Changes in skeletal muscle and body composition after discontinuation of growth hormone treatment in growth hormone deficient young adults

Association Between the Growth Hormone/Insulin-Like Growth Factor-1 Axis and Muscle Density in Children and Adolescents of Short Stature

OBJECTIVE

To evaluate the association between the growth hormone (GH)/insulin-like growth factor-1 (IGF-1) axis and muscle density in children and adolescents of short stature.

METHODS

Participants were children and adolescents of short stature hospitalized in the Affiliated Hospital of Jining Medical University between January 2020 and June 2021. All participants had CT scan images available. We performed an analysis of the images to calculate the muscle density or skeletal muscle attenuation (SMA), skeletal muscle index (SMI), and fat mass index (FMI). Bioelectrical impedance analysis (BIA) was used to ensure that chest CT is a credible way of evaluating body composition.

RESULTS

A total of 297 subjects were included with the mean age of 10.00 ± 3.42 years, mean height standard deviation score (SDS) of -2.51 ± 0.53, and mean IGF-1 SDS of -0.60 ± 1.07. The areas of muscle and fat tissues at the fourth thoracic vertebra level in the CT images showed strong correlation with the total weights of the participants (R²  = 0.884 and 0.897, respectively). The peak of GH was negatively associated with FMI (r = - 0.323, P <.01) and IGF-1 SDS was positively associated with SMI (r = 0.303, P <.01). Both the peak GH and IGF-1 SDS were positively associated with SMA (r = 0.244, P <.01 and r = 0.165, P <.05, respectively). Multiple stepwise linear regression analysis demonstrated that the GH peak was the predictor of FMI (β = - 0.210, P < .01), the IGF-1 SDS was the predictor of SMI (β = 0.224, P < .01), and both the peak GH and IGF-1 SDS were predictors of SMA (β = 0.180, P < .01 and β = 0.222, P < .01).

CONCLUSIONS

A chest CT scan is a credible method of evaluating body composition in children and adolescents of short stature. In these patients, peak GH and IGF-1 SDS are independent predictors of muscle density and the GF/IGF-1 axis may regulate body composition through complex mechanisms.

Possible effects of an early diagnosis and treatment in patients with growth hormone deficiency: the state of art

Growth hormone deficiency (GHD) is a relatively uncommon and heterogeneous endocrine disorder presenting in childhood with short stature. However, during the neonatal period, the metabolic effects of GHD may to require prompt replacement therapy to avoid possible life-threatening complications. An increasing amount of data suggests the importance of an early diagnosis and treatment of GHD because of its auxological, metabolic, and neurodevelopmental features with respect to the patients diagnosed and treated later in life.

The available results show favourable auxological outcomes for patients with GHD diagnosed and treated with r-hGH early in life compared with those from patients with GHD who do not receive this early diagnosis and treatment. Because delayed referral for GHD diagnosis and treatment is still frequent, these results highlight the need for more attention in the diagnosis and treatment of GHD.

Despite these very encouraging data regarding metabolic and neurodevelopmental features, further studies are needed to better characterize these findings. Overall, the importance of early diagnosis and treatment of GHD needs to be addressed.

Muscle and skeletal health in children and adolescents with GH deficiency

In addition to promoting linear growth, GH plays a key role in the regulation of bone and muscle development and metabolism. Although GH deficiency is frequently listed among the causes of secondary osteoporosis in children, its impact on bone and muscle health and on fracture risk is still not completely established. Current data suggest that childhood-onset GH deficiency can affect bone and muscle mass and strength, with GH replacement therapy exerting beneficial effects. Moreover, GH withdrawal at final height can result in reduced peak bone and muscle mass, potentially leading to increased fracture risk in adulthood. Thus, the muscle-bone unit in GH deficient subjects should be monitored during childhood and adolescence in order to prevent osteoporosis and increased fracture risk and GH replacement should be tailored to ensure an optimal bone and muscle health.

Growth hormone deficiency during young adulthood and the benefits of growth hormone replacement

Until quite recently, the management of children with growth hormone deficiency (GHD) had focussed on the use of recombinant human GH (rhGH) therapy to normalise final adult height. However, research over the past two decades that has demonstrated deficits in bone health and cardiac function, as well as impaired quality of life in adults with childhood-onset GHD (CO-GHD), has questioned this practice. Some of these studies suggested that there may be short-term benefits of rhGH in certain group of adolescents with GHD during transition, although the impact of GHD and replacement during the transition period has not been adequately investigated and its long-term benefits remain unclear. GH therapy remains expensive and well-designed long-term studies are needed to determine the cost effectiveness and clinical benefit of ongoing rhGH during transition and further into adulthood. In the absence of compelling data to justify widespread continuation of rhGH into adult life, there are several questions related to its use that remain unanswered. This paper reviews the effects of growth hormone deficiency on bone health, cardiovascular function, metabolic profile and quality of life during transition and young adulthood.

United States multicenter study of factors predicting the persistence of GH deficiency during the transition period between childhood and adulthood

Background

Many patients with childhood-onset growth hormone (GH) deficiency do not fulfill diagnostic criteria for GH deficiency (GHD) after attainment of adult height and may not require long-term GH treatment. Patients with history of idiopathic GHD (IGHD) pose the greatest management dilemma, as data regarding factors predictive of persistent GHD in this group are lacking.

Objectives

The objective of this study was to assess potential predictors of persistent GHD in a US patient cohort during transition from childhood to adulthood, particularly in patients with history of IGHD.

Methods

We studied 73 US patients with history of childhood-onset GHD screened at 21 US pediatric endocrine centers for a randomized clinical trial of GH replacement after attainment of adult height. The cohort comprised 42 boys/men and 31 girls/women aged14–22 years, who had received ≥1 year of GH treatment and had completed linear growth. The main outcome measures were sensitivity, specificity, positive and negative predictive values (PPV, NPV) of clinical and hormonal factors for persistent GHD (defined a priori in this study as peak GH < 5 μg/L).

Results

For the cohort as a whole, the best predictors of persistent GHD (100% PPV) were history of organic hypothalamic-pituitary disorder or ≥2 additional pituitary hormone deficiencies (PHD). Best predictors of persistent GHD in patients with childhood history of IGHD were standard deviation scores (SDS) for serum insulin-like growth factor binding protein-3 (IGFBP-3) below -2.0, and for insulin-like growth factor-I (IGF-I) below -5.3 (measured ≥6 weeks after completion of GH treatment; PPV 100% for both), and age <4 years at original diagnosis (PPV 89%). IGF-I above -1.6 SDS had 100% NPV.

Conclusions

US patients with an organic cause of childhood-onset GHD or ≥2 additional PHDs may not require GH stimulation testing to reconfirm GHD after completion of childhood treatment. In contrast, patients with idiopathic childhood-onset GHD almost invariably require retesting, as GHD persists in only a minority (those who were very young at initial diagnosis and those who have subnormal IGFBP-3 or extremely low IGF-I after completion of childhood treatment). Subnormal posttreatment IGF-I (<-2.0 SDS) lacked predictive power for persistent GHD, whereas IGF-I > -1.6 SDS was 100% predictive of GH sufficiency.

Hormone replacement therapy and physical function in healthy older men. Time to talk hormones?

Improving physical function and mobility in a continuously expanding elderly population emerges as a high priority of medicine today. Muscle mass, strength/power, and maximal exercise capacity are major determinants of physical function, and all decline with aging. This contributes to the incidence of frailty and disability observed in older men. Furthermore, it facilitates the accumulation of body fat and development of insulin resistance. Muscle adaptation to exercise is strongly influenced by anabolic endocrine hormones and local load-sensitive autocrine/paracrine growth factors. GH, IGF-I, and testosterone (T) are directly involved in muscle adaptation to exercise because they promote muscle protein synthesis, whereas T and locally expressed IGF-I have been reported to activate muscle stem cells. Although exercise programs improve physical function, in the long-term most older men fail to comply. The GH/IGF-I axis and T levels decline markedly with aging, whereas accumulating evidence supports their indispensable role in maintaining physical function integrity. Several studies have reported that the administration of T improves lean body mass and maximal voluntary strength in healthy older men. On the other hand, most studies have shown that administration of GH alone failed to improve muscle strength despite amelioration of the detrimental somatic changes of aging. Both GH and T are anabolic agents that promote muscle protein synthesis and hypertrophy but work through separate mechanisms, and the combined administration of GH and T, albeit in only a few studies, has resulted in greater efficacy than either hormone alone. Although it is clear that this combined approach is effective, this review concludes that further studies are needed to assess the long-term efficacy and safety of combined hormone replacement therapy in older men before the medical rationale of prescribing hormone replacement therapy for combating the sarcopenia of aging can be established.

Growth hormone deficiency in the transition period: body composition and gonad function

Recombinant GH therapy is normally administered to GH-deficient children in order to achieve a satisfactory height - the main target during childhood and adolescence. However, the role of GH does not end once final height has been reached, but continues during the so-called transition period. In this phase of life, the body undergoes several changes, both physical and psychological, that culminate in adulthood. During this period, GH has a part in numerous metabolic functions. These include the lipid profile, where it increases HDL and reduces LDL, with the global effect of cardiovascular protection. It also has important effects on body composition (improved muscle strength and lean body mass and reduced body fat), the achievement of proper peak bone density, and gonad maturation. Retesting during the transition period, involving measurement of IGF-I plus a provocative test (insulin tolerance test or GHRH + arginine test), is thus necessary to establish any persistent GH deficiency requiring additional replacement therapy. The close cooperation of the medical professionals involved in the patient's transition from a pediatric to an adult endocrinologist is essential. The aim of this review is to point out the main aspects of GH treatment on body composition, metabolic and gonad functions in the transition period.

The effect of growth hormone (GH) replacement on muscle strength in patients with GH-deficiency: a meta-analysis

CONTEXT/OBJECTIVES

GH replacement increases muscle mass and reduces body fat in growth hormone deficiency (GHD) adults. A recent meta-analysis has demonstrated that this improvement in body composition is associated with improved exercise performance. The current meta-analysis was carried out to determine whether high-quality evidence exists to support a beneficial effect of GH replacement on strength.

DESIGN/METHODS

An extensive Medline search/literature review identified eight studies with utilizable, robust data, involving 231 patients in nine cohorts. Previously unpublished data were sought from authors and obtained in two cases. All studies included were randomized, double-blind, placebo-controlled, of parallel or cross-over design and of an average 6.7 months duration. Information was retrieved in uniform format, with data pertaining to patient numbers, study-design, GH-dose, mean age, IGF-I levels and muscle strength measurements (isometric or isokinetic quadriceps strength) recorded. Data were analysed using a fixed-effects model, utilizing continuous data measured on different scales. A summary effect measure (d(s)) was derived for individual strength variables, whereas an overall summary effect was derived from the sum of all studies incorporating different variables; 95% CIs were calculated from the weighted variances of individual study effects.

RESULTS

Analysis revealed no significant improvement, neither when all studies were combined (d(s) = +0.01 +/- 0.26) nor when measured individually (isometric quadriceps strength, d(s) = +0.02 +/- 0.32 and isokinetic quadriceps strength, d(s) = 0.00 +/- 0.45).

CONCLUSIONS

Evidence from short-term controlled studies fails to support a benefit on muscle strength of GH replacement in GHD patients, which is likely to occur over a longer time-course, as seen in open-label studies.

Modulation of GH/IGF-1 axis: potential strategies to counteract sarcopenia in older adults

Aging is associated with progressive decline of skeletal muscle mass and function. This condition, termed sarcopenia, is associated with several adverse outcomes, including loss of autonomy and mortality. Due to the high prevalence of sarcopenia, a deeper understanding of its pathophysiology and possible remedies represents a high public health priority. Evidence suggests the existence of a relationship between declining growth hormone (GH) and insulin-like growth factor-1 (IGF-1) levels and age-related changes in body composition and physical function. Therefore, the age-dependent decline of GH and IGF-1 serum levels may promote frailty by contributing to the loss of muscle mass and strength. Preclinical studies showed that infusion of angiotensin II produced a marked reduction in body weight, accompanied by decreased serum and muscle levels of IGF-1. Conversely, overexpression of muscle-specific isoform of IGF-1 mitigates angiotensin II-induced muscle loss. Moreover, IGF-1 serum levels have been shown to increase following angiotensin converting enzyme inhibitors (ACEIs) treatment. Here we will review the most recent evidence regarding age-related changes of the GH/IGF-1 axis and its modulation by several interventions, including ACEIs which might represent a potential novel strategy to delay the onset and impede the progression of sarcopenia.

[Management of the growth hormone (GH)-treated patients with diagnosis of GH deficiency (DGH) during transition from childhood to adulthood]

Growth hormone (GH) has many beneficial effects in patients with childhood-onset GH deficiency (GHD) in addition to its promotion of linear growth. The discontinuation of GH treatment in GHD patients, during the transition from childhood to adulthood, induces significant unfavorable changes in body composition, skeletal integrity, exercise capacity, and an adverse cardiovascular risk profile. These changes are reversed after the resumption of GH treatment. As the benefits of continuing GH therapy into adulthood has been well established, it is possible that GH replacement therapy will not be stopped once growth has been completed, but it will continue into adult life. Considering that a high proportion of patients with diagnosis of DGH in childhood are no longer GHD in adolescence, the GH status must be retested when growth is completed. Other factors such as clinical history, GH response in childhood, hipotalamic-pituitary MRI and IGF-1 concentration must be considered. Reconfirmation of GHD diagnosis through stimulation testing is usually required, unless there is a proven genetic or structural lesion persistent from childhood.

Are survivors of acute lymphoblastic leukemia (ALL) at increased risk of cardiovascular disease?

Through a variety of different mechanisms, it appears that survivors of childhood acute lymphoblastic leukemia have an increased prevalence of several cardiovascular risk factors and thus are at increased risk for developing cardiovascular disease. The aim of this paper is to describe the current understanding of particular risk factors, including obesity, physical inactivity, dyslipidemia, insulin resistance, and metabolic syndrome, that may contribute to cardiovascular disease in survivors of childhood ALL. The potential roles of different cancer therapies in the development of these risk factors are discussed. In addition, two other late effects that may affect cardiovascular health are discussed: late-onset anthracycline-induced left ventricular dysfunction and methotrexate-mediated elevations of homocysteine during therapy with the potential for endothelial dysfunction. Lastly, areas needing further investigation to elucidate these risks are highlighted.

Management of growth hormone deficiency in adults

Growth hormone (GH) deficiency in adults is a recognised clinical entity. There is still, however, an ongoing debate of the clinical need and the importance of replacing GH in adults with severe GH deficiency. This review will focus on the overall management of adults with GH deficiency and highlight published data on dose management and treatment goals for various age groups. The efficacy data on quality of life and well-being is discussed and available and growing experience on long-term effects of GH replacement in adults and safety in terms of diabetes mellitus, pituitary tumour recurrence/regrowth and malignancy risk will be reviewed.

Physical Inactivity in Adult Survivors of Childhood Acute Lymphoblastic Leukemia: A Report from the Childhood Cancer Survivor Study

PURPOSE

To determine if adult survivors of childhood acute lymphoblastic leukemia (ALL) are less active (and more inactive) than the general population and to identify modifying factors.

PATIENTS AND METHODS

Physical activity was assessed by self-report in 2,648 adult survivors of the Childhood Cancer Survivor Study. Participants in the Behavioral Risk Factor Surveillance System (BRFSS) survey administered through the Centers for Disease Control and Prevention (CDC) were used as a comparison group.

RESULTS

Survivors had a mean age of 28.7 years (range, 18.0-44.0 years) and were a mean of 23.1 years from their cancer diagnosis (range, 16.0-33.8 years). In multivariate models, ALL survivors were more likely to not meet CDC recommendations for physical activity [odds ratio (OR), 1.44; 95% confidence interval (95% CI), 1.32-1.57] and more likely to be inactive (OR, 1.74; 95% CI, 1.56-1.94) in comparison with the BRFSS general population. Survivors treated with >20-Gy cranial radiotherapy were at particular risk. Compared with BRFSS participants and adjusted for age, race, and ethnicity, survivors were more likely to not meet CDC recommendations (females: OR, 2.07, 95% CI, 1.67-2.56; males: OR, 1.43, 95% CI, 1.16-1.76) and more likely to be inactive (females: OR, 1.86; 95% CI, 1.50-2.31; males: OR, 1.84; 95% CI, 1.45-2.32).

CONCLUSIONS

Long-term survivors of childhood ALL are less likely to meet physical activity recommendations and more likely to report no leisure-time physical activity in the past month. This level of inactivity likely further increases their risk of cardiovascular disease, osteoporosis, and all-cause mortality.

Growth hormone and the transition from puberty into adulthood

With modern growth hormone (GH) replacement algorithms, children with a diagnosis of growth hormone deficiency achieve at the end of pediatric GH treatment an adult height that is on the average in the normal range. Recent experience with GH replacement in young adults with childhood-onset growth hormone deficiency, however, has shown that these patients present with variable degrees of somatic immaturity. As childhood GH treatment is discontinued when final height is attained, attention moves to the phase of somatic development that follows the end of longitudinal growth, called ''transition'', which had been excluded previously from consideration for either pediatric or adult GH replacement. This article reviews the changes taking place during this phase of development and their relevance for the attainment of adult body maturation. The critical role of GH in this process is described.

Indications and strategies for continuing GH treatment during transition from late adolescence to early adulthood in patients with GH deficiency: the impact on bone mass

GH plays an important role in longitudinal bone growth and maturation during childhood and adolescence. However, GH has important metabolic functions other than bone growth, which become more apparent during young adulthood, when growth has been completed. Indeed, GH deficiency (GHD) in adult life is a recognized clinical syndrome which includes symptoms such as increased central adiposity, decreased lean body mass, reduced bone mineral density (BMD), increased atherogenic risk, cerebrovascular and cardiac morbidity and mortality, and reduced quality of life. As approximately one quarter of the children with GHD should continue GH administration in adulthood, it is important to reconfirm GHD at the end of growth in order to select patients with severe GHD who need to resume GH therapy with an appropriate age-related dosage. Some evidence indicates that most peak bone mass (PBM) is achieved by the end of adolescence but small increases in BMD continue during the period of transition from late adolescence to young adulthood. Some young adults with GHD show a persistent increase of lumbar BMD after the completion of growth even after discontinuation of treatment suggesting a spontaneous progression towards lumbar PBM or a continuing effect of the treatment. The data indicates that adolescents with GHD who do not reach lumbar PBM at the time of discontinuation of GH treatment can achieve a BMD lower than their genetic potential if they are not treated during the transition to young adulthood.

Stepping into Adulthood: The Transition Period

The period of growth from late puberty to full adult maturation, termed the transition period, is important for tissue maturation. Peak bone mass, muscle mass and strength are usually attained in this period. However, it is common clinical practice in children with growth hormone deficiency (GHD) to discontinue growth hormone (GH) treatment in adolescence after attainment of final height. Therefore, patients with childhood-onset GHD that continues into adulthood and who do not receive treatment as adults may experience more severe consequences than patients who acquire GHD as an adult. Recent studies indicate that bone and muscle maturation are attenuated if GH treatment is discontinued at final height. Furthermore, these patients will also develop cardiovascular risk factors that are normally associated with GHD in adults. Much debate surrounds when retesting for GHD should be carried out and when GH treatment should be restarted in adolescents; many of these patients will not have severe GHD according to the criteria set for adults. The transition period is an appropriate time to modify GH doses. Finally, registries exist that have recorded clinical treatment experiences for children and adults. Tools that collect and analyse data provide an important opportunity to investigate issues related to transition.

Adolescents with partial growth hormone (GH) deficiency develop alterations of body composition after GH discontinuation and require follow-up

It is now a consensus to resume GH treatment in adolescents with severe GH deficiency (GHD) at retesting to prevent the occurrence of adult GHD syndrome. However, we do not have any data on the follow-up of adolescents with nonsevere GHD at completion of treatment. This report presents preliminary data from a 1-yr prospective study that includes the first 91 patients retested. Anthropometric data, IGF-I and IGF binding protein-3 levels, glycemia and insulinemia, lipid profile, and body composition using dual x-ray absorptiometry and abdominal computed tomography scan were recorded at completion of GH treatment and 1 yr later. Body composition was significantly different at both evaluations, with increased total body fat and decreased lean body mass in the partial GHD group vs. the normal group. Moreover, these alterations worsened after 1 yr without GH in the partial GHD group, whereas there were no modifications in the normal group. We did not find any metabolic alterations such as elevated triglyceride, total cholesterol, or insulin levels. Adolescents with reconfirmed partial GHD exhibit alterations in body composition after 1 yr without GH, whereas those retested normal do not. These changes are similar to those described in severe GHD, although less marked, and justify a precise follow-up.

Effects of lowering circulating free fatty acid levels on protein metabolism in adult growth hormone deficient patients

Our study was conducted to define the roles of lowering circulating free fatty acids (FFA) and of growth hormone (GH) replacement on protein metabolism in GH deficient patients. To isolate the specific effects of FFA and GH we studied seven adult subjects with GH deficiency four times: (A) with administration of GH and Acipimox (an inhibitor of lipolysis), (B) with GH, without Acipimox, (C) without GH, with Acipimox and (D) without either. Each study included a 3 h basal period and a 3 h euglycemic clamp. Amino acid metabolism was assessed by stable isotope dilution technique at the whole body level and across the forearm. Overall, we saw no intervention effect on protein metabolism, but when the two situations in which Acipimox was given were combined, Acipimox decreased basal plasma FFA concentrations by 75% and increased serum urea concentrations by 20%, whole body appearance rates (reflecting protein degradation) of phenylalanine (by 7%) and tyrosine (by 11%) and protein synthesis rates for phenylalanine (by 7%), whereas phenylalanine-to-tyrosine conversion was unaffected. Acipimox more than doubled net forearm phenylalanine release during the clamp and increased basal forearm phenylalanine disappearance (reflecting muscle protein synthesis). During the clamp whole body amino acid fluxes and phenylalanine-to-tyrosine conversion decreased together with a decrease in forearm protein breakdown. GH replacement did not affect any of these metabolic parameters. Although we failed to show any role for GH, the results show that lowering of FFA concentrations with Acipimox has pronounced effects on protein metabolism, including increased whole body and forearm protein breakdown, together with increased protein synthesis systemically and locally in the forearm. The increase in serum urea and a doubling of net forearm phenylalanine release after lowering of FFA strongly indicate that the overall effect is catabolic and supports a pivotal protein conserving role of lipids.

Body composition, IGF-I and IGFBP-3 concentrations as outcome measures in severely GH-deficient (GHD) patients after childhood GH treatment: a comparison with adult onset GHD patients

If GH therapy of children with GH deficiency (GHD) has been adequate, body composition should be comparable to that of patients who have undergone normal childhood development and become hypopituitary thereafter. To assess this, body composition was determined in 92 patients with childhood onset (CO) GHD, aged 18-30 yr, who had been treated to final height with GH for 8.98 +/- 4.30 yr and had stopped treatment 1.57 +/- 1.20 yr previously, but who remained GHD (assessed by a GH stimulation test and IGF-I values). These were compared with 35 age-matched GH-naïve hypopituitary patients with adult onset (AO) GHD. Lean body mass, fat mass, and total bone mineral content were assessed by dual energy x-ray absorptiometry and corrected for actual height. CO patients were shorter (CO height, -1.18 +/- 1.16 SD score; AO height, -0.38 +/- 1.12 SD score; P < 0.001) and had lower body mass index (CO, 23.19 +/- 5.76 kg/m(2); AO, 28.9 +/- 6.27 kg/m(2); P < 0.001) than the AO group. Although there were gender differences, within genders CO patients had lower lean body mass, fat mass, and bone mineral content (P < 0.001 in all cases) compared with AO patients. Standard deviation scores for IGF-I (CO female, -9.2 +/- 3.1; AO female, -5.2 +/- 2.6; CO male, -6.4 +/- 2.7; AO male, -3.5 +/- 2.3; P < 0.001 within each gender) and IGFBP-3 (CO female, -3.5 +/- 2.5; AO female, -1.7 +/- 1.5; CO male, -2.8 +/- 2.0; AO male, -1.1 +/- 1.6; P < 0.001 within each gender) were significantly lower in the CO group. These results suggest that patients with CO GHD who were treated to final height suffer a significant maturational deficit despite GH replacement during childhood.

GH is needed for the maturation of muscle mass and strength in adolescents

The postpubertal period and the early years of adulthood may be of importance for continuing tissue maturation of importance in adulthood and aging. An example of this is the peak bone mass. This study has evaluated the importance of GH for lean mass and muscle strength in adolescents and young adults. GH treatment was discontinued in 40 adolescents aged 16-21 yr with GH deficiency of childhood onset. Measurements of isometric and isokinetic knee-extensor and flexor strength, handgrip strength, lean body mass, fat-free mass, and total body nitrogen were performed annually for 2 yr. Two hundred fifty healthy adolescents were randomly selected for prospective measurements of lean mass and handgrip strength between the ages of 17 and 21 yr. In the adolescents with continuing GH deficiency, lean body mass decreased, compared with the patients defined as having sufficient endogenous GH. The isometric strength in knee flexors increased in the sufficient endogenous GH group and was unchanged in the GH deficiency group during the 2 yr off GH treatment (between group, P < 0.05). The mean and peak handgrip strength increased on average by 9-15% in the group with sufficient endogenous GH and was unchanged in those with GH deficiency (P < 0.05). Lean body mass and handgrip strength (both, P < 0.001) increased in both the healthy boys and girls who were followed for 4 yr with a more marked increase in the boys. The mean increase in handgrip between the age of 17 and 21 yr was 7-9%. The increased lean mass and improved muscle performance seen in healthy adolescents did not occur in adolescents with GH deficiency. These findings suggest that GH is of importance for the maturation of lean mass and muscle strength in adolescents and young adults.

Diagnosis and management of growth hormone deficiency in adults

In adults, GHD is a clinical syndrome that occurs in patients with pituitary or hypothalamic disease. It may be asymptomatic or present with relatively nonspecific constitutional symptoms. Most patients have abnormal body composition, consisting of increased fat mass and decreased lean mass. Life expectancy is significantly decreased in hypopituitary patients with GHD, with cardiovascular disease a common cause of death. Treatment with growth hormone reverses abnormalities in body composition and may reduce cardiovascular risk factors; however, the long-term treatment outcomes regarding mortality, the incidence of cardiovascular disease, bone fractures, tumor development, and recurrence are not known. Longer prospective clinical studies are needed. The major manufacturers of growth hormone have initiated postmarketing surveillance databases to monitor the safety of growth hormone treatment.

Optimizing gh therapy in adults and children

Until the advent of modern neuroradiological imaging techniques in 1989, a diagnosis of GH deficiency in adults carried little significance other than as a marker of hypothalamo-pituitary disease. The relatively recent recognition of a characteristic clinical syndrome associated with failure of spontaneous GH secretion and the potential reversal of many of its features with recombinant human GH has prompted a closer examination of the physiological role of GH after linear growth is complete. The safe clinical practice of GH replacement demands a method of judging overall GH status, but there is no biological marker in adults that is the equivalent of linear growth in a child by which to judge the efficacy of GH replacement. Assessment of optimal GH replacement is made difficult by the apparent diverse actions of GH in health, concern about the avoidance of iatrogenic acromegaly, and the growing realization that an individual's risk of developing certain cancers may, at least in part, be influenced by cumulative exposure to the chief mediator of GH action, IGF-I. As in all areas of clinical practice, strategies and protocols vary between centers, but most physicians experienced in the management of pituitary disease agree that GH is most appropriately begun at low doses, building up slowly to the final maintenance dose. This, in turn, is best determined by a combination of clinical response and measurement of serum IGF-I, avoiding supraphysiological levels of this GH-dependent peptide. Numerous studies have helped define the optimum management of GH replacement during childhood. The recent requirement to measure and monitor GH status in adult life has called into question the appropriateness of simplistic weight- and surface area-based dosing regimens for the management of GH deficiency in childhood, with reliance on linear growth as the sole marker of GH action. It is clear that the monitoring of parameters other than linear growth to help refine GH therapy should now be incorporated into childhood GH treatment protocols. Further research will be required to define the optimal management of the transition from pediatric to adult GH replacement; this transition will only be possible once the benefits of GH in mature adults are defined and accepted by pediatric and adult endocrinologists alike.

Growth hormone therapy in adults

The importance of growth hormone (GH) deficiency in adults became evident 10 to 15 years ago, when the first clinical studies on GH replacement therapy in adults were published. Since then, a number of studies have been reported showing that GH replacement therapy can improve this condition. Adult GH deficiency (GHD) is now recognized as a specific clinical syndrome and the first reports of long-term use of GH (up to 10 years) are now being published. The aim of this paper was to review the accumulated data on the various clinical aspects of adult GHD.

Estimation of body composition in muscular dystrophy by MRI and stereology

We have applied the Cavalieri method of modern design stereology with magnetic resonance imaging for estimating the volume of whole-body muscle and fat compartments in four patients with muscular dystrophy, a patient with myopathy, five controls, an anorexic subject, and a body builder. Detailed systematic series (ie, 50) of axial MR images (T1-weighted, TR/TE 400/10 msec) were obtained throughout the whole body of each subject. The results showed that 15, 20, and 35 axial sections through the body are sufficient to secure coefficients of error (CEs) on the estimates of total muscle and fat volume of around 10%, 5%, and 3% respectively in muscular dystrophy patients and controls. The mean normalized volumes of muscle in four muscular dystrophy patients were decreased by 27% (t-test: P < 0.05), and those of total fat were increased by 12% (t-test: P > 0.05) relative to controls. The Cavalieri method provides a direct, efficient, and mathematically unbiased approach for studying human body compartments and may have application in assessing treatment efficacy in patients with muscular dystrophy. J. Magn. Reson. Imaging 2000;12:467-475.

[Growth hormone deficiency. Treatment with growth hormone and body composition]

Increased fat mass, decreased lean mass, muscular mass and bone mineral density are characteristic of the body composition in GH deficiency, GH treatment reverses these abnormalities. Body composition was determined in 20 young adults with GHD diagnosed in childhood, whose GH treatment was stopped 1 year earlier. Reevaluation of GH secretion in these patients showed that 12 remained GH deficient (confirmed GHD) while eight recovered normal GH secretion (transient GHD). One year after stopping the GH treatment, patients with confirmed GHD showed an increased fat mass as compared with value at the end of the treatment; in addition a decreased bone mineral content was observed in the patients with low physical activity. There was no increased fat mass in transient GHD; however, these patients presented with low bone mineral content, as previously reported in adults with history of delayed growth and adolescence.

Continuation of growth hormone (GH) replacement in GH-deficient patients during transition from childhood to adulthood: a two-year placebo-controlled study

Previous studies have demonstrated beneficial effects of GH replacement, in adults with GH deficiency (GHD), on body composition, physical fitness, and quality of life. These studies, however, concern patients with adult-onset GHD or childhood-onset (CO) patients enrolled several years after withdrawal of initial therapy. So far, the effects of continuation of GH-administration in patients with CO-GHD have not been examined. We studied a group of nineteen young adults (13 males + 6 females; 16-26 yr old; mean age, 20.2 +/- 0.65 yr) with CO-GHD, in a randomized, parallel, double-blind, placebo-controlled trial for 1 yr, followed by an open phase with GH for 1 yr. All patients received GH therapy at the start of study, and trial medication (GH/placebo) was given in a similar dose. Patients randomized to continued GH treatment exhibited no significant changes in any parameters tested, but intra- and interindividual variations in insulin-like growth factor (IGF)-I levels could suggest compliance problems. Discontinuation of GH for 1 yr resulted in a decrease in serum IGF-I, from 422.0 +/- 56.8 to 147.8 +/- 33.4 microg/L, in the placebo group (P = 0.003). After discontinuation of GH for 1 yr, an increase in total body fat (TBF, kg), measured by dual-energy x-ray absorptiometry scan, was seen [placebo: 22.7 +/- 2.7 to 26.5 +/- 2.5 (P = 0.01); GH: 16.2 +/- 2.1 to 17.2 +/- 2.1 (not significant)]. Resumption of GH after placebo was followed by increments in serum IGF-I (microg/L) [from 147.8 +/- 33.4 to 452 +/- 76 (P = 0.001)] and IGF-binding protein 3, as well as in fasting glucose (mmol/L) [4.9 +/- 0.2 vs. 5.3 +/- 0.2 (P = 0.03)]. After resumption of GH lean body mass (kg) increased [52.4 +/- 4.9 vs. 60.7 +/- 5.6 (P = 0.006)]. Likewise, resumption of GH therapy increased thigh muscle volume and thigh muscle/fat ratio, as assessed by computed tomography [muscle volume (cm2/10 mm): 118.2 +/- 11.7 vs. 130.0 +/- 10.9 (P = 0.002); muscle/fat ratio: 1.33 +/- 0.24 vs. 1.69 +/- 0.36 (P = 0.02)]. In conclusion, discontinuation of GH treatment in GHD patients, during the transition from childhood to adulthood, induces significant and potentially unfavorable changes in IGF-I and body composition, both of which are reversed after resumption of GH treatment. By contrast, continuation of GH therapy results in unaltered IGF-I and body composition. We recommend continuation of GH therapy in these patients, to be undertaken in collaboration between pediatricians and adult endocrinologists.

Effects of growth hormone on bone and muscle

The decade since the initial availability of recombinant growth hormone (GH) has seen an increase in our understanding of the effects of GH on muscle and bone. Adult GH deficiency (GHD) is associated with osteopenia, the severity of which is related to three factors: the timing, age of onset and severity of GHD. Epidemiological data suggest that this osteopenia is associated with an increased risk of fracture. The impact of GH replacement therapy on bone mineral density (BMD) appears to be related to a large number of interrelated factors, including the dose and duration of therapy, timing of onset of GHD, skeletal site, degree of osteopenia at baseline, and age and gender of the patient. Overall, the effect of GH replacement on BMD in the majority of patients is beneficial. As yet, however, no data are available that demonstrate a reduction in fracture rate following GH therapy. In comparison with normal individuals, GH-deficient individuals have reduced lean body mass and muscle strength, both of which increase within 12 months of GH therapy. Therefore, the effects of GH replacement on muscle and bone in GH-deficient individuals are significant and beneficial, although the longer-term effects of GH replacement in terms of reducing the number of fractures and prevention of frailty in old age are not yet established. The effects of GH on bone and muscle in GH-replete individuals have been studied less fully. While GH therapy modulates markers of bone resorption and formation, its effects in patients with idiopathic osteoporosis are disappointing, with oestrogen therapy or bisphosphonates proving to be more effective in post-menopausal women. To date, however, there have been no GH treatment trials of adequate duration (longer than 18 months), and it remains possible that longer-term trials may demonstrate more profound effects. The effects of GH therapy on muscle have been examined in normal elderly individuals. Generally, the doses used have been supraphysiological and associated with an unacceptable incidence of side-effects. GH therapy has resulted in an increase in lean body mass, but functional ability and strength have not improved in the majority of studies. Thus, clear-cut beneficial effects of GH on muscle and bone in GH-replete individuals have not been demonstrated. It seems unlikely that normal elderly individuals will benefit significantly from GH therapy, but frail individuals or those with musculoskeletal or neuromuscular pathology are potential candidates for study.

Withdrawal of long-term physiological growth hormone (GH) administration: differential effects on bone density and body composition in men with adult-onset GH deficiency

Adults with acquired GH deficiency (GHD) have been shown to have osteopenia associated with a 3-fold increase in fracture risk and exhibit increased body fat and decreased lean mass. Replacement of GH results in decreased fat mass, increased lean mass, and increased bone mineral density (BMD). The possible differential effect of withdrawal of GH replacement on body composition compartments and regional bone mass is not known. We performed a randomized, single blind, placebo-controlled 36-month cross-over study of GH vs. placebo (PL) in adults with GHD and now report the effect of withdrawal of GH on percent body fat, lean mass, and bone density, as measured by dual energy x-ray absorptiometry. Forty men (median age, 51 yr; range, 24-64 yr) with pituitary disease and peak serum GH levels under 5 microg/L in response to two pharmacological stimuli were randomized to GH therapy (starting dose, 10 microg/kg x day, final dose 4 microg/kg x day) vs. PL for 18 months. Replacement was provided in a physiological range by adjusting GH doses according to serum insulin-like growth factor I levels. After discontinuation of GH, body fat increased significantly (mean +/- SEM, 3.18 +/- 0.44%; P = 0.0001) and returned to baseline. Lean mass decreased significantly (mean loss, 2133 +/- 539 g; P = 0.0016), but remained slightly higher (1276 +/- 502 g above baseline; P = 0.0258) than at study initiation. In contrast to the effect on body composition, BMD did not reverse toward pretreatment baseline after discontinuation of GH. Bone density at the hip continued to rise during PL administration, showing a significant increase (0.0014 +/- 0.00042, g/cm2 x month; P = 0.005) between months 18-36. Every bone site except two (radial BMD and total bone mineral content), including those without a significant increase in BMD during the 18 months of GH administration, showed a net increase over the entire 36 months. Therefore, there is a critical differential response of the duration of GH action on different body composition compartments. Physiological GH administration has a persistent effect on bone mass 18 months after discontinuation of GH.

Survivors of childhood cancer: long-term endocrine and metabolic problems dwarf the growth disturbance

The long-term effects of radiotherapy and chemotherapy are becoming increasingly recognized as the cure rates of certain childhood malignancies improve. The endocrine system is particularly sensitive to cancer therapies. Long-term survivors of childhood cancer who received cranial irradiation have been shown to have lower than predicted height, an increased prevalence of obesity and reductions in strength, exercise tolerance, bone mineral density, quality of life and academic achievement. Growth hormone deficiency (GHD) is the most frequent endocrine deficiency observed following cranial irradiation. Adults with GHD resulting from primary hypothalamic-pituitary disease during childhood have been shown to exhibit a clinical picture similar to that described in long-term survivors of childhood cancer: increased fat mass and reduced lean mass, strength, exercise tolerance, bone mineral density and quality of life. This review considers the possible contribution of GHD to the adverse sequelae observed in long-term survivors of childhood malignancy and includes our preliminary experience in treating 14 adults with GHD resulting from the treatment of childhood malignancies.

Discontinuation of growth hormone (GH) treatment: metabolic effects in GH-deficient and GH-sufficient adolescent patients compared with control subjects. Swedish Study Group for Growth Hormone Treatment in Children

The need for continuing GH replacement in patients with childhood-onset GH deficiency continuing into adulthood has been recognized. The metabolic consequences of discontinuing GH in adolescent patients with childhood-onset GH deficiency and short stature were examined over a period of 2 yr. Forty adolescents (aged 16-21 yr) receiving GH treatment for more than 3 yr and 16 closely matched healthy controls were studied. After a baseline visit, GH treatment was discontinued. The patients were then examined with the same protocol once a year for 2 yr. Twenty-one patients had severe GH deficiency (GHD) into adulthood, whereas 19 patients were regarded as having sufficient endogenous GH secretion (GHS). After 2 yr without GH treatment, the serum insulin-like growth factor I level was lower in GHD than in both GHS and control subjects. Both before and 2 yr after GH treatment was discontinued, serum concentrations of total cholesterol (C), low density lipoprotein C, and apolipoprotein B were higher in the GHD than in both GHS and control subjects. Serum concentrations of high density lipoprotein C decreased in the GHD group and increased in the other 2 study groups. The amount of total body and abdominal fat mass throughout the study and the increment in these masses were more marked in the GHD than in the GHS and control subjects when GH treatment was discontinued. The discontinuation of GH therapy in adolescents with severe GHD continuing into adulthood results over a period of 2 yr in the accumulation of important cardiovascular risk factors that are associated with GHD in adults.

Unfavourable impact of growth hormone (GH) discontinuation on body composition and cholesterol profiles after the completion of height growth in GH-deficient young adults

AIM

Growth hormone (GH) plays an important role in the regulation of body composition and metabolism. GH deficiency is associated with obesity and hypercholesterolemia, which respond to GH treatment. In this study we evaluated changes in body composition and cholesterol profiles after discontinuation of GH therapy to assess atherogenic risk factors in GH-deficient patients.

METHODS

We studied 18 male patients with GH deficiency 17-20 years of age at the time of discontinuing GH therapy. Body composition and cholesterol were measured 6 months before discontinuation of GH therapy with a weekly dose of 0.5 IU/kg (approximately 0.19 mg/kg), and immediately, 2 months, and 6 months after the end of GH therapy.

RESULTS

Two months after termination of GH therapy the percentage of body fat and fat mass increased from 7.4% to 9.4% and from 3.8 kg to 5.0 kg, respectively, and remained high thereafter. Lean body mass decreased gradually, but the change was not significant. Lean body mass: fat mass ratio decreased from 14.7 at termination of GH therapy to 10.9 at the end of study. Total cholesterol (TC) showed a significant linear increase from 156 mg/dl immediately after discontinuation to 169 mg/dl 6 months after discontinuation of GH, whereas high-density lipoprotein cholesterol (HDLC) showed no change during the study. The TC to HDLC ratio showed a slight but insignificant trend toward an increase. There were no significant changes in any variables during the last 6 months of GH therapy.

CONCLUSION

GH therapy in patients with GH deficiency can reduce risk factors for obesity-related diseases and atherosclerosis. These beneficial effects are reversed after discontinuation of GH therapy. Further long-term studies of the effects of the GH withdrawal on lipid profiles, adiposity and life expectancy must be performed.

Changes in muscle volume, strength, and bioenergetics during recombinant human growth hormone (GH) therapy in adults with GH deficiency

Adults with GH deficiency (GHD) suffer from muscle weakness, which can be caused by the frequently reported decrease in muscle mass. However, measurements of both muscle strength and mass of muscle tested are scarce in adults with GHD. The aim of the present study was, therefore, to investigate intrinsic muscle strength (strength expressed per muscle volume unit) in adults with GHD at baseline and after 52 weeks of recombinant human GH (rhGH) therapy given in low, more physiological doses. A second objective was to investigate the influence of GH on muscle bioenergetics in the resting muscle. Isometric and isokinetic quadriceps strengths were measured in 28 males with GHD and in healthy controls matched for age and height. Quadriceps mass, determined by magnetic resonance imaging, and muscle bioenergetics, determined by phosphorus nuclear magnetic resonance spectroscopy, were measured in 20 of 28 patients with GHD and in controls matched for age and height. All patients were treated with doses of rhGH ranging from 0.6-1.8 IU/day, given for 52 weeks. Measurements of muscle mass, strength, and bioenergetics were repeated after 52 weeks of treatment with rhGH. The mean GH dose at 52 weeks of rhGH treatment was 1.3 +/- 0.8 IU/day. The mean serum insulin-like growth factor I level at baseline was 9.4 +/- 0.7 nmol/L and significantly increased to 26.4 +/- 1.2 nmol/L after 52 weeks of rhGH treatment. Adults with GHD had significantly reduced quadriceps muscle mass (P = 0.034) and reduced isometric muscle strength (P = 0.002) and tended to have low isokinetic muscle strength (P = 0.06), which all improved after rhGH therapy. Intrinsic muscle strength was not significantly different in adults with GHD compared with that in healthy controls and did not change during rhGH therapy. No bioenergetic abnormalities at baseline or after rhGH therapy were found in males with GHD. In conclusion, quadriceps muscle mass is decreased in adults with GHD and increased with rhGH therapy. These changes in muscle mass account for the changes in muscle strength found in these patients, as no changes in intrinsic muscle strength were found.

Effects of hypophysectomy and growth hormone administration on the mRNA levels of collagen I, III and insulin-like growth factor-I in rat skeletal muscle

The effect of short-term treatment of normal or hypophysectomized rats with biosynthetic growth hormone (GH) was studied in extensor digitorum longus and soleus muscles. In situ hybridization revealed that in normal rats, mRNA for collagen I, collagen III and insulin-like growth factor-I (IGF-I) are expressed by fibroblasts between the muscle fibre areas and that the specificity of this location was not altered by GH administration. Hypophysectomy appeared to cause a decrease in IGF-I and decreased collagen I and III gene expression (P < 0.001, P < 0.001, respectively). GH administration seemed to increase IGF-I mRNA levels in all the animals studied. Quantitative image analysis that GH administration to hypophysectomized rats caused an increase in collagen I gene expression after 2 days (P < 0.05) and an increase in collagen III gene expression after 4 days (P < 0.05). The results indicate that the fibroblast cells are an important target for the action of GH on skeletal muscle and that the fibroblasts respond to GH by increases in the expression of mRNA for collagen I and collagen III.

How is whole body protein turnover perturbed in growth hormone-deficient adults?

Adult patients with GH deficiency have reduced lean body mass (LBM), muscle mass, and muscle strength, suggesting an underlying abnormality of protein metabolism. As acute GH administration has previously been reported to decrease protein oxidation and increase protein synthesis in GH-deficient (GHD) adults, we investigated whether the converse might occur in untreated GH deficiency by undertaking studies of whole body protein turnover in 10 GHD and 13 normal subjects using a 3-h primed constant infusion of 1-[13C]leucine. Dual energy x-ray absorptiometry was used to quantify LBM and fat mass (FM). In normal subjects, LBM was the major, independent determinant of leucine appearance (Ra; r=0.80; P=0.0009), leucine oxidation (r=0.81; P=0.0008), and leucine incorporation into protein (r=0.75; P= 0.003). However, in an analysis of covariance, FM was also a significant independent determinant of leucine Ra (P=0.002) and leucine incorporation into protein (P=0.003). After correcting for LBM and FM, GHD patients had significantly reduced rates of leucine Ra (109.9+/-4.4 vs. 125.5+/-3.7 micromol/min, respectively; P=0.02) and leucine incorporation into protein (87.0+/-3.9 vs. 100.3+/-3.3 mmol/ min; P=0.02) compared to normal subjects. There was no significant difference in the corrected rates of leucine oxidation between the two groups (22.9+/-1.3 vs. 25.2+/-1.0, GHD vs. normal; P=0.20). In summary, GHD adults have reduced rates of protein synthesis and protein breakdown, but normal rates of irreversible oxidative loss; these findings are discordant with what was predicted from the acute changes in protein metabolism observed with GH administration. We conclude that normalization of protein oxidation may be a homeostatic mechanism that operates to constrain protein loss in GHD adults.

Consequences of stopping growth hormone (GH) therapy in young GH deficient patients with childhood onset disease

Many studies have shown the beneficial, anabolic effects of growth hormone (GH) replacement therapy in GH deficient adults with childhood onset or adult onset disease. It is becoming increasingly evident, however, that these two groups of patients differ in many respects. Patients with adult onset GH deficiency represent fully developed individuals who have various organic, cerebral defects. By contrast, patients with childhood onset disease represent a heterogenous group comprising individuals with conditions, such as idiopathic isolated GH deficiency, genetic defects and organic defects. It is generally accepted that all children treated with GH should be retested in adulthood before adult replacement is started, as around 40% have a normal retest. It is unclear whether continued treatment with GH in childhood onset GH deficiency will yield results as positive as those seen in trials where GH is re-instituted after longer periods without treatment. Similarly, it is unknown at what timepoint cessation of GH treatment will cause a worsening in the physical state of the patient. In our placebo-controlled trial where GH was discontinued in 19 patients treated with GH during childhood, we determined exercise capacity, body composition, muscle mass and strength, cardiac function, sweating capacity, thyroid function and glucose metabolism before and after 12 months of continued treatment with GH.

Effects of recombinant growth hormone (GH) treatment on bone mineral density and body composition in adults with childhood onset growth hormone deficiency

Lumbar spine, whole proximal femur and total body bone mineral density (BMD, g/cm2) and the regional soft tissue composition were measured with dual energy X-ray absorptiometry (Hologic QDR 1000/W) in eight adults with childhood onset GHD, before and after 6 months of recombinant GH treatment (0.5 IU/kg/week). Data obtained from patients were compared with those recorded in an age and sex matched control group. Before treatment, lumbar (L2-L4) spine BMD (mean +/- SD: 0.811 +/- 0.159 g/cm2), whole proximal femur BMD (0.739 +/- 0.094 g/cm2) and total body BMD (0.946 +/- 0.087 g/cm2) of patients were significantly (p < 0.001, 0.01 and 0.001, respectively) lower than those recorded in an age- and sex-matched control group (1.077 +/- 0.155 g/cm2, 0.968 +/- 0.166 g/cm2 and 1.168 +/- 0.058 g/cm2, respectively), although three patients showed BMD values at the lower limit of the normal range. Mean lumbar spine BMD, whole proximal femur BMD and total body BMD did not significantly change alter 6 months' GH treatment (-1.4 +/- 3.7%, +2.7 +/- 3.7% and -1.1 +/- 5.0% vs basal values, respectively). On the other hand, trochanteric subregion showed a significant 4.8 +/- 5.3% increase (vs basal, p < 0.05), while other hip subregions did not show significant changes. GH therapy caused marked effects on body composition; in fact, a significant decrease (p < 0.01) of trunk fat (-25.2 +/- 15.0%) and a marked increase (p < 0.01) of limbs lean mass (+10.0 +/- 5.3%), resulting in a significant (p < 0.02) reduction (-16.5 +/- 13.5%) of the axial to peripheral fat ratio (APFR), were clearly evident after six months of therapy. In conclusion, our study shows that six months of GH treatment do not exert relevant effects on the BMD of adults with childhood onset GHD. On the contrary, the effects of GH therapy on body composition are more marked, being clearly appreciable after six months of treatment.

Improved left ventricular function after growth hormone replacement in patients with hypopituitarism: assessment with radionuclide angiography

Prolonged growth hormone deficiency (GHD) leads to marked cardiac dysfunction; however, whether reversal of this abnormality may be achieved after specific replacement therapy has not yet been completely clarified. Fourteen patients with childhood-onset GHD (nine men and five women, mean age 27+/-4 years) and 12 normal control subjects underwent equilibrium radionuclide angiography under control conditions at rest. Patients with GHD were also studied 6 months after recombinant human (rh) GH treatment (0.05 IU/kg per day). Normal control subjects and patients with GHD did not differ with respect to age, gender and heart rate. In contrast, left ventricular ejection fraction (53%+/-9% vs 66%+/-6%, P <0.001), stroke volume index (41+/-11 vs 51+/-8 ml/m2, P <0.01) and cardiac index (2.8+/-0.6 vs 3.+/-0.5 l/min/m2, P <0.001) were significantly lower in GHD patients than in normal control subjects. None of the GHD patients showed adverse or side-effects during rhGH therapy; thus none required a reduction in GH dose during the treatment period. Heart rate and arterial blood pressure were not significantly modified by rhGH treatment. After 6 months of rhGH therapy a significant improvement in left ventricular ejection fraction (from 53%+/-9% to 59%+/-9%, P <0.01), stroke volume index (from 41+/-11 to 47+/-13 ml/m2, P <0.05) and cardiac index (from 2.8+/-0.6 to 3.3+/-0.8 l/min/m2, P <0.01) was observed in GHD patients. In conclusion, prolonged lack of GH leads to impaired left ventricular function at rest. Reversal of this abnormality may be observed after 6 months of specific replacement therapy in patients with childhood-onset GHD.

Growth hormone increases IGF-I, collagen I and collagen III gene expression in dwarf rat skeletal muscle

The effect of short-term treatment with biosynthetic growth hormone (GH) of male dwarf rats was studied in EDL and soleus muscles. In situ hybridisation revealed that in the untreated dwarf rat collagen I, collagen III and insulin-like growth factor-I (IGF-I) mRNA is mainly expressed by fibroblasts between the muscle fibre areas. Quantitative image analysis showed that, 8 h after a single GH injection, the level of mRNA for all three genes increased compared to the untreated dwarf animal. IGF-I mRNA levels were similar in normals and untreated dwarf rats but significantly increased 8 h after a single GH injection in EDL (P < 0.01) and soleus (P < 0.001). In untreated dwarf rats, collagen I and III gene expression was significantly less than in normal animals (P < 0.001). Collagen III gene expression also increased significantly 8 h after a single GH injection, in both muscles (P < 0.01). Collagen I gene expression showed significant increases 8 and 24 h after GH treatment in EDL (P < 0.01), although the increases seen in soleus did not reach significance. The effects of multiple GH injections (one, two or four) did not appear to be additive. The results of the time course studies are consistent with an intermediary role for IGF-I in the production of collagen in muscle.

Abnormal body composition and reduced bone mass in growth hormone deficient hypopituitary adults

OBJECTIVES

The role of growth hormone in maintaining normal body composition and bone strength in adults has attracted much interest recently. We have assessed body composition and bone mass in GH deficient hypopituitary adults on conventional replacement therapy and compared them with matched controls.

DESIGN AND SUBJECTS

A cross-sectional study of 64 growth hormone deficient hypopituitary adults (29 males and 35 females) on conventional replacement therapy and a large number of healthy control subjects matched for age, sex and body mass index (BMI).

MEASUREMENTS

Skinfold thicknesses at two sites (triceps and subscapular), waist and hip girth circumferences were assessed by standard methods. Body composition was assessed using total body potassium (TBK), bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DEXA). Bone mineral mass was assessed at the lumbar spine and the total body by DEXA. Not every patient and control participated in every measurement.

RESULTS

Obesity was common in the hypopituitary patients; BMI (mean +/- SD) was 27.5 +/- 4.6 kg/m2 and body weight was 111.8 +/- 18.5% of the maximal ideal for height (P < 0.001). The sum of subscapular and triceps skinfolds was significantly higher in hypopituitary patients than in controls (men 46 + 15 vs 37 +/- 14 mm, P < 0.05; women 55 +/- 13 vs 47 +/- 17 mm, P < 0.05). Waist to hip circumference ratio was significantly greater in female hypopituitary patients than in matched controls but was not significantly different in men (men 0.94 +/- 0.07 vs 0.91 +/- 0.07, NS; women 0.84 +/- 0.09 vs 0.77 +/- 0.05, P < 0.001). The difference between patients and controls in the sum of skinfolds and the waist to hip ratio were present in non-obese (BMI < 26 kg/m2) subjects (21 patients and 32 controls). TBK corrected for body weight was significantly lower in hypopituitary patients (n = 44) than in controls (n = 31) (men 43.5 +/- 5.6 vs 50.1 +/- 5.9 mmol/kg, P < 0.003; women: 34.0 +/- 3.2 vs 40.6 +/- 5.3 mmol/kg, P < 0.0001). BIA-derived body water content (corrected for body weight) was significantly lower in hypopituitary patients (n = 56) than in controls (n = 57) (0.492 +/- 0.064 vs 0.545 +/- 0.067 l/kg, P < 0.0004). Percentage body fat derived from all the three methods was significantly higher in hypopituitary patients than in normal controls in both sexes (from TBK: men 34.7 +/- 9.4 vs 28.8 +/- 7.0%, P < 0.05; women 37.8 +/- 8.7 vs 30.4 +/- 9.7%, P < 0.01; from BIA: men 29.3 +/- 8.5 vs 23.2 +/- 8.4%, P < 0.01; women 34.6 +/- 8.1 vs 29.3 +/- 9.1% P < 0.01; and from DEXA: men 24.8 +/- 6.8 vs 20.4 +/- 6.1%, P < 0.05; women 38.9 +/- 7.9 vs 32.5 +/- 9.8%, P < 0.01). There was a significant difference between non-obese patients and controls in BIA-derived percentage fat in both sexes and in TBK-derived percentage fat in females only. Bone mineral density (BMD) of the lumbar spine in the L2-L4 region was lower in hypopituitary patients than in controls (men 1.116 +/- 0.129 vs 1.311 +/- 0.131 g/cm2, P < 0.0001; women 1.001 +/- 0.122 vs 1.131 +/- 0.138 g/cm2, P < 0.001). Spine BMD was also reduced in hypopituitary patients compared to the young adult and age and weight matched reference data. Total body BMD was significantly lower in patients than in controls (men 1.186 +/- 0.102 vs 1.250 +/- 0.080 g/cm2, P < 0.05; women 1.080 +/- 0.077 vs 1.149 +/- 0.073 g/cm2, P < 0.005).

CONCLUSIONS

Hypopituitary adults on conventional therapy have abnormal body composition with increased fat content, reduced body water content and reduced bone mineral mass.

Replacement treatment with biosynthetic human growth hormone in growth hormone-deficient hypopituitary adults

OBJECTIVES

The physiological role of growth hormone in adult life has recently attracted increased interest. We have studied the clinical effects and the effects on body composition of prolonged replacement with biosynthetic human GH in a large number of hypopituitary adults.

DESIGN

A randomized double blind placebo controlled trial for 6 months followed by an open trial of GH treatment for 12 months. GH daily dose was 0.04 (0.02-0.05) IU/kg s.c.

PATIENTS

Forty GH deficient hypopituitary patients (19 M, 21 F; aged 19-67 years) on conventional replacement therapy were studied.

MEASUREMENTS

Serum insulin like growth factor I (IGF-I), skinfold thickness, total body potassium, total body water (TBW), exercise tolerance and muscle strength, and well-being.

RESULTS

During the 6-month double blind phase, two GH treated patients withdrew because of adverse events. Lean body mass (LBM) increased and percentage body fat (%BF) decreased on GH but not on placebo (P) (LBM: (GH: from 48.5 +/- 9.6 to 49.6 +/- 9.5 kg; P: from 50.9 +/- 9.2 to 50.1 +/- 9.0 kg, P < 0.05 GH vs P) and %BF (GH: from 34.7 +/- 11.4 to 34.2 +/- 10.7; P: from 37.4 +/- 7.6 to 38.7 +/- 8.1, P < 0.05 GH vs P)). TBW increased on GH (P < 0.01) but not on P. No change was observed in waist-to-hip ratio or in muscle strength. During longer-term follow-up combining the double blind and open phase components of the study, 34, 27 and 11 patients received GH for 6, 12 and 18 months respectively. Patients dropped out because of adverse events or lack of perceived benefit. Skinfold thicknesses decreased significantly at 6 and 12 months and the waist circumference at 6 months. Waist-to-hip ratio decreased significantly on GH at 12 months. LBM increased on GH treatment from 49.6 +/- 9.1 to 51.6 +/- 9.4 kg (P < 0.0006), 51.9 +/- 8.9 kg (P < 0.07) and 53.1 +/- 10.5 kg (P < 0.0001) at 6, 12 and 18 months respectively. Percentage body fat decreased on GH from 37.2 +/- 10.7 to 34.7 +/- 10.1 (P < 0.005), 35.1 +/- 12.8 (NS) and 34.5 +/- 8.6 (P < 0.04) at 6,12 and 18 months respectively. TBW also increased at 6 and 12 months of GH treatment. Exercise time increased significantly at 6, 12 and 18 months of GH treatment. Muscle strength in selected muscle groups increased significantly at 6, 12 or 18 months of GH treatment. Randomization resulted in the placebo group having a greater GHQ score (higher morbidity) than the GH group before therapy. Over the controlled phase, GHQ scores improved on placebo but not on GH and CPRS score was unchanged in either group. In the open phase, the GHQ score did not change on GH therapy but CPRS score improved at 6 and 12 months.

CONCLUSIONS

Growth hormone replacement therapy in adults for 6 months increased lean body mass, total body water and exercise tolerance, and decreased body fat. Growth hormone replacement for longer than 6 months maintains the advantageous effects seen in shorter-term studies and may have additional effects on body fat distribution, muscle strength and psychological well-being.

Impaired cardiac performance in GH-deficient adults and its improvement after GH replacement

Cardiac performance was investigated by radionuclide angiography in 11 patients with childhood-onset growth hormone (GH) deficiency and in 12 control subjects. Both at rest and during maximal physical exercise, systolic function was markedly depressed in GH-deficient patients. Ejection fraction rose from 66 +/- 6 to 76 +/- 7% during exercise in control subjects, whereas in GH-deficient patients it remained unchanged or even decreased (55 +/- 6 and 54 +/- 9% at rest and after exercise, respectively; P < 0.01 vs. controls). Cardiac index was significantly lower in GH-deficient patients than in controls, both at rest (2.7 +/- 0.6 vs. 3.7 +/- 0.5 l.min-1.m-2; P < 0.001) and during exercise (8 +/- 1.2 vs. 10 +/- 1.5 l.min-1.m-2; P < 0.01). Five GH-deficient patients were treated with recombinant human (rh) GH for 6 mo at a dose of 0.05 IU.kg-1.day-1. Cardiac index at rest improved from 2.8 +/- 0.6 to 3.3 +/- 0.8 l.min-1.m-2 (P < 0.01) after rhGH. Also, cardiac index response to exercise improved markedly and became similar to that of controls (7.5 +/- 1.2 and 10.1 +/- 1.1 l.min-1.m-2 before and after rhGH, respectively; P < 0.005). Exercise tolerance was impaired in GH-deficient patients and was restored by rhGH treatment. The data support the hypothesis that GH plays an important role in the maintenance of a normal cardiac performance in humans.

Adipose tissue and muscle volume determination by computed tomography in acromegaly, before and 1 year after adenomectomy

The adipose tissue volume, skeletal muscle and skin volume and visceral organ volume were determined using the multiscan CT (computed tomography) technique in 15 patients with acromegaly. The examinations were performed before treatment and 1 year after transsphenoidal adenectomy. The mean body weight did not change significantly after treatment; 91.3 kg and 92.3 kg pre and postoperatively in men and 66.7 kg and 65.9 kg in women respectively. The total adipose tissue volume increased by 7.11 (59.2%, P < 0.01) in the male group and 3.9 1 (20.3%, P < 0.05) in the female group. Muscle and skin mass and visceral organ mass decreased significantly after treatment. The muscle and skin mass decreased by 3.6 1 (-7.4%, P < 0.01) in males and by 3.2 1 in females (-11.5%, P < 0.02). The corresponding decrease in visceral organ mass was 1.5 1 (-17.0%, P < 0.01) in males and 1.0 1 (15.4%, P < 0.05) in females respectively. On average, the fractions of adipose tissue in the subcutaneous trunk and the intra-abdominal depots increased after treatment, while the fractions of adipose tissue in the limbs and the head and neck region decreased. The change in adipose tissue distribution pattern reached significance (P < 0.005) in men only.