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

Sexual dimorphic impact of adult-onset somatopause on life span and age-induced osteoarthritis

Osteoarthritis (OA), the most prevalent joint disease, is a major cause of disability worldwide. Growth hormone (GH) has been suggested to play significant roles in maintaining articular chondrocyte function and ultimately articular cartilage (AC) homeostasis. In humans, the age-associated decline in GH levels was hypothesized to play a role in the etiology of OA. We studied the impact of adult-onset isolated GH deficiency (AOiGHD) on the life span and skeletal integrity including the AC, in 23- to 30-month-old male and female mice on C57/BL6 genetic background. Reductions in GH during adulthood were associated with extended life span and reductions in body temperature in female mice only. However, end-of-life pathology revealed high levels of lymphomas in both sexes, independent of GH status. Skeletal characterization revealed increases in OA severity in AOiGHD mice, evidenced by AC degradation in both femur and tibia, and significantly increased osteophyte formation in AOiGHD females. AOiGHD males showed significant increases in the thickness of the synovial lining cell layer that was associated with increased markers of inflammation (IL-6, iNOS). Furthermore, male AOiGHD showed significant increases in matrix metalloproteinase-13 (MMP-13), p16, and β-galactosidase immunoreactivity in the AC as compared to controls, indicating increased cell senescence. In conclusion, while the life span of AOiGHD females increased, their health span was compromised by high-grade lymphomas and the development of severe OA. In contrast, AOiGHD males, which did not show extended life span, showed an overall low grade of lymphomas but exhibited significantly decreased health span, evidenced by increased OA severity.

Body Composition Changes with Long-term Pegvisomant Therapy of Acromegaly

Context

In active acromegaly, the lipolytic and insulin antagonistic effects of growth hormone (GH) excess alter adipose tissue (AT) deposition, reduce body fat, and increase insulin resistance. This pattern reverses with surgical therapy. Pegvisomant treats acromegaly by blocking GH receptor (GHR) signal transduction and lowering insulin-like growth factor 1 (IGF-1) levels. The long-term effects of GHR antagonist treatment of acromegaly on body composition have not been studied.

Methods

We prospectively studied 21 patients with active acromegaly who were starting pegvisomant. Body composition was examined by whole body magnetic resonance imaging, proton magnetic resonance spectroscopy of liver and muscle and dual-energy x-ray absorptiometry, and endocrine and metabolic markers were measured before and serially during 1.0 to 13.4 years of pegvisomant therapy. The data of patients with acromegaly were compared with predicted and to matched controls.

Results

Mass of visceral AT (VAT) increased to a peak of 187% (1.56-229%) (P < .001) and subcutaneous AT (SAT) to 109% (–17% to 57%) (P = .04) of baseline. These remained persistently and stably increased, but did not differ from predicted during long-term pegvisomant therapy. Intrahepatic lipid rose from 1.75% to 3.04 % (P = .04). Although lean tissue mass decreased significantly, skeletal muscle (SM) did not change. IGF-1 levels normalized, and homeostasis model assessment insulin resistance and HbA1C were lowered.

Conclusion

Long-term pegvisomant therapy is accompanied by increases in VAT and SAT mass that do not differ from predicted, stable SM mass and improvements in glucose metabolism. Long-term pegvisomant therapy does not produce a GH deficiency-like pattern of body composition change.

The enigmatic role of growth hormone in age-related diseases, cognition, and longevity

Growth hormone (GH) is secreted by the anterior pituitary gland and regulates various metabolic processes throughout the body. GH and IGF-1 levels are markedly reduced in older humans, leading some to hypothesize GH supplementation could be a viable "anti-aging" therapy. However, there is still much debate over the benefits and risks of GH administration. While an early study of GH administration reported reduced adiposity and lipid levels and increased bone mineral density, subsequent studies failed to show significant benefits. Conversely, other studies found positive effects of GH deficiency including extended life span, improved cognitive function, resistance to diseases such as cancer and diabetes, and improved insulin sensitivity despite a higher fat percentage. Thus, the roles of GH in aging and cognition remain unclear, and there is currently not enough evidence to support use of GH as an anti-aging or cognitive impairment therapy. Additional robust and longer-duration studies of efficacy and safety of GH administration are needed to determine if modulating GH levels could be a successful strategy for treating aging and age-related diseases.

Functional Changes after Recombinant Human Growth Hormone Replacement in Patients with Chronic Traumatic Brain Injury and Abnormal Growth Hormone Secretion

We explored the effects of recombinant human growth hormone (rhGH) replacement on physical and cognitive functioning in subjects with a moderate-to-severe traumatic brain injury (TBI) with abnormal growth hormone (GH) secretion. Fifteen individuals who sustained a TBI at least 12 months prior to study enrollment were identified as having abnormal GH secretion by glucagon stimulation testing (maximum GH response less than 8 ng/mL). Peak cardiorespiratory capacity, body composition, and muscle force testing were assessed at baseline and one year after rhGH replacement. Additionally, standardized neuropsychological tests that assess memory, processing speed, and cognitive flexibility, as well as self-report inventories related to depression and fatigue, were administered at baseline and 1 year after rhGH replacement. Comparison tests were performed with proper post hoc analyses. All analyses were carried out at α < 0.05. Peak O₂ consumption, peak oxygen pulse (estimate of cardiac stroke volume), and peak ventilation all significantly increased (p < 0.05). Maximal isometric and isokinetic force production were not altered. Skeletal muscle fatigue did not change but the perceptual rating of fatigue was reduced by ∼25% (p = 0.06). Cognitive performance did not change significantly over time, whereas self-reported symptoms related to depression and fatigue significantly improved. The observed changes suggest that rhGH replacement has a positive impact on cardiorespiratory fitness and a positive impact on perceptual fatigue in survivors of TBI with altered GH secretion.

Detecting growth hormone misuse in athletes

Athletes have been misusing growth hormone (GH) for its anabolic and metabolic effects since the early 1980s, at least a decade before endocrinologists began to treat adults with GH deficiency. Although there is an ongoing debate about whether GH is performance enhancing, recent studies suggest that GH improves strength and sprint capacity, particularly when combined with anabolic steroids. The detection of GH misuse is challenging because it is an endogenous hormone. Two approaches have been developed to detect GH misuse; the first is based on the measurement of pituitary GH isoforms and the ratio of 22-kDa isoform to total GH. The second is based on the measurement of insulin like growth factor-I (IGF-I) and N-terminal propeptide of type III procollagen (P-III-NP) which increase in a dose-dependent manner in response to GH administration. Both methodologies have been approved by the World Anti-Doping Agency (WADA) and have led to the detection of a number of athletes misusing GH.

The vector of quadriceps pull is directed from the patella to the femoral neck

BACKGROUND

The quadriceps is the primary extensor of the knee. Its vector, which is perpendicular to the flexion axis of the knee, is important in understanding knee function and properly aligning total knee components. Three-dimensional (3-D) imaging enables evaluation using a 3-D model of each quadriceps component.

QUESTIONS/PURPOSES

We calculated the direction and magnitude of the quadriceps vector (QV) and the precision of the measurement, and asked whether the QV bears a constant relationship to the femur and is aligned with an anatomically based axis on the femur.

METHODS

Using CT data of 14 subjects, we created a 3-D solid model of each quadriceps muscle component. Vectors (3-D direction and length) for each quadriceps component were determined using principal component analysis for muscle direction and volume for magnitude; vector addition established the directional vector of the combined muscle. The combined vector originating in the center of the patella was compared with the shaft, mechanical, and spherical (center femoral head to center medial side of the knee) axes.

RESULTS

The QV passed from the patella center proximally crossing the femoral neck between the femoral head and greater trochanter and was most closely aligned with the spherical axis.

CONCLUSIONS

The QV axis may be an important reference for alignment of total knee components.

CLINICAL RELEVANCE

The spherical axis can be used in aligning total knee components to the flexion axis of the knee.

Skeletal muscle mass in acromegaly assessed by magnetic resonance imaging and dual-photon x-ray absorptiometry

CONTEXT

GH and IGF-I are nitrogen retaining and anabolic, but the impact of long-term exposure to supraphysiological GH and IGF-I, either from endogenous overproduction in acromegaly or exogenous sources, on skeletal muscle (SM) mass is not clear.

OBJECTIVES

The objectives of the study were to assess SM mass by whole-body magnetic resonance imaging (MRI) in acromegaly and test the hypothesis that dual-energy x-ray absorptiometry (DXA) lean tissue mass-derived estimates of SM accurately estimate true SM mass.

DESIGN, SETTING, AND PATIENTS

The design was a cross-sectional study in 27 acromegaly patients compared with predicted models developed in 315 nonacromegaly subjects and to matched controls.

OUTCOME MEASURES

Mass of SM from whole-body MRI and lean tissue from DXA were measured.

RESULTS

SM mass did not differ from predicted or control values in active acromegaly: 31.75 +/- 8.6 kg (acromegaly) vs. 33.06 +/- 8.9 kg (predicted); SM was 95.6 +/- 12.8% of predicted (range 66.7-122%) (P = 0.088). Lean tissue mass (DXA) was higher in acromegaly than controls: 65.91 +/- 15.2 vs. 58.73 +/- 13.5 kg (P < 0.0001). The difference between lean tissue mass (DXA) and SM in acromegaly patients was higher than that in controls (P < 0.0001) consistent with an enlarged non-SM lean compartment in acromegaly. SM mass predicted by DXA correlated highly with SM mass by MRI (r = 0.97, P < 0.0001). SM (MRI) to SM (DXA predicted) ratio was 1.018 (range 0.896-1.159), indicating high agreement of these measures of SM.

CONCLUSIONS

SM mass in active acromegaly patients did not differ from predicted values. SM mass estimated from DXA agreed highly with SM by MRI, supporting the validity of the DXA model in assessing SM in acromegaly and other disorders of GH/IGF-I secretion.

Self-dissolving micropiles for the percutaneous absorption of recombinant human growth hormone in rats

The feasibility of self-dissolving micropiles (SDMP) as a percutaneous delivery system of recombinant human growth hormone (rhGH) has been studied in rats using SDMP where dextran was used as a base. After mixing dextran solution with rhGH, SDMPs were prepared by pulling with polypropyrene tips. The mean weight, length and diameter were 0.68+/-0.05 mg, 3.2+/-0.5 mm and 0.6+/-0.2 microm, respectively. To evaluate the bioavailability (BA) of rhGH percutaneously administered by SDMP, an absorption experiment was performed in rats. RhGH SDMPs were inserted into the rats skin, 200 microg kg(-1), and plasma rhGH levels were measured by an ELISA method. Peak plasma rhGH level, 132.8+/-11.8 ng ml(-1), appeared at 0.8+/-0.2 h. By comparing the plasma rhGH levels vs. time profiles after the administration of SDMP and intravenous injection of rhGH solution, 5 microg kg(-1), BA of rhGH from SDMP was calculated to be 87.5%. Theses results may suggest that SDMP can be used as a novel percutaneous drug delivery system.

Efficacy of needle-free administration of recombinant human growth hormone in adults with growth hormone deficiency

AIM

Needle-free administration of recombinant human growth hormone (rhGH) is effective in the treatment of growth hormone deficiency (GHD) in children, but has not been studied in adult patients. Therefore, we evaluated the efficacy of needle-free administration of rhGH in adults with GHD.

METHODS

Insulin-like growth factor-I (IGF-I) concentrations were compared in newly diagnosed patients with GHD (n = 21) and in patients previously treated by subcutaneous injection of rhGH (switchers, n = 34), at baseline, 12 months and 24 months.

RESULTS

In the new patients, IGF-I standard deviation scores (SDS) increased from - 1.82 +/- 0.46 to + 0.75 +/- 0.33 at 12 months and to + 0.65 +/- 0.41 at 24 months (P < or = 0.001 vs. baseline). In switchers, IGF-I SDS remained unchanged with values of + 0.98 +/- 0.32 at baseline, + 0.87 +/- 0.23 at 12 months and + 0.73 +/- 0.29 at 24 months (P = 0.696 vs. baseline). In new patients, the rhGH dose was 0.46 +/- 0.03 mg day(-1) at 12 months and 0.47 +/- 0.03 mg day(-1) at 24 months. In switchers, the rhGH dose was 0.53 +/- 0.04 mg day(-1) at baseline (s.c. injection), 0.52 +/- 0.03 mg day(-1) at 12 months and 0.48 +/- 0.03 mg day(-1) at 24 months (NS between the different time points). There was no difference in the dose of rhGH at 12 and 24 months between the two groups. Side-effects were generally minor and consisted of local tissue reactions.

CONCLUSION

Administration of rhGH by needle-free, transdermal injection is effective in maintaining IGF-I concentrations in the normal range for age in adults with GHD, and is as effective as traditional subcutaneous injection of rhGH.

Justified and unjustified use of growth hormone

Growth hormone (GH) replacement therapy for children and adults with proven GH deficiency due to a pituitary disorder has become an accepted therapy with proven efficacy. GH is increasingly suggested, however, as a potential treatment for frailty, osteoporosis, morbid obesity, cardiac failure, and various catabolic conditions. However, the available placebo controlled studies have not reported many significant beneficial effects, and it might even be dangerous to use excessive GH dosages in conditions in which the body has just decided to decrease GH actions. GH can indeed induce changes in body composition that are considered to be advantageous to GH deficient and non-GH deficient subjects. In contrast to GH replacement therapy in GH deficient subjects, however, excessive GH action due to GH misuse seems to be ineffective in improving muscle power. Moreover, there are no available study data to indicate that the use of GH for non-GH deficient subjects should be advocated, especially as animal data suggest that lower GH levels are positively correlated with longevity.

Effects of GH and insulin-like growth factor-I on body composition

In this review, different methods to estimate body composition are discussed shortly. The effects by GH on total and visceral fat mass, lean mass, muscle strength and body water are described. Gender differences in the sensitivity to GH administration are reviewed. Finally, a short description of the effects of insulin-like growth factor-I (IGF-I) administration on body composition has been included.