Decreased trabecular bone biomechanical competence, apparent density, IGF-II and IGFBP-5 content in acromegaly

Osteosarcopenia in acromegaly: reduced muscle quality and increased vertebral fat deposition

PURPOSE

Musculoskeletal disorders are among the most disabling comorbidities in patients with acromegaly. This study examined muscle and bone quality in patients with acromegaly.

METHODS

Thirty-three patients with acromegaly and nineteen age- and body mass index-matched healthy controls were included in the study. Body composition was determined using dual-energy X-ray absorptiometry. The participants underwent abdominal magnetic resonance imaging (MRI) for cross-sectional evaluation of muscle area and vertebral MRI proton density fat fraction (MRI-PDFF). Muscular strength was measured using hand grip strength (HGS). Skeletal muscle quality (SMQ) was classified as weak, low, or normal, according to HGS/ASM (appendicular skeletal muscle mass) ratio.

RESULTS

Groups had similar lean tissues, total body fat ratios, and total abdominal muscle areas. Acromegalic patients had lower pelvic BMD (p = 0.012) and higher vertebral MRI-PDFF (p = 0.014), while total and spine bone mineral densities (BMD) were similar between the groups. The SMQ score rate was normal only 57.5% in the acromegaly group, and 94.7% of the controls had a normal SMQ score (p = 0.01). Subgroup analysis showed that patients with active acromegaly (AA) had higher lean tissue and lower body fat ratios than controlled acromegaly (CA) and control groups. Vertebral MRI-PDFF was higher in the CA group than that in the AA and control groups (p = 0.022 and p = 0.001, respectively). The proportion of participants with normal SMQ was lower in the AA and CA groups than that in the control group (p = 0.012 and p = 0.013, respectively).

CONCLUSION

Acromegalic patients had reduced SMQ and pelvic BMD, but greater vertebral MRI-PDFF. Although lean tissue increases in AA, this does not affect SMQ. Therefore, increased vertebral MRI-PDFF in controlled acromegalic patients may be due to ectopic adiposity.

Differences between bone health parameters in adults with acromegaly and growth hormone deficiency: A systematic review

Preserving bone health is an important goal of care of patients with acromegaly and growth hormone deficiency (GHD). Both disorders are associated with compromised bone health and an increased risk of fracture. However, parameters of bone health that are routinely used to predict fractures in other populations, such as aBMD measured by DXA, are unreliable for this in acromegaly and GHD. Additional methodologies need to be employed to assess bone health in these patients. This review summarizes available data on the effects of acromegaly and GHD on parameters of bone health such as aBMD, volumetric bone mineral density (vBMD) and microarchitecture assessed by HRpQCT and other techniques, trabecular bone score (TBS) and fracture assessment. More research is needed to identify reliable predictors of fracture risk and to determine how best to screen for and treat those patients at risk so that bone health is optimized in these patients.

Endocortical Trabecularization in Acromegaly: The Cause for the Paradoxically Increased Vertebral Fracture Risk?

Growth hormone (GH) is nonphysiologically increased in acromegaly, stimulating target tissues directly and indirectly via insulin-like growth factor type 1 (IGF-1). Despite GH having anabolic effects on bone growth and renewal, the risk of vertebral fractures is paradoxically increased in acromegaly. We hypothesized that bone tissue compartments were differentially affected by hormonal alterations in active and controlled acromegaly. We aimed to study the effect of sex and gonadal status on long-term outcome of bone mass and structure to understand the biomechanical competence of bone. We followed 62 patients with newly diagnosed acromegaly longitudinally (median 4.8 years after pituitary surgery) to investigate changes assessed by dual X-ray absorptiometry (DXA), trabecular bone score (TBS), and hip structure analysis (HSA). At diagnosis, patients had increased bone mineral density (BMD) in most compartments compared with normative data (Z-scores). Conversely, TBS Z-score was decreased (Z = -0.64 (SD 1.73), p = 0.028). Following treatment of acromegaly, BMD increased further in compartments containing predominantly trabecular bone, such as the lumbar spine, in eugonadal and male subjects, while compartments with predominantly cortical bone, such as the hip and femoral neck, were unchanged. Total body measurements showed further increase in BMD independent of sex and gonadal status. TBS did not change. HSA revealed a significant decrease in cortical thickness in both sexes independent of gonadal status, whereas the overall size of bone (hip axis length and neck width) did not change over time. In conclusion, patients with acromegaly had increased bone mass and dimensions by DXA. Following normalization of disease activity, BMD increased mainly in compartments rich in trabecular bone, reflecting a closure of the remodeling space. However, HSA revealed a significant decrease in cortical thickness, implying endocortical trabecularization, potentially explaining the increased risk for incident vertebral fractures following treatment. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Bone quality in endocrine diseases: determinants and clinical relevance

PURPOSE

Bone is one of the main targets of hormones and endocrine diseases are frequent causes of secondary osteoporosis and fractures in real-world clinical practice. However, diagnosis of skeletal fragility and prediction of fractures in this setting could be a challenge, since the skeletal alterations induced by endocrine disorders are not generally captured by dual-energy X-ray absorptiometry (DXA) measurement of bone mineral density (BMD), that is the gold standard for diagnosis of osteoporosis in the general population. The aim of this paper is to review the existing evidence related to bone quality features in endocrine diseases, proposing assessment with new techniques in the future.

METHODS

A comprehensive search within electronic databases was performed to collect reports of bone quality in primary hyperparathyroidism, hypoparathyroidism, hyperthyroidism, hypercortisolism, growth hormone deficiency, acromegaly, male hypogonadism and diabetes mellitus.

RESULTS

Using invasive and non-invasive techniques, such as high-resolution peripheral quantitative computed tomography or DXA measurement of trabecular bone score (TBS), several studies consistently reported altered bone quality as predominant determinant of fragility fractures in subjects affected by chronic endocrine disorders.

CONCLUSIONS

Assessment of skeletal fragility in endocrine diseases might take advantage from the use of techniques to detect perturbation in bone architecture with the aim of best identifying patients at high risk of fractures.

Determinants of skeletal fragility in acromegaly: a systematic review and meta-analysis

PURPOSE

Vertebral fractures (VFs) are a potential complication in acromegaly. However, the etiology of this skeletal fragility is unknown. This review aimed to evaluate the effect of acromegaly on VFs, bone turnover, areal bone mineral density (aBMD), and bone quality/microarchitecture. The effect of disease activity and gonadal status in these determinants of skeletal fragility was also evaluated.

METHODS

Articles published in English until September 6, 2020 on PubMed and Embase that reported at least one determinant of skeletal fragility in acromegalic patients, were included. Odds ratio (OR) to evaluate the risk of VFs and the standardized mean difference (SMD) to evaluate bone turnover, aBMD and bone quality/microarchitecture were calculated.

RESULTS

Fifty-eight studies met eligibility criteria, assembling a total of 2412 acromegalic patients. Of these, 49 studies were included in the meta-analysis. Acromegalic patients, when compared to non-acromegalic patients, had higher risk of VFs [OR 7.00; 95% confidence interval (CI) 2.80-17.52; p < 0.0001], higher bone formation (SMD 1.14; 95% CI 0.69-1.59; p < 0.00001), higher bone resorption (SMD 0.60; 95% CI 0.09-1.10; p = 0.02) and higher aBMD at the femoral neck (SMD 0.36; 95% CI 0.15-0.57; p = 0.0009). No significant differences were found regarding aBMD at lumbar spine. Considering the results of the different techniques evaluating bone quality/microarchitecture, the main reported alterations were a decrease in trabecular bone thickness and density, and an increase in trabecular separation. The presence of active disease and/or hypogonadism were associated with worst results.

CONCLUSION

Patients with acromegaly are at increased risk of VFs, mainly because of deterioration in bone microarchitecture.

Lifelong Excess in GH Elicits Sexually Dimorphic Effects on Skeletal Morphology and Bone Mechanical Properties

Excess in growth hormone (GH) levels, seen in patients with acromegaly, is associated with increases in fractures. This happens despite wider bones and independent of bone mineral density. We used the bovine GH (bGH) transgenic mice, which show constitutive excess in GH and insulin-like growth factor 1 (IGF-1) in serum and tissues, to study how lifelong increases in GH and IGF-1 affect skeletal integrity. Additionally, we crossed the acid labile subunit (ALS) null (ALSKO) to the bGH mice to reduce serum IGF-1 levels. Our findings indicate sexually dimorphic effects of GH on cortical and trabecular bone. Male bGH mice showed enlarged cortical diameters, but with marrow cavity expansion and thin cortices as well as increased vascular porosity that were associated with reductions in diaphyseal strength and stiffness. In contrast, female bGH mice presented with significantly smaller-diameter diaphysis, with greater cortical bone thickness and with a slightly reduced tissue elastic modulus (by microindentation), ultimately resulting in overall stronger, stiffer bones. We found increases in C-terminal telopeptide of type 1 collagen and procollagen type 1 N propeptide in serum, independent of circulating IGF-1 levels, indicating increased bone remodeling with excess GH. Sexual dimorphism in response to excess GH was also observed in the trabecular bone compartment, particularly at the femur distal metaphysis. Female bGH mice preserved their trabecular architecture during aging, whereas trabecular bone volume in male bGH mice significantly reduced and was associated with thinning of the trabeculae. We conclude that pathological excess in GH results in sexually dimorphic changes in bone architecture and gains in bone mass that affect whole-bone mechanical properties, as well as sex-specific differences in bone material properties. © 2022 American Society for Bone and Mineral Research (ASBMR).

Trabecular Bone Score as a Reliable Measure of Lumbar Spine Bone Microarchitecture in Acromegalic Patients

Although GH and IGF-1 excess has a controversial impact on bone mineral density (BMD), acromegalic patients display variable degrees of bone structure impairment. In this study, we aim to investigate the usefulness of trabecular bone score (TBS), compared to BMD, in identifying acromegalic patients with impaired lumbar spine trabecular microarchitecture. Forty-four acromegalic patients were investigated for disease control, metabolic and gonadal status, bone metabolism parameters, and the presence of vertebral fractures (VFs). Patients and matched healthy controls underwent BMD and TBS examination. Mean TBS values were lower in patients than in controls (p < 0.001), without significant differences in mean lumbar and femoral BMD. TBS values were significantly higher in controlled patients compared to the uncontrolled ones (p = 0.012). No significant differences were found in bone markers with respect to disease control. Mean TBS or lumbar BMD did not significantly differ in patients with or without VFs (prevalence 11.4%). TBS and BMD levels were lower in hypogonadal patients compared to the eugonadal ones (p = 0.030 and p < 0.001, respectively). In conclusion, TBS values are significantly lower in patients than in controls, confirming the presence of impaired lumbar spine trabecular bone in acromegaly. Both uncontrolled disease and hypogonadism contribute to TBS deterioration in acromegaly.

Trabecular bone score and bone mineral density in acromegalic osteopathy assessment: a cross-sectional study

PURPOSE

The evaluation of acromegalic osteopathy is a subject of current interest as there is a lack of evidence concerning proper evaluation techniques and clear diagnostic criteria. The aim of this study was to evaluate lumbar spine trabecular bone score (TBS) and bone mineral density (BMD) in acromegaly patients compared to healthy controls.

METHODS

We conducted a cross-sectional study on 43 acromegaly patients recruited between 2018 and 2020 and a healthy control group matched 1:1 for age, gender, and body mass index (BMI). All subjects underwent DXA, lumbar spine TBS, and bone turnover markers measurement.

RESULTS

Acromegaly patients showed significantly decreased lumbar spine TBS (1.244 ± 0.117 vs. 1.343 ± 0.124, p < 0.001) and no difference regarding BMD compared to control patients. In the subgroup analysis, TBS was significantly lower in both males and females (1.282 ± 0.075 vs. 1.366 ± 0.113, p = 0.01 and 1.222 ± 0.132 vs. 1.329 ± 0.130, p = 0.005) and, also, in hypogonadal and eugonadal acromegaly subjects compared to their healthy controls (1.231 ± 0.130 vs. 1.306 ± 0.125, p = 0.04 and 1.280 ± 0.065 vs. 1.381 ± 0.113, p = 0.008). Femoral neck BMD was higher in acromegalic hypogonadal patients [1.027 (IQR: 0.939-1.135) vs. 0.876 (IQR: 0.737-1.014), p = 0.004].

CONCLUSION

Our study indicates that TBS, but not BMD, is significantly decreased in acromegaly patients, regardless of gender and gonadal status. This data suggests that TBS could be a valuable tool in the assessment of acromegalic osteopathy.

Trabecular bone score and bone mineral density in patients with long-term controlled acromegaly

OBJECTIVE

Acromegaly is associated with increased vertebral fracture (VFs) risk not correlated to bone mineral density (BMD). Trabecular bone score (TBS), related to bone microarchitecture, provides information on bone strength. This cross-sectional study considered the usefulness of TBS and BMD to assess bone status in long-term controlled acromegalic patients.

DESIGN, PATIENTS, MEASUREMENTS

26 acromegaly patients (14 female and 12 males) were included in the study. A further 117 subjects were recruited as controls (58 females and 57 males). BMD was measured using dual-energy X-ray absorptiometry (DXA), TBS was obtained applying Medimaps software 2.0. Biochemical parameters were determined by standardized techniques.

RESULTS

73% of patients with acromegaly exhibited normal lumbar spine (LS) BMD. TBS was normal in 38% of acromegalic patients and partially degraded or degraded in 31% of patients, respectively. No differences were found in LS BMD between acromegalic patients and controls. TBS values were significantly lower in patients with acromegaly (1.27 ± 0.13 vs. 1.35 ± 0.17, p = .01). Postsurgical remission was associated with higher TBS values (1.35 ± 0.10 vs. 1.23 ± 0.13, p = .02) and pituitary radiotherapy treatment with lower TBS values (1.18 ± 0.12 vs. 1.31 ± 0.12, p = .004). On multivariate analysis, age, BMI and LS BMD were predictors of TBS changes in patients with acromegaly (p < .05).

CONCLUSIONS

Patients with long-term controlled acromegaly can exhibit deterioration of bone microstructure measured with TBS, despite BMD measurement not showing bone loss. Our study suggests that TBS is useful for monitoring the bone status changes in acromegalic patients.

The intriguing giant deer from the Bate cave (Crete): could paleohistological evidence question its taxonomy and nomenclature?

The research describes for the first time a possible case of pituitary gigantism in fossil mammals, precisely in deer. The pathology was detected in 2 long bones (tibia and metatarsus) belonging to an individual of an unusual large size found at the Bate cave (Rethymnon, Northern Crete). It formed the basis of Candiacervus major, the largest among the endemic deer species recorded in the Pleistocene-Early Holocene of Crete. Radiological and histomorphological examinations highlighted a reduction in cortical bone thickness and the presence of wide lacunae inside of the bone tissue. The pathological conditions suggest a pituitary gigantism diagnosis also supported by some morphological evidence, such as the extremely elongated distal part of the metatarsal diaphysis, the proportionally small proximal epiphysis, and some bone gracility. The diagnosis of a case of pituitary gigantism as presumed responsible for the extraordinary elongation of the tibia and the metatarsal bone is intriguing as they are, respectively, the paratype and the holotype of the C. major. The species represents a case of a deviation from the "island rule" in Pleistocene large mammals. The new evidence recommends a taxonomic and nomenclatural revision of this species. The main outcomes of this research are as follows: (i) a case of pituitary gigantism is described for the first time in an extinct mammal; (ii) it is underlined that paleohistology may provide interesting clues for disentangling taxonomic and nomenclatural issues; (iii) one of the very few cases of gigantism in insular mammals is being questioned.

Hip Structure Analyses in Acromegaly: Decrease of Cortical Bone Thickness After Treatment: A Longitudinal Cohort Study

Long‐standing growth hormone (GH) excess causes the skeletal clinical signs of acromegaly with typical changes in bone geometry, including increased cortical bone thickness (CBT). However, a high prevalence and incidence of vertebral fractures has been reported. The aim of this study was to assess the course of cortical bone dimensions in the hip by comparing patients with acromegaly and clinically nonfunctioning pituitary adenomas (NFPAs) at baseline and 1 year after pituitary surgery (1‐year PO) in a longitudinal cohort study. DXA was performed in patients with acromegaly (n = 56) and NFPA (n = 47). CBT in the femoral neck (CBTneck), calcar (CBTcalcar), and shaft (CBTshaft) were determined by hip structural analysis (HSA). CBT at baseline and the change to 1‐year PO were compared. Test results were adjusted for differences in gender distribution, age, and gonadal status. Cortical thickness analyses showed higher values [mm] at baseline in patients with acromegaly compared with NFPA: CBTneck median [25th; 75th] 6.2 [4.7; 8.0] versus 5.1 [4.1; 6.4] (p = 0.006), CBTcalcar 4.8 [4.2, 5.7] versus 4.0 [3.2, 4.5] (p < 0.001), CBTshaft 6.2 [5.1, 7.2] versus 5.2 [4.6, 6.0], (p = 0.003). In acromegaly, GH was correlated with CBTneck (r = 0.31, p = 0.020), whereas IGF‐1 was correlated with CBTcalcar (r = 0.39, p = 0.003) at baseline. In acromegaly, CBTneck decreased by 11.2%, p = 0.002 during follow‐up. Finally, the decrease in CBTneck and CBTcalcar in acromegaly was significant compared with NFPA (p = 0.023 and p = 0.017, respectively). Previous observations of increased CBT in acromegaly were confirmed with DXA‐derived HSA in a large, well‐defined cohort. The decline in CBT in acromegaly could contribute to the increased fracture risk in acromegaly despite increased bone dimensions and disease control. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Pituitary Diseases and Bone

Neuroendocrinology of bone is a new area of research based on the evidence that pituitary hormones may directly modulate bone remodeling and metabolism. Skeletal fragility associated with high risk of fractures is a common complication of several pituitary diseases such as hypopituitarism, Cushing disease, acromegaly, and hyperprolactinemia. As in other forms of secondary osteoporosis, pituitary diseases generally affect bone quality more than bone quantity, and fractures may occur even in the presence of normal or low-normal bone mineral density as measured by dual-energy X-ray absorptiometry, making difficult the prediction of fractures in these clinical settings. Treatment of pituitary hormone excess and deficiency generally improves skeletal health, although some patients remain at high risk of fractures, and treatment with bone-active drugs may become mandatory. The aim of this review is to discuss the physiological, pathophysiological, and clinical insights of bone involvement in pituitary diseases.

Insulin-like growth factors: actions on the skeleton

The discovery of the growth hormone (GH)-mediated somatic factors (somatomedins), insulin-like growth factor (IGF)-I and -II, has elicited an enormous interest primarily among endocrinologists who study growth and metabolism. The advancement of molecular endocrinology over the past four decades enables investigators to re-examine and refine the established somatomedin hypothesis. Specifically, gene deletions, transgene overexpression or more recently, cell-specific gene-ablations, have enabled investigators to study the effects of the Igf1 and Igf2 genes in temporal and spatial manners. The GH/IGF axis, acting in an endocrine and autocrine/paracrine fashion, is the major axis controlling skeletal growth. Studies in rodents have clearly shown that IGFs regulate bone length of the appendicular skeleton evidenced by changes in chondrocytes of the proliferative and hypertrophic zones of the growth plate. IGFs affect radial bone growth and regulate cortical and trabecular bone properties via their effects on osteoblast, osteocyte and osteoclast function. Interactions of the IGFs with sex steroid hormones and the parathyroid hormone demonstrate the significance and complexity of the IGF axis in the skeleton. Finally, IGFs have been implicated in skeletal aging. Decreases in serum IGFs during aging have been correlated with reductions in bone mineral density and increased fracture risk. This review highlights many of the most relevant studies in the IGF research landscape, focusing in particular on IGFs effects on the skeleton.

Bone histomorphometry in acromegaly patients with fragility vertebral fractures

CONTEXT

The high risk of vertebral fractures (VFs) in acromegaly patients despite normal bone mineral density (BMD) is well known. The reasons for this paradoxical finding of skeleton fragility are poorly understood due to the limited data on bone histomorphometry in acromegaly.

OBJECTIVE

This study aimed to analyze histomorphometric parameters including bone microarchitecture in acromegaly patients with VFs and normal BMD compared to normal subjects, and also to evaluate the differences between active and controlled acromegaly patients.

PATIENTS AND METHODS

Forty-seven acromegaly patients (17 active, 30 controlled), median (range) age 57 years (30-88) were evaluated for bone turnover, morphometric VFs and BMD by dual-energy X-ray absorptiometry at lumbar spine and hip; 12 patients with VFs and normal BMD underwent iliac crest bone biopsy; 12 biopsies were taken at the autopsy in healthy sex and age-matched control subjects.

RESULTS

The histomorphometric evaluation of acromegaly fractured patients was compared with that of normal controls and showed significantly reduced median (range) levels of bone volume/tissue volume (BV/TV: 15.37% (7.93-26.75) vs. 18.61% (11.75-27.31), p = 0.036), trabecular thickness (TbTh: 77.6 µm (61.7-88.3) vs. 82.7 µm (72.3-92.0) p = 0.045), with increased trabecular separation (TbSp: 536.4 µm (356.2-900.6) vs. 370.3 µm (377.1-546.3) p = 0.038) and increased cortical thickness (1268 μm (752-2521) vs. 1065 μm (851-1205) p = 0.025) and porosity (11.9% (10.2-13.3) vs. 4.8% (1.6-8.8) p = 0.0008). While active acromegaly patients showed histomophometric features of increased bone turnover, patients with controlled disease presented normal bone turnover with significantly lower osteoblastic activity, expressed as osteoblast number (p = 0.001), active osteoblasts and vigor (p = 0.014) in the presence of reduced osteocyte number (p = 0.008) compared to active disease.

CONCLUSIONS

The apparent paradox of bone fragility in acromegaly patients with a normal BMD can be explained by increased cortical thickness and porosity and reduced trabecular thickness with increased trabecular separation. These structural and microarchitectural abnormalities persist in the controlled phase of acromegaly despite bone turnover normalization. The main determinant of bone disease after hormonal control is severe osteoblastic dysfunction.

Bone material strength index as measured by impact microindentation is altered in patients with acromegaly

OBJECTIVE

Acromegaly is a rare disease caused by excess growth hormone (GH) production by the pituitary adenoma. The skeletal complications of GH and IGF-1 excess include increased bone turnover, increased cortical bone mass and deteriorated microarchitecture of trabecular bone, associated with a high risk of vertebral fractures in the presence of relatively normal bone mineral density (BMD). We aimed to evaluate tissue-level properties of bone using impact microindentation (IMI) in well-controlled patients with acromegaly aged ≥18 years compared to 44 controls from the outpatient clinic of the Centre for Bone Quality.

DESIGN AND METHODS

In this cross-sectional study, bone material strength index (BMSi) was measured in 48 acromegaly patients and 44 controls with impact microindentation using the osteoprobe.

RESULTS

Mean age of acromegaly patients (54% male) was 60.2 years (range 37.9-76.5), and 60.5 years (range 39.8-78.6) in controls (50% male). Patients with acromegaly and control patients had comparable BMI (28.2 kg/m² ± 4.7 vs 26.6 kg/m² ± 4.3, P = 0.087) and comparable BMD at the lumbar spine (1.04 g/cm² ± 0.21 vs 1.03 g/cm² ± 0.13, P = 0.850) and at the femoral neck (0.84 g/cm² ± 0.16 vs 0.80 g/cm² ± 0.09, P = 0.246). BMSi was significantly lower in acromegaly patients than that in controls (79.4 ± 0.7 vs 83.2 ± 0.7; P < 0.001).

CONCLUSION

Our data indicates that tissue-level properties of cortical bone are significantly altered in patients with controlled acromegaly after reversal of long-term exposure to pathologically high GH and IGF-1 levels. Our findings also suggest that methods other than DXA should be considered to evaluate bone fragility in patients with acromegaly.

Acromegalic osteopathy

Acromegalic osteopathy is an emerging complication of acromegaly characterized by increase in bone turnover, deterioration in bone microarchitecture and high risk of vertebral fractures. Vertebral fractures, as diagnosed by a radiological and morphometric approach, occur in about one-third of acromegaly patients in close relationship with duration of active disease. However, the prediction of vertebral fractures in this clinical setting is still a matter of uncertainty, since the pathogenesis of acromegalic osteopathy is multifactorial and fractures may occur even in presence of normal bone mineral density. In this narrative article, we summarize the pathophysiology and clinical aspects of acromegalic osteopathy.

High-resolution-cone beam tomography analysis of bone microarchitecture in patients with acromegaly and radiological vertebral fractures

Vertebral fractures are an emerging complication of acromegaly but their prediction is still difficult occurring even in patients with normal bone mineral density. In this study we evaluated the ability of high-resolution cone-beam computed tomography to provide information on skeletal abnormalities associated with vertebral fractures in acromegaly. 40 patients (24 females, 16 males; median age 57 years, range 25-72) and 21 healthy volunteers (10 females, 11 males; median age 60 years, range: 25-68) were evaluated for trabecular (bone volume/trabecular volume ratio, mean trabecular separation, and mean trabecular thickness) and cortical (thickness and porosity) parameters at distal radius using a high-resolution cone-beam computed tomography system. All acromegaly patients were evaluated for morphometric vertebral fractures and for mineral bone density by dual-energy X-ray absorptiometry at lumbar spine, total hip, femoral neck, and distal radius. Acromegaly patients with vertebral fractures (15 cases) had significantly (p < 0.05) lower bone volume/trabecular volume ratio, greater mean trabecular separation, and higher cortical porosity vs. nonfractured patients, without statistically significant differences in mean trabecular thickness and cortical thickness. Fractured and nonfractured acromegaly patients did not have significant differences in bone density at either skeletal site. Patients with acromegaly showed lower bone volume/trabecular volume ratio (p = 0.003) and mean trabecular thickness (p < 0.001) and greater mean trabecular separation (p = 0.02) as compared to control subjects, without significant differences in cortical thickness and porosity. This study shows for the first time that abnormalities of bone microstructure are associated with radiological vertebral fractures in acromegaly. High-resolution cone-beam computed tomography at the distal radius may be useful to evaluate and predict the effects of acromegaly on bone microstructure.

Treatment of acromegaly increases BMD but reduces trabecular bone score: a longitudinal study

CONTEXT

Bone turnover is increased in acromegaly. Despite normalization of bone turnover after treatment, the risk for vertebral fractures remains increased. Gonadal status, but not BMD, is correlated with vertebral fractures. Trabecular bone score (TBS) is related to bone microarchitecture.

OBJECTIVE

The aim of this study is to assess the longitudinal change in TBS and BMD following treatment for acromegaly. DESIGN, SETTING, PATIENTS, INTERVENTIONS, AND MAIN OUTCOME MEASURES: This longitudinal study included 48 patients with acromegaly between 2005 and 2015. BMD, TBS, and markers for bone turnover (P1NP and CTX-1) were measured at baseline and following treatment.

RESULTS

Following treatment, the mean TBS decreased by 3.0 (±7.0) %, whereas the BMD at the lumbar spine (LS) increased by 3.2 (±4.9) % (both P<0.01). The changes in BMD LS and TBS were not correlated (P=0.87). The TBS change was found to be -4.5 % (±6.7; P=0.003) in men and -0.3 % (±6.8; P=0.85) in women (P=0.063 for interaction men vs women). The mean BMD LS increased in men +4.2 g/cm(2) (±4.3; P<0.001), but not in women +1.5 g/cm(2) (±5.6; P=0.36); (P=0.073 for interaction). BMD increased in the ultradistal radius and total body (both P<0.01). The increase in BMD LS was associated with a decrease in P1NP and CTX-1 (P<0.001) and with lower P1NP and CTX-1 at the follow-up (P<0.02).

CONCLUSION

Treatment of acromegaly affects TBS and BMD at LS in different manners. The reduction of bone turnover markers predicts the increase in BMD but not the decrease in TBS. The DXA changes were more pronounced in men. Alterations in trabecular bone architecture may explain the persistent fracture risk despite the increase in BMD after disease control.

Fractures in pituitary adenoma patients from the Dutch National Registry of Growth Hormone Treatment in Adults

PURPOSE

The effects of growth hormone (GH) replacement therapy on fracture risk in adult GH deficient (GHD) patients with different etiologies of pituitary GHD are not well known, due to limited data. The aim of this study was to investigate characteristics and fracture occurrence at start of (baseline) and during long-term GH replacement therapy in GHD adults previously treated for Cushing's disease (CD) or acromegaly, compared to patients with previous nonfunctioning pituitary adenoma (NFPA).

METHODS

From the Dutch National Registry of Growth Hormone Treatment in Adults, a nationwide surveillance study in severe GHD adults, all patients using ≥30 days of GH replacement therapy with previous NFPA (n = 783), CD (n = 180) and acromegaly (n = 65) were selected. Patient characteristics, fractures and potential influencing factors were investigated.

RESULTS

At baseline, patients with previous CD were younger, more often female and had more often a history of osteopenia or osteoporosis, whereas patients with previous acromegaly had more often received cranial radiotherapy and a longer duration between treatment of their pituitary tumor and start of adult GH replacement therapy. During follow-up, a fracture occurred in 3.8 % (n = 39) of all patients. Compared to patients with previous NFPA, only patients with previous acromegaly had an increased fracture risk after 6 years of GH replacement therapy.

CONCLUSIONS

During GH replacement therapy, an increased fracture risk was observed in severe GHD adult patients previously treated for acromegaly, but not in those previously treated for CD, compared to severe GHD adult patients using GH replacement therapy because of previous NFPA. Further studies are needed to confirm these findings and to elucidate potential underlying mechanisms.

Understanding the effect of acromegaly on the human skeleton

Acromegaly, caused in most cases by Growth Hormone (GH)-secreting pituitary adenomas, is characterized by increased skeletal growth and enlargement of the soft tissue, because GH and its effector Insulin-like Growth factor-1 are important regulators of bone homeostasis and have a central role in the longitudinal bone growth and maintenance of bone mass. Areas covered: Despite the anabolic effect of these hormones is well known, as a result of the stimulation of bone turnover and especially of bone formation, many acromegalic patients are suffering from a form of secondary osteoporosis with increased risk of fractures. Expert commentary: In this review, we summarize the pathophysiology, diagnosis, clinical picture, disease course and management of skeletal complications of acromegaly, focusing in particular on secondary osteoporosis and fracture risk in acromegaly.

Trabecular bone score as a skeletal fragility index in acromegaly patients

SUMMARY

Lumbar spine trabecular bone score (TBS) was significantly decreased in active acromegaly patients. TBS may be useful to assess the skeletal fragility in acromegaly in which bone mineral density (BMD) is not sufficient to represent bone strength and explain the high incidence of fragility fractures in acromegaly patients.

INTRODUCTION

Although the data on BMD are controversial, patients with acromegaly have an increased risk of fragility fracture. We examined the lumbar spine TBS to explain the skeletal deterioration in acromegaly patients.

METHODS

We included 14 men and 19 women acromegaly patients who underwent dual-energy X-ray absorptiometry at the time of diagnosis from 2000 to 2014 at Seoul National University Hospital. Ninety-nine age-, sex- and body mass index-matched controls were recruited. Biochemical parameters, lumbar spine TBS, and BMD at all sites were measured. Gonadal status was evaluated at diagnosis.

RESULTS

Lumbar spine TBS was lower in acromegaly patients than in controls in both genders (1.345 ± 0.121 vs. 1.427 ± 0.087, P = 0.005 in men; 1.356 ± 0.082 vs. 1.431 ± 0.071, P = 0.001 in women). In contrast, BMD at all sites did not differ between the two groups. Hypogonadal acromegaly patients (men, n = 9; women, n = 12) had lower TBS values compared with controls both in men and women (all P < 0.05), although BMD at all sites were similar for the two groups. In eugonadal acromegaly patients, lumbar spine TBS was lower than in women controls only (P = 0.041).

CONCLUSIONS

Skeletal microarchitecture was deteriorated in acromegaly patients as assessed by TBS, which seems to be a consequence of growth hormone excess as well as hypogonadism, especially in women.

Reduction of trabecular and cortical volumetric bone mineral density at the proximal femur in patients with acromegaly

OBJECTIVE

Data on dual energy absorptiometry (DXA)-measured bone mineral density (BMD) at the level of the total hip (TH) and femoral neck (FN) in patients with acromegaly (ACRO) are conflicting. Increase in bone size associated with ACRO may limit the reliability of DXA. Our objective is to evaluate trabecular and cortical volumetric BMD (vBMD) across the proximal femur in ACRO patients.

DESIGN

Cross sectional study in a clinical research center.

PATIENTS

Thirty-five ACRO patients (19 males; mean age, 48±7 years; BMI, 27.5±4.4 kg/m(2); 17 with active disease) and 35 age, gender, and BMI-matched controls.

RESULTS

vBMD was assessed by quantitative computed tomography at the level of the TH, FN, trochanter (TR), and intertrochanteric (IT). Trabecular vBMD was lower in both total and active ACRO as compared with controls (P<0.01). Cortical vBMD was lower in ACRO patients (active and controlled) vs controls at both TH and TR sites (P<0.05). These findings were confirmed when only eugonadal patients were analyzed. Both total cross sectional area (CSA) and average cortical thickness (ACT) were greater in ACRO patients vs controls (P<0.05). An inverse association between disease duration and trabecular vBMD at TH (r=-0.42, P=0.023) and IT (r=-0.41, P=0.026) was also found.

CONCLUSION

Both cortical and trabecular vBMD are reduced at the proximal femur in ACRO patients, regardless of gender, gonadal status, and disease activity. Disease duration is negatively associated with trabecular vBMD at the TH and IT.

Bone and Joint Disorders in Acromegaly

Acromegaly is a chronic, progressive disease caused by a growth hormone (GH)-producing pituitary adenoma, resulting in elevated GH and insulin-like growth factor 1 concentrations. Following appropriate therapy (surgery, radiotherapy and/or medical treatment), many systemic GH-induced comorbid conditions improve considerably. Unfortunately, despite biochemical control, acromegaly patients suffer from a high prevalence of late manifestations of transient GH excess, significantly impairing their quality of life. In this overview article, we summarize the pathophysiology, diagnosis, clinical picture, disease course and management of skeletal complications of acromegaly, focusing on vertebral fractures and arthropathy.

Outcome of complications in acromegaly patients after long-term disease remission

Acromegaly patients suffer from pathologically high growth hormone (GH) and IGF-1 levels that in 99% of cases is due to a GH-producing pituitary adenoma. During active disease, GH excess is associated with a number of pathological conditions, such as hypertension, hypertrophic cardiomyopathy, sleep apnea, arthropathy, vertebral fractures and insulin resistance. After adequate treatment in the form of transsphenoidal surgery, radiotherapy, medical treatment or by a combination of these treatment modalities, several comorbid conditions improve considerably. However, despite long-term biochemical disease control, the prevalence of late manifestations of GH excess is high and significantly impair quality of life. In addition, there is evidence that adequate treatment is not able to normalize mortality risk in these patients. In this review, we critically evaluate the long-term consequences of acromegaly after treatment, focusing on comorbid conditions, quality of life and mortality. We also discuss ongoing challenges in the management of acromegaly patients.

Excessive growth hormone expression in male GH transgenic mice adversely alters bone architecture and mechanical strength

Patients with acromegaly have a higher prevalence of vertebral fractures despite normal bone mineral density (BMD), suggesting that GH overexpression has adverse effects on skeletal architecture and strength. We used giant bovine GH (bGH) transgenic mice to analyze the effects of high serum GH levels on BMD, architecture, and mechanical strength. Five-month-old hemizygous male bGH mice were compared with age- and sex-matched nontransgenic littermates controls (NT; n=16/group). Bone architecture and BMD were analyzed in tibia and lumbar vertebrae using microcomputed tomography. Femora were tested to failure using three-point bending and bone cellular activity determined by bone histomorphometry. bGH transgenic mice displayed significant increases in body weight and bone lengths. bGH tibia showed decreases in trabecular bone volume fraction, thickness, and number compared with NT ones, whereas trabecular pattern factor and structure model index were significantly increased, indicating deterioration in bone structure. Although cortical tissue perimeter was increased in transgenic mice, cortical thickness was reduced. bGH mice showed similar trabecular BMD but reduced trabecular thickness in lumbar vertebra relative to controls. Cortical BMD and thickness were significantly reduced in bGH lumbar vertebra. Mechanical testing of femora confirmed that bGH femora have decreased intrinsic mechanical properties compared with NT ones. Bone turnover is increased in favor of bone resorption in bGH tibia and vertebra compared with controls, and serum PTH levels is also enhanced in bGH mice. These data collectively suggest that high serum GH levels negatively affect bone architecture and quality at multiple skeletal sites.

Bone turnover, bone mineral density, and fracture risk in acromegaly: a meta-analysis

CONTEXT

GH excess causes an increase in bone turnover, but the consequences in terms of skeletal fragility have long been uncertain due to the heterogeneity of studies dealing with this topic.

OBJECTIVE

We conducted a meta-analysis of studies examining the effects of acromegaly on bone turnover, bone mineral density (BMD), and fractures. Furthermore, we evaluated the effects of sex, gonadal status, and activity of disease on skeletal end-points in acromegaly.

DATA SOURCES

We conducted MEDLINE and EMBASE systematic searches up to December 31, 2013.

STUDY ELIGIBILITY CRITERIA

Studies conducted in patients with acromegaly and reporting at least one determinant of skeletal fragility.

DATA EXTRACTION AND ANALYSIS

Study design, patient characteristics, interventions, and outcomes were independently extracted by two authors. We calculated the standardized mean difference (SMD) of bone turnover and BMD differences, whereas fractures were presented as relative frequencies in acromegaly and odds ratios between patients and controls.

RESULTS

Forty-one studies fulfilled eligibility criteria and were therefore selected for data extraction and analysis. A total of 1935 patients were included (eight to 206 per study). Acromegaly patients had higher bone formation (SMD, 1.49; 95% confidence interval [CI], 0.97-2.01; P < .0001) and bone resorption (SMD, 1.57; 95% CI, 1.03-2.10; P < .0001) as compared to control subjects, without significant differences in lumbar spine BMD. BMD at the femoral neck tended to be higher in acromegaly patients vs control subjects (SMD, 0.67; 95% CI, 0.07-1.27; P = .03). Patients with acromegaly had high frequency of vertebral fractures (odds ratio, 8.26; 95% CI, 2.91-23.39; P < .0001), in close relationship with male gender, hypogonadism, and active acromegaly.

LIMITATIONS

LIMITATIONS included heterogeneous study protocols with possible variability in the assessment of skeletal end-points.

CONCLUSIONS

Skeletal fragility is an emerging complication of acromegaly.

Effect of GH/IGF-1 on Bone Metabolism and Osteoporsosis

Background. Growth hormone (GH) and insulin-like growth factor (IGF-1) are fundamental in skeletal growth during puberty and bone health throughout life. GH increases tissue formation by acting directly and indirectly on target cells; IGF-1 is a critical mediator of bone growth. Clinical studies reporting the use of GH and IGF-1 in osteoporosis and fracture healing are outlined. Methods. A Pubmed search revealed 39 clinical studies reporting the effects of GH and IGF-1 administration on bone metabolism in osteopenic and osteoporotic human subjects and on bone healing in operated patients with normal GH secretion. Eighteen clinical studies considered the effect with GH treatment, fourteen studies reported the clinical effects with IGF-1 administration, and seven related to the GH/IGF-1 effect on bone healing. Results. Both GH and IGF-1 administration significantly increased bone resorption and bone formation in the most studies. GH/IGF-1 administration in patients with hip or tibial fractures resulted in increased bone healing, rapid clinical improvements. Some conflicting results were evidenced. Conclusions. GH and IGF-1 therapy has a significant anabolic effect. GH administration for the treatment of osteoporosis and bone fractures may greatly improve clinical outcome. GH interacts with sex steroids in the anabolic process. GH resistance process is considered.

Progression of vertebral fractures despite long-term biochemical control of acromegaly: a prospective follow-up study

BACKGROUND

In active acromegaly, pathologically elevated GH and IGF-1 levels are associated with increased bone turnover and a high bone mass, the latter being sustained after normalization of GH values. In a cross-sectional study design, we have previously reported a high prevalence of vertebral fractures (VFs) of about 60% in patients with controlled acromegaly, despite normal mean bone mineral density (BMD) values. Whether these fractures occur during the active acromegaly phase or after remission is achieved is not known.

OBJECTIVE

Our objective was to study the natural progression of VFs and contributing risk factors in patients with controlled acromegaly over a 2.5-year follow-up period.

METHODS

Forty-nine patients (mean age 61.3 ± 11.1 years, 37% female) with controlled acromegaly for ≥ 2 years after surgery, irradiation, and/or medical therapy and not using bisphosphonates were included in the study. Conventional spine radiographs including vertebrae Th4-L4 were assessed for VFs according to the Genant method. VF progression was defined as development of new/incident fractures and/or a minimum 1-point increase in the Genant scoring of preexisting VFs. BMD was assessed by dual-energy x-ray absorptiometry (Hologic 4500).

RESULTS

Prevalence of baseline VFs was 63%, being highest in men, and fractures were unrelated to baseline BMD. VF progression was documented in 20% of patients, especially in men and in case of ≥ 2 VFs at baseline. VF progression was not related to BMD values or BMD changes over time.

CONCLUSION

Findings from this longitudinal study show that VFs progress in the long term in 20% of patients with biochemically controlled acromegaly in the absence of osteoporosis or osteopenia. These data suggest that an abnormal bone quality persists in these patients after remission, possibly related to pretreatment long-term exposure to high circulating levels of GH.

Acromegaly has a negative influence on trabecular bone, but not on cortical bone, as assessed by high-resolution peripheral quantitative computed tomography

INTRODUCTION

Acromegaly is one of the causes of secondary osteoporosis, although studies of bone mineral density (BMD) have yielded conflicting results and none of them have evaluated the bone properties.

OBJECTIVES AND PATIENTS

Our objective was to correlate, in a cohort of 82 acromegalic patients, BMD and bone microarchitecture, using dual-energy x-ray absorptiometry and high-resolution peripheral quantitative computed tomography, with the presence of type 2 diabetes mellitus (T2DM), disease activity, and gonadal status and to compare these bone parameters between 45 eugonadal acromegalic patients and 45 healthy controls.

RESULTS

Acromegalic patients with T2DM had lower trabecular density and trabecular bone volume to tissue volume ratio in the distal tibia. Patients with active acromegaly exhibited a higher BMD and T-score in the lumbar spine (P = .02 for both) and a higher cortical density in the distal tibia when compared with those with controlled acromegaly (P = .001). After multiple linear regression (including age, presence of T2DM, acromegaly activity, and gonadal status), eugonadism remained the main determinant of bone parameters. The 45 acromegalic patients with eugonadism were compared with 45 age- and sex-matched controls and exhibited lower trabecular densities and impaired microstructures.

CONCLUSIONS

Acromegaly appears to have a deleterious effect on trabecular bone microarchitecture, and in this specific population, the gonadal status might be more important than T2DM or acromegaly activity in determining bone health. High-resolution peripheral quantitative computed tomography seems promising for evaluating acromegalic bone properties and for addressing the limitations posed by dual-energy x-ray absorptiometry.

Vertebral fracture assessment in acromegaly

Most vertebral fractures (VFs) are asymptomatic and incidentally found on X-rays. The effects of acromegaly on bone mineral density (BMD) are still controversial, and the prevalence of VFs in this specific population remains uncertain. The objective of this study was to assess VFs in acromegaly through vertebral fracture assessment (VFA) by dual-energy X-ray absorptiometry (DXA). Seventy-five acromegalic patients from the same center (53 female; age: 48.9±14.5yr) were enrolled in this study. None of them referred previous fragility fracture. They were divided according to the presence or absence of moderate or severe VFs on VFA, a densitometric spine imaging. Age, gender, estimated duration of disease, insulin-like growth factor I levels, disease control and gonadal status, as well as BMD and body composition (analyzed by DXA) were compared between these 2 groups. A prevalence of 10.6% of clinically unapparent VFs was observed. Eight patients had 13 moderate or severe VFs, and only one of them had osteoporosis at densitometry. There was a trend to longer duration of acromegaly before diagnosis, higher prevalence of hypogonadism, and higher BMD Z-score at lumbar spine and femoral neck in fractured patients, without reaching statistical significance. There is a significant prevalence of moderate and severe VFs in acromegalic patients, independently of BMD. More longitudinal and controlled studies are needed to recommend the use of VFA in all acromegalic patients submitted to DXA scan. VFA is simple, practical, uses low radiation, and may provide important information in the management of acromegaly.

Osteoarticular changes in acromegaly

Acromegaly is caused by hypersecretion of growth hormone (GH) and consequently of insulin-like growth factor-I (IGF-1) due to pituitary tumor. Other causes, such as increased growth-hormone releasing hormone (GHRH) production, ectopic GHRH production, and ectopic GH secretion, are rare. Growth hormone and IGF-1 play a role in the regulation of bone metabolism, but accurate effect of growth hormone excess on bone is not fully explained. The issue of osteoarticular manifestations is still very actual, due to development of complications in the majority of patients with acromegaly. Traditionally, acromegaly is considered as a cause of secondary osteoporosis. Nowadays, it is discussed if BMD as predictor of osteoporotic fractures in acromegalic patient is decreased or even normal. Thus, bone quality remains to be more important in assessment of fracture risk. GH excess leads to increased bone turnover, defined by changes of bone markers. The articular manifestations are frequent clinical complications and may be present as the earliest symptom in a significant proportion of acromegalic patients. Articular manifestations are the main causes of morbidity and immobility of these patients, and they are persistent even after successful treatment. Quick recognition of osteoarticular changes and aiming the therapy lead to decrease in complication number.

Influence of diabetes mellitus on vertebral fractures in men with acromegaly

Acromegaly is frequently complicated by fragility vertebral fractures and diabetes mellitus. Since type 2 diabetes mellitus is a cause of secondary osteoporosis in the general population, in this cross-sectional study we aimed at investigating the association between diabetes mellitus and vertebral fractures in males with acromegaly. Fifty-seven patients (median age 47 years, range: 24-85) with active (21 cases) and controlled (36 cases) acromegaly and 57 control subjects were evaluated for bone mineral density (BMD) by DXA and vertebral fractures by a quantitative morphometric analysis. Diabetes mellitus was found in 18 patients and 18 control subjects. The prevalence of vertebral fractures was higher in acromegalic patients as compared with the control subjects (50.9 vs. 10.5%; χ(2): 21.8; P < 0.001). Acromegalic patients with fractures had serum IGF-I values significantly higher (P = 0.009), longer duration of active disease (P < 0.001) and higher prevalence of active acromegaly (P = 0.007) and diabetes mellitus (P = 0.04) as compared to patients who did not fracture. When acromegaly was active, the prevalence of vertebral fractures was high independently of the coexistent diabetes mellitus. On the contrary, when acromegaly was controlled the prevalence of vertebral fractures was significantly higher in patients with diabetes as compared to patients without diabetes (62.6 vs. 28.0%; P = 0.04). In both diabetic and non diabetic patients, vertebral fractures occurred independently of BMD. In conclusion, this study suggests that diabetes mellitus may be associated with an increased prevalence of vertebral fractures in males with acromegaly. However, this effect seems to be relatively attenuated in the presence of persistent GH hypersecretion.

Bone geometry and volumetric bone mineral density in girls with Turner syndrome of different pubertal stages

OBJECTIVE

An increased rate of fractures has been reported in patients with Turner syndrome (TS). We aimed to assess bone geometry and volumetric bone mineral density (vBMD) at the radius in girls with TS and to evaluate the relationships between bone parameters and fracture history.

METHODS AND DESIGN

Sixty-seven girls with TS aged 6-19 years treated currently or in the past with growth hormone (GH) and/or oestrogens were examined using peripheral quantitative computed tomography. Results were compared to reference data.

RESULTS

Cortical area and cortical thickness were low in all age groups (all P<0·001). Height-adjusted total bone area at the diaphysis was increased in prepubertal and postpubertal girls (mean Z-score 1·0, P<0·05 for both) and normal in the pubertal group (mean Z-score 0·1). Cortical vBMD was decreased (mean age-specific Z-scores -2·0, -1·6 and -1·0 for prepubertal, pubertal and postpubertal groups, respectively, P<0·01 for all groups). Height- , age- and cortical thickness-adjusted cortical vBMD was positively correlated to the duration of GH therapy (P=0·012) and to oestrogen administration (P=0·047). Girls with a history of fractures had lower total vBMD at the metaphysis compared to nonfractured TS girls (mean Z-scores -1·7 vs-0·9, P=0·04).

CONCLUSIONS

There is a cortical bone deficit in girls with TS characterized by low cortical area, thin cortex and probably decreased cortical vBMD. Early commencement of GH therapy, as well as oestrogen replacement, is associated with higher cortical vBMD. Further studies should investigate the potential causality of this relation.

Effects of GH-IGF-I excess and gonadal status on bone mineral density and body composition in patients with acromegaly

SUMMARY

Studies on body composition and bone mineral density in acromegaly have conflicting results. Our data point to an increase in lean mass, a decrease in adipose tissue, and that the anabolic effect of GH on bone is partially dependent on modifications in body composition.

INTRODUCTION

The effects of growth hormone (GH) and insulin-like growth factor I (IGF-I) excess and gonadal status on bone mineral density (BMD) and body composition (BC) in acromegalic patients are uncertain.

METHODS

Bone mineral density and BC were evaluated by dual-energy X-ray absorptiometry (Prodigy-GE) in 75 patients (22 men and 53 women) with acromegaly, mean age 48.9 ± 14.5 years. Acromegaly was considered "controlled" when serum IGF-I was within the specific age-adjusted reference range, and serum GH was lower than 2.5 ng/mL. Comparisons between groups were performed using unpaired t test or Mann-Whitney U test. Categorical variables were analyzed by chi-square (x (2)) test. In order to compare data of different subgroups stratified by disease activity and gonadal status, one-way analysis of variance (ANOVA) and Bonferroni post hoc analysis were performed. To evaluate the correlation between GH and IGF-I and densitometric parameters, Pearson and Spearman rank order correlation were performed, as appropriate.

RESULTS

There were no differences in BMD when considering disease activity and gonadal status. Active disease and eugonadism were positively correlated to an increase in lean mass and a decrease in fat mass. After multiple linear regression, there were positive correlations between GH and Z-score at lumbar spine and between lean mass and BMD at proximal femur.

CONCLUSION

Our data support that GH-IGF-I excess and eugonadism have great influence on BC modifications and that the anabolic effects of GH-IGF-I on bone are, at least in part, dependent on these alterations in body composition.

Growth hormone, insulin-like growth factors, and the skeleton

GH and IGF-I are important regulators of bone homeostasis and are central to the achievement of normal longitudinal bone growth and bone mass. Although GH may act directly on skeletal cells, most of its effects are mediated by IGF-I, which is present in the systemic circulation and is synthesized by peripheral tissues. The availability of IGF-I is regulated by IGF binding proteins. IGF-I enhances the differentiated function of the osteoblast and bone formation. Adult GH deficiency causes low bone turnover osteoporosis with high risk of vertebral and nonvertebral fractures, and the low bone mass can be partially reversed by GH replacement. Acromegaly is characterized by high bone turnover, which can lead to bone loss and vertebral fractures, particularly in patients with coexistent hypogonadism. GH and IGF-I secretion are decreased in aging individuals, and abnormalities in the GH/IGF-I axis play a role in the pathogenesis of the osteoporosis of anorexia nervosa and after glucocorticoid exposure.

Effects of insulin-like growth factor binding proteins in bone -- a matter of cell and site

The actions of the insulin-like growth factor (IGF)-system are controlled by six IGF-binding proteins (IGFBPs). The IGFBPs are thought to affect local effects of IGF-I and IGF-II due to higher affinity if compared to IGF-I receptors and due to cell-type specific IGFBP expression patterns. It was found in IGFBP knockout models that the IGFBP family is functionally redundant. Thus, functional analysis of potential effects of IGFBPs is dependent on descriptive studies and models of IGFBP overexposure in vitro and in vivo. In the literature, the role of the IGFBPs for bone growth is highly controversial and, to date, no systematic look has been taken at IGFBPs resolving functional aspects of IGFBPs at levels of cell types and specific locations within bones. Since IGFBPs are thought to represent local modulators of the IGF actions and also exert IGF-independent effects, this approach is particularly reasonable on a physiological level. By sorting the huge number of in part controversial results on IGFBP effects in bone present in the literature for distinct cell types and bone sites it is possible to generate a focused, more specific and a less controversial picture of IGFBP functions in bone.

Increased prevalence of radiological spinal deformities in active acromegaly: a cross-sectional study in postmenopausal women

This cross-sectional study shows that high numbers of postmenopausal women with acromegaly develop vertebral fractures in relation to the activity of disease. In patients with active acromegaly, vertebral fractures occur even in presence of normal BMD, whereas in patients with controlled acromegaly, vertebral fractures are always accompanied by a pathological BMD.

INTRODUCTION

We studied the frequency of radiological vertebral fractures in a cohort of postmenopausal women with active or controlled acromegaly.

MATERIALS AND METHODS

Thirty-six postmenopausal acromegalic patients (15 with active and 21 with controlled disease) were evaluated for BMD, bone metabolism (serum 25-hydroxyvitamin D, PTH, bone-specific alkaline phosphatase [BSALP], and urinary deoxypyridinoline [Dpd]), and vertebral quantitative morphometry. Thirty-six nonacromegalic postmenopausal women, matched for age, were selected among the patients consulting the Bone Center as a control group for BMD evaluation and vertebral quantitative morphometry.

RESULTS

Vertebral fractures were shown in 19 patients (52.8%) and 11 controls (30.6%; chi2: 3.7; p=0.06). Fractured acromegalic women were older and had higher serum IGF-1, Dpd, and BSALP and lower T score and serum vitamin D values compared with nonfractured patients. Moreover, the fractured women had a longer diagnosis and were in the postmenopausal period for a longer period than the nonfractured women. The fracture rate was significantly higher in active than in controlled acromegaly (80% versus 33.3%; chi2: 7.6; p=0.008). The patients with active acromegaly who fractured (12 cases) had significantly higher serum IGF-1 values (356 ng/ml; range: 212-950 versus 120 ng/ml; range: 84-217; p<0.001) and T scores (-1.3 SD, range: -2.9 to +1.3 versus -2.7 SD, range: -3.4 to -1.5, p=0.04) compared with the fractured women whose disease was controlled (7 cases). All fractured women with controlled acromegaly had T scores<-1.0 SD (57.1% of them had osteoporosis, and 42.9% were osteopenic). In contrast, 41.7% of women whose fractures were associated with active disease had a normal T score (>-1.0 SD), whereas osteopenia and osteoporosis were found only in 33.3% and 25.0% of them, respectively.

CONCLUSIONS

This cross-sectional study shows that high numbers of postmenopausal women with acromegaly develop vertebral fractures in relation to the activity of disease. Furthermore, our study shows that, in patients with active acromegaly, vertebral fractures occur even in the presence of normal BMD, whereas in patients with controlled acromegaly, vertebral fractures are always accompanied by a pathological BMD.

Long-term maintenance of the anabolic effects of GH on the skeleton in successfully treated patients with acromegaly

INTRODUCTION

The anabolic actions of growth hormone (GH) are well documented. In acromegaly, the skeletal effects of chronic GH excess have been mainly addressed by evaluating bone mineral density (BMD). Most data were obtained in patients with active acromegaly, and apparently high or normal BMD was observed in the absence of hypogonadism. Data on BMD are not available after successful treatment of acromegaly. Whether the positive effect of GH excess on bone mass is maintained in the long term after clinical and biochemical cure of acromegaly remains to be established.

PATIENTS AND METHODS

In a cross-sectional study design, lumbar spine and femoral neck BMD was measured in 79 acromegalic patients cured or well controlled on octreotide treatment (45 male and 34 female patients; mean age 57+/-1 years). Successful treatment (by surgery, radiotherapy and/or use of octreotide) was defined as normal age-adjusted IGF-I. Mean time after biochemical remission was 10.2+/-7 years.

RESULTS

Normal or increased BMD was observed at the femoral neck and lumbar spine in both men and women in remission after treatment for acromegaly. Similar results were obtained in patients in remission for 5 years or longer. Osteoporosis was present in 15% of the patients, with similar prevalence in men and women. There was no relationship between BMD and duration or severity of GH excess before treatment, gonadal status and presence of pituitary hormone deficiencies. Pituitary irradiation was a strong negative predictor of bone mass at the femoral neck. Long-term bone loss was observed only at the femoral neck.

CONCLUSION

Our data suggest that the anabolic effect of GH on trabecular and cortical bone remains demonstrable after remission of acromegaly, although it may not be maintained at cortical sites in the long term. In the present study, the lack of effect of gonadal status on BMD may be explained by the presence of only mild hypogonadism and by our policy of prompt hormonal replacement therapy for severe hypogonadism. The negative effect of pituitary irradiation on femoral neck BMD remains intriguing, although it is probably related to some degree of the diminished GH secretion frequently observed after this form of treatment.

Bone metabolism in relation to alterations in systemic growth hormone

Growth hormone (GH) has a major role in the maintenance of bone mass in adults by regulating bone remodeling through a complex interaction of circulating GH, insulin-like growth factors (IGFs), IGF binding protein (IGFBPs), and locally produced IGFs and IGFBPs, acting in an autocrine and paracrine way. In vitro data has greatly increased our understanding of GH and IGFs effects and regulation in bone cells under controlled conditions, and especially the molecular pathways involved. However, the GH-and type I IGF-receptor are present in many tissues and various systemic factors may potentially regulate local expression of IGFs and IGFBPs in the intact organism. The use of genetically altered mice has changed this and had a major impact on defining the role of IGFs in skeletal homeostasis, and especially the role of systemic IGF-I in the development and maintenance of the adult skeleton. The focus of this review is to describe recent work on the effect of GH/IGF on remodeling in the adult skeleton emphasizing on data obtained in patient populations (i.e. acromegaly, GH deficiency, postmenopausal osteoporosis) and experimental models (i.e. animals with genetically altered expression of different GH and IGF family members) characterized by different systemic levels of these proteins. The role of IGF-I as a coupling agent between resorption and bone formation through effects on osteoprotegerin (OPG) and receptor activator of NFkappaB ligand (RANKL) are also discussed.

Longitudinal in vivo effects of growth hormone overexpression on bone in transgenic mice

In this study we examined the effect of systemic overexpression of GH on bone in transgenic mice longitudinally in vivo over a period of 9 months. We observed substantially increased BMC in GH transgenic mice and a significant reduction in serum osteocalcin. GH effects on bone were strongly dependent on gender and developmental stage.

INTRODUCTION

State-of-the-art bone marker and microimaging technology was applied in this longitudinal study to examine bone metabolism, BMC, bone density, and cortical bone structure over the life span of growth hormone (GH) transgenic (tg) mice.

MATERIALS AND METHODS

Thirty-eight mice from four genetic groups (male, female, tg, and controls) were examined with DXA, and their femur and tibia were examined with peripheral QCT (pQCT). Osteocalcin (formation) and collagen cross-links (resorption) from serum and urine were also measured at postnatal weeks 3, 6, 9, 12, 18, 26, and 38.

RESULTS

GH tg mice displayed a significant increase in body weight (up to 50%) and BMC (up to 90%), but serum osteocalcin was significantly reduced compared with controls. GH tg females (but not males) displayed increased trabecular density over controls up to week 12. In contrast, male (but not female) GH tg mice displayed a higher cortical cross-sectional area than controls. Cortical density was significantly lower in both male and female GH tg mice compared with control mice.

CONCLUSIONS

The increase in BMC in GH tg mice is associated with reduced serum osteocalcin levels, indicating that bone turnover may be lower than in the control mice. On a structural level, bone responds to GH excess in a gender-specific manner, with alterations varying substantially between different developmental stages.

Growth hormone substitution increases gene expression of members of the IGF family in cortical bone from women with adult onset growth hormone deficiency--relationship with bone turn-over

OBJECTIVE

To investigate the effects of growth hormone (GH) replacement therapy on bone matrix gene expression of insulin-like growth factors (IGFs) and markers of bone metabolism in women with adult-onset GH deficiency (GHD).

DESIGN AND METHODS

Nineteen women, mean age 45 (range 24-56) years, were included in a double-blind, placebo-controlled parallel group study for 12 months. Biochemical markers were measured at baseline, 6 and 12 months. Bone biopsies were obtained and BMD was measured at baseline and after 12 months.

RESULTS

Maximum responses were observed after 6 and 12 months, for bone resorptive and bone formative markers respectively. GH therapy enhanced gene expression in cortical bone of IGFs, GH-and calcitonin-receptor (CR) and osteoprotegerin (OPG), however with the most pronounced effects on CR and IGF-I. Changes in IGF-I gene expression during longitudinal follow-up were significantly correlated with changes in both circulating IGF-I (r = 0.82, p < 0.05), changes in markers of enhanced osteoclastic activity, measured both locally in bone (CR, r = 0.87, p < 0.01) and in serum (CTX-I, r = 0.86, p < 0.05), as well as serum bone ALP (r = 0.96, p < 0.01).

CONCLUSIONS

This study indicates that both liver- and bone-derived IGF-I may be significant in mediating the effects of GH on bone metabolism in humans.