muscle fibers, which have been shown to be very responsive in the early phase of strength adaptations with resistance training.

Evaluation of growth hormone assays using ratio plots

To permit comparison between growth hormone (GH) results obtained using the Pharmacia polyclonal assay and the Delfia monoclonal assay, we used both methods to measure GH concentrations in peak GH responses to the pyridostigmine-growth-hormone-releasing-hormone (PD-GHRH) test and in unstimulated samples from 40 healthy adults and 31 patients with suspected GH deficiency. Ratio plots were used for the comparison, and acceptability criteria were based on inherent analytical imprecision and on analytical quality specifications. The mean ratio (r; Pharmacia/Delfia) for the peak GH responses in 40 healthy adults was calculated to be 1.59, and the 95% prediction interval for ratios fulfilling the imprecision criterion was applied. For GH values >1 mIU/L, the peak and unstimulated GH ratios in healthy adults and patients were within the 95% prediction interval, and fulfilled the biological criterion as well. Therefore, the conversion factor of 1.59 is applicable for the evaluation of GH-stimulation tests.

Excessive dietary protein and suboptimal caloric intake have a negative effect on the growth of children with chronic renal disease before and during growth hormone therapy

Although diet and nutrition are an integral part of the management of individuals with chronic renal failure (CRF), little has been written on the effect of nutrition on the growth response to growth hormone (GH) in CRF. We studied the GH axis and nutritional status of 31 prepubertal children aged 8.7 ± 0.5 years with a height standard deviation score (SDS) of −3.2 ± 0.2 (mean ± SEM) with CRF. Sixteen CRF patients on hemodialysis and 15 on peritoneal dialysis were studied. Forty-four age-matched normal short children without GH deficiency served as controls. Spontaneous 12-hour GH and stimulated GH values were significantly higher and GH binding protein (GHBP) was significantly lower in the CRF patients than in the normal short children. Both before the initiation of GH therapy and after the first year of treatment, the growth velocity (SDS) was inversely correlated with dietary protein intake and positively correlated with caloric intake. GH was administered at a dosage of 28 and 21 IU/m 2/wk to the CRF group and the normal short children, respectively, divided into seven daily doses. The growth response of the normal short children was significantly greater than that of the CRF patients. GH therapy induced a smaller increment in GHBP and IGF-I in the CRF patients versus the normal short children (8.8 ± 2.2 and 10.2 ± 2.7 v 24.8 ± 1.3 and 27.6 ± 2.5 nmol/L, respectively, P < .01). The 1-year growth velocity of the CRF children was most closely correlated with dietary protein and caloric intake. The nutritional status of CRF patients is concluded to be a major factor in growth both before and during GH therapy.

Post-traumatic hormonal disturbances: prolactin as a link between head injury and enhanced osteogenesis.

Traumatic brain injury (TBI) combined with fractures of long bones or large joints is often associated with enhanced osteogenesis (early fracture healing accompanied by hypertrophic callus formation and/or heterotopic ossifications). Humoral factors that cause enhanced osteogenesis in patients with TBI are not yet identified. The aim of this study was to reveal if post-traumatic change(s) of hormone levels in patients with TBI and bone fractures could be associated with the phenomenon of enhanced osteogenesis. The blood values of adrenocorticotropic hormone (ACTH), cortisol, growth hormone (GH), parathyroid hormone (PTH) and prolactin (PRL) were studied weekly over a period of three months after injury in patients with bone fractures only, those with TBI only or combined bone fractures and TBI (patients exerting enhanced osteogenesis). Stress-hormones, ACTH and cortisol, or the hormones related to the bone growth (GH and PTH) did not show any particular post-traumatic changes in the blood of patients with combined injury that could be associated with the enhanced osteogenesis. On the other hand, patients with combined bone fractures and TBI accompanied by enhanced osteogenesis had significantly elevated PRL levels in blood during the 5th week of the post-traumatic period. Thus, the maximal PRL values were measured at the time when in this group of patients fractures were in consolidation and hypertrophic callus or heterotopic ossifications were developing (as verified by x-ray imaging). Hence, PRL does not only influence physiology of the bone metabolism but also seems to be one of the humoral factors involved in the phenomenon of enhanced osteogenesis in patients with TBI.

The altered plasma amino acid pattern is responsible for the paradoxical growth hormone response to the oral glucose tolerance test in liver cirrhosis.

An increased basal growth hormone (GH) secretion and a parodoxical GH response to the oral glucose tolerance test (OGTT) have been reported in patients with liver cirrhosis. It has been suggested that the ratio between branched-chain amino acids (BCAAs) and aromatic amino acids (AAAs) (BCAA/ AAA ratio) may determine in part the brain concentration of the AAAs, since the BCAAs compete with the AAAs for entry across the blood-brain barrier, leading to the accumulation of false neurotransmitters such as octopamine and phenylethanolamine, which are able to stimulate GH secretion (via alpha 2-adrenergic stimulation). In this study we investigated the role of amino acids, particularly the BCAA/AAA ratio, in the paradoxical response of GH to the OGTT in patients with liver cirrhosis. Twelve non-diabetic patients with biopsy-proven cirrhosis of the liver underwent an OGTT. Three of the five patients with a paradoxical response of GH to the OGTT underwent a second oral glucose administration associated with an infusion of BCAA solution from -30 min until 180 min. During the OGTT, glucose and insulin levels increased from 4.8 +/- 0.2 to 9.6 +/- 0.7 mmol/l (P < 0.001) and from 18.8 +/- 2.6 to 104.4 +/- 13.8 mU/l (P < 0.005), respectively. GH levels increased from 8.6 +/- 2.6 to 22.4 +/- 10.8 mU/l although not significantly. Five patients had a paradoxical GH response to the OGTT. A negative correlation between serum GH values and BCAA/AAA ratio in the plasma at every time point of the OGTT was found. After co-administration of glucose and BCAA in three patients the BCAA/AAAs ratio increased, abolishing the paradoxical GH secretion. Our data suggest that in liver cirrhosis the altered BCAA/AAA ratio may influence the altered basal GH secretion and the paradoxical GH response to the OGTT, probably by an increase of adrenergic mediators in the brain. Moreover, the increase of BCAA/AAA ratio seems to be able to abolish the GH paradoxical response to the OGTT.

Registration system for growth hormone (GH) treatment with standardized immunoreactive GH values in Japan.

The Foundation for Growth Science has been controlling the use of GH by its registration system, which includes a scoring system for the eligibility for GH treatment according to the diagnostic criteria for GH deficiency (GHD) established by the Study Group for Hypothalamo-pituitary Disorder of the Ministry of Health and Welfare. Until 1995, 28,876 patients with GHD (19,432 boys and 9,444 girls) had been registered as eligible for GH treatment. The number of patients registered in a year increased gradually till 1990 due to the unlimited hGH supply by recombinant techniques and the change in the criteria for GH treatment and the number registered became stable after 1990. The frequency of GH-treated patients is calculated to be 55.2/100,000 persons (72.2/100,000 in boys and 37.1/100,000 in girls) in patients born between 1960 and 1990. The highest frequency was 148.4/100,000 persons (191.7/ 100,000 boys and 103.7/100,000 girls) in 1981, when 2,278 patients (1,508 boys and 770 girls) were born. Eligibility for GH treatment is assessed according to the scoring system which is basically dependent on peak GH values in provocation tests so that standardization of GH values measured with the various commercial GH kits is required to avoid inequality of patients' access to the treatment. In samples obtained by GRF test in 10 normal volunteers, hGH was measured with seven human GH (hGH) kits at a laboratory center. Since the RIA value has been used historically for the diagnosis of GHD, the mean of two RIA measurements was selected as the basis for the standardization procedure and the linear regression formula was used for each hGH kit. After the freely available supply of hGH obtained by recombinant DNA techniques, the role of the Foundation for Growth Science has changed to avoid hGH abuse. Even with this regulation, the frequency of registered patients may indicate a tendency to GH overuse.

Prognostic value of generation of growth hormone-stimulated insulin-like growth factor-I (IGF-I) and its binding protein-3 in patients with compensated and decompensated liver cirrhosis.

Our aim was to study the prognostic value of growth hormone (GH) -stimulated insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 (IGFBP-3) generation in patients with compensated [group 1 (N = 8) with a Child-Pugh (CP) score of 5-8] and decompensated postnecrotic liver cirrhosis [group 2 (N = 7) with a CP score of 9-12]. Serum levels of IGF-I, GH-binding protein (GHBP), and IGFBP-3 were measured before and 24 hr after a single subcutaneous injection of recombinant human GH (rhGH, 0.14 units/kg). Patients (mean age 56 years) were followed prospectively for three years. Six patients (40%) died during the follow-up period, of whom half had a CP score <9. Mean serum IGF-I levels 24 hr after rhGH injection (group 1 vs group 2, 17.4 +/- 6.8 vs 7.4 +/- 0.7 nmol/liter) predicted survival with 93% accuracy. Levels <10 nmol/liter portended a poor prognosis, with 15% survival at one year, whereas levels >10 nmol/liter had a 100% survival rate at one and two years, respectively. Baseline IGF-I (9.98 +/- 2.0 vs 6.38 +/- 0.8 nmol/liter), GHBP (9.2 +/- 3 vs 5.7 +/- 0.8%/50 microl), and IGFBP-3 serum levels at baseline (1.7 +/- 0.3 vs 0.86 +/- 0.2 mg/liter) and at 24 hr (2.04 +/- 0.38 vs 0.99 +/- 0.3 mg/liter) did not add to the predictive value of stimulated IGF-I levels at 24 hr and were less accurate in predicting the outcome in comparison to CP score (80%). We conclude that stimulated IGF-1 <10 nmol/liter may be a true predictor of a negative prognosis in patients with liver cirrhosis.

Plasma insulin and growth hormone during antarctic residence.

Circulatory levels of insulin and growth hormone (GH) were estimated in nine tropical euglycemic men in New Delhi and during the first week of every month of stay in Dakshin Gangotri, Antarctica. Prolonged residency in Antarctica did not alter GH levels because mean GH values during Austral summer and Austral winter were not significantly different from the New Delhi values. Compared with GH, the insulin levels during March, April, and June were found to be significantly lower than the New Delhi values. In Antarctica, the insulin levels in March, April, May, June, July, and August were also found to be significantly lower than the December values. This decline in insulin in Antarctica might be important in increasing substrate availability for heat production by facilitating lipolysis and hepatic glucose output.

Further studies on carry-over effects of dietary crude protein and triiodothyronine (T3) in broiler chickens.

Indian River male broiler chickens growing from 7 to 28 d of age were fed on diets containing either 120 or 210 g crude protein and 0 or 1 mg triiodothyronine (T3)/kg diet to study in vitro lipogenesis (IVL). In addition, a carry-over period (180 g crude protein/kg diet from 28 to 40 d of age) was used to test the persistence of prior treatment effects. The higher protein level increased, but T3 decreased (P < 0.01) growth and feed consumption at 28 d of age. The lower protein level increased (P < 0.05) and T3 decreased IVL in 28-d-old chickens. These effects were only sustained for 6 d following the switch to a common diet at 28 d. IVL at 40 d of age was not affected by either crude protein or T3 fed during the 7-28 d period. The higher protein level increased plasma insulin-like growth factor-1 during the period from 7 to 28 d; however, this effect lasted for only 6 d following the switch to a common diet. Plasma growth hormone (GH) at 28 d of age was inversely related to dietary protein level. Changing to a common level of crude protein did not change plasma GH values at 12 d, indicating that the nutritional state of the young chicken may affect GH at a later period of life. Metabolic changes noted in this study were rapid and maintained for a short period of time following the feeding of a common diet.

Uses and abuses of growth hormone

Summary At present in the UK, growth hormone is licensed for the treatment of short stature caused by impaired growth hormone secretion, Turner's syndrome, renal failure and for hormone replacement in adults known to be growth hormone-deficient. It is clear that there are significant benefits of treatment on the final heights of children with growth hormone deficiency. In contrast, the benefits of therapy on the final height of children with Turner's syndrome may not be as great as were originally anticipated. The optimum method of increasing final height in both Turner's syndrome and renal failure is yet to be established and, if such children are treated long-term, the value of continued growth hormone in individual cases requires constant realistic re-evaluation. Although growth hormone has been shown to accelerate the short-term growth of children with a variety of other causes of short stature, the widespread and idiosyncratic use of growth hormone cannot be justified in these other groups until the benefits of therapy on final height have been demonstrated by carefully conducted research studies involving comparisons with suitably randomized, untreated control groups.

Lack of effect of methylphenidate on serum growth hormone (GH), GH-binding protein, and insulin-like growth factor I.

The aim of this study was to assess the growth hormone (GH) axis in methylphenidate (MPH)-treated and untreated boys with attention-deficit and hyperactivity disorder (ADHD), by evaluating serum GH, GH-binding protein (GHBP) activity, and insulin-like growth factor I (IGF-I) levels as compared to age-matched normal controls. Blood samples were taken from 42 boys (aged 6-16 years) diagnosed as having ADHD according to DSM-III-R criteria and confirmed by using the Schedule for Affective Disorder and Schizophrenia for school-age children (K[Kiddle]-SADS). A total of 21 patients were treated with MPH (5-20 mg/day; 0.15-0.77 mg/kg/day), on a drug holiday protocol, for 1-36 months, and 21 were drug naive. A total of 46 age-matched normal boys at height and weight within normal range served as controls. No significant differences were detected between the MPH-treated ADHD children, the untreated ADHD children, and the control children on fasting serum GH levels, GHBP activity, or IGF-I levels. Active treatment with MPH, in ADHD children on a drug holiday protocol, does not cause changes in GH axis as manifested by normal values of GH, GHBP, and IGF-I.

Growth hormone (GH) assays: influence of standard preparations, GH isoforms, assay characteristics, and GH-binding protein

The impact of the adoption of the new biosynthetic growth hormone (GH) WHO International Reference Preparation (IRP 88/624), and the recommendation to report results in microgram/L instead of mU/L, is described. Conversion factors were determined by comparing both the linear and nonlinear relations of the GH values. The Pharmacia polyclonal IRMA (p-IRMA) and the DELFIA monoclonal time-resolved immunofluorometric assay (trIFMA) with kit calibrators calibrated either against the pituitary-derived WHO IRP 80/505 or the new 88/624 were evaluated. Conversion factors of 4.17 mU/L = 1 microgram/L for the p-IRMA and 4.31 mU/L = 1 microgram/L for the trIFMA were necessary. Different cross-reactivity patterns for the deaminated and dimer 22-kDa, 20-kDa, and 17-kDa GH isoforms were found. Expected GH recovery was similar when the measured values were adjusted according to the results of the cross-reactivity study.