Understanding the effect of acromegaly on the human skeleton

GH receptor polymorphisms guide second-line therapies to prevent acromegaly skeletal fragility: preliminary results of a pilot study

Background

Skeletal fragility is characterized by increased frequency of vertebral fractures (VFs) in acromegaly. Several trials were conducted to identify modifiable risk factors and predictors of VFs, with limited data on the prognostic role of GH receptor (GHR) isoforms. In this study, we investigated the potential role of GHR polymorphism on the occurrence of incidental VFs (i-VFs), in patients treated with second-line medical therapies.

Methods

A longitudinal, retrospective, observational study was conducted on a cohort of 45 acromegalic patients not-responsive to first-generation somatostatin receptor ligands (fg-SRLs) and treated with GHR antagonist (Pegvisomant) or with the second-generation SRLs (Pasireotide long-acting release).

Results

Second line treatments were Pegvisomant plus fg-SRLs in 26 patients and Pasireotide LAR in 19 patients. From the group treated with fg-SRLs+Peg-V, the fl-GHR isoform was identified in 18 patients (69.2%) and the d3-GHR isoform in 8 patients (30.8%). I-VFs arose exclusively in fl-GHR isoform carriers (p=0.039). From the group treated with Pasireotide LAR, the fl-GHR isoform was identified in 11 patients (57.9%), and the d3-GHR isoform in 8 patients (42.1%). I-VFs arose exclusively in d3-GHR isoform carriers (p=0.018). Patients with fl-GHR isoform had a higher risk for i-VFs if treated with fg-SRL+Peg-V (OR: 1.6 95%IC: 1.1-2.3, p=0.04), and a lower risk if treated with Pasi-LAR (OR: 0.26 IC95%: 0.11-0.66, p=0.038).

Conclusions

Our data support a predictive role of the GHR isoforms for the occurrence of i-VFs in acromegalic patients treated with second-line drugs, tailored to the individual patient. The knowledge of the GHR polymorphism may facilitate the choice of second-line therapies, improving the therapeutic approach, in the context of personalized medicine.

Skeletal complications in acromegaly

Hypersecretion of growth hormone (GH) is rare and typically results from a pituitary functional tumor - somatotropinoma. It leads to excessive linear bone growth and manifests as gigantism if occurring in childhood and adolescence, before the closure of epiphyses or as a acromegaly in adulthood. The excess of GH impacts bone metabolism directly as well as indirectly through increased insulin-like growth factor 1 (IGF-1). In acromegaly as a consequence of overproduction of GH and IFG-1 and the influence of these hormones on bone osteoblasts, bone metabolism, growth and density increase. However, bone turnover is accelerated causing impaired bone microstructure and strength, which may lead to increased risk of vertebral fractures irrespective of normal bone mineral density. Apart from the changes in bone architecture, acromegaly also results in a degenerative joint disease of a different nature than primary osteoarthritis. Moreover, acromegaly leads to cardiovascular, metabolic and respiratory complications, and thus significantly impairs the quality of life. In this review, authors summarize the pathophysiology, diagnosis, and treatment of bone and joint disease in acromegaly.

Impact of the diagnostic delay of acromegaly on bone health: data from a real life and long term follow-up experience

INTRODUCTION

Acromegaly is a chronic disease with systemic complications. Disease onset is insidious and consequently typically burdened by diagnostic delay. A longer diagnostic delay induces more frequently cardiovascular, respiratory, metabolic, neuropsychiatric and musculoskeletal comorbidities. No data are available on the effect of diagnostic delay on skeletal fragility. We aimed to evaluate the effect of diagnostic delay on the frequency of incident and prevalent of vertebral fractures (i-VFs and p-VFs) in a large cohort of acromegaly patients.

PATIENTS AND METHODS

A longitudinal, retrospective and multicenter study was conducted on 172 acromegaly patients.

RESULTS

Median diagnostic delay and duration of follow-up were respectively 10 years (IQR: 6) and 10 years (IQR: 8). P-VFs were observed in 18.6% and i-VFs occurred in 34.3% of patients. The median estimated diagnostic delay was longer in patients with i-VFs (median: 11 years, IQR: 3), in comparison to those without i-VFs (median: 8 years, IQR: 7; p = 0.02). Age at acromegaly diagnosis and at last follow-up were higher in patients with i-VFs, with respect to those without i-VFs. The age at acromegaly diagnosis was positively associated with the diagnostic delay (p < 0.001, r = 0.216). A longer history of active acromegaly was associated with a high frequency of i-VFs (p = 0.03). The logistic regression confirmed that patients with a diagnostic delay > 10 years had 1.5-folds increased risk of developing i-VFs (OR: 1.5; 95%CI: 1.1-2; p = 0.017).

CONCLUSION

Our data showed that the diagnostic delay in acromegaly has a significant impact on VF risk, further supporting the clinical relevance of an early acromegaly diagnosis.

Acromegaly is associated with vertebral deformations but not vertebral fractures: Results of a cross-sectional monocentric study

OBJECTIVES

Patients with acromegaly appear to be at increased risk of vertebral fractures despite normal bone mineral density. We investigated the prevalence of vertebral fractures in a cohort of acromegalic patients under 80 years of age.

METHODS

Monocentric cross-sectional study performed at Nantes University Hospital from 1988 to 2018. Fifty patients (18 females, 32 males) with a median age of 52.3 years (range: 27-78) were included. Radiological vertebral fractures were evaluated on conventional lumbar and thoracic spine radiographs using Genant's semiquantitative fracture assessment. We studied qualitative abnormalities of the spine using three criteria: osteophytes, disc-space narrowing and wedge-shaped vertebrae. We analysed bone mineral density and endocrine status.

RESULTS

Three patients (6%) had a vertebral fracture: one grade 1 and two grade 2 according to Genant's assessment, with two osteoporotic and one osteopenic patients. They had no unsubstituted pituitary deficiency. Considering the frank deformations (osteophyte or disc narrowing≥grade 2 or wedge-shaped), the thoracic spine was deformed in 22 patients (44%) and the lumbar spine in 21 patients (42%).

CONCLUSION

Acromegalic patients had a low prevalence of vertebral fractures but had a significant amount of vertebral deformations. We speculate that this high prevalence of frank deformations could explain the previously reported high prevalence of vertebral fractures.

Increased Serum Sclerostin Levels in Patients With Active Acromegaly

CONTEXT

Bone mineral density is normal in acromegalic patients and the cause of increased fracture risk that characterizes active acromegaly is unknown.

OBJECTIVE

This study compared serum sclerostin levels between patients with active acromegaly and healthy individuals.

DESIGN, SETTING, AND PARTICIPANTS

The serum sclerostin levels of patients with active acromegaly were compared with those of healthy volunteers in a cross-sectional study. The mean age of the 30 acromegaly patients (male/female: 14/16) was 47.26 ± 12.52 years (range, 18-64 years) and that of the healthy volunteers (male/female: 17/13) was 44.56 ± 10.74 years (range, 19-62 years). IGF-1 and GH levels were measured using an electrochemiluminescence method, and serum sclerostin levels using an ELISA. The Mann-Whitney U test was used to compare sclerostin levels between the 2 groups. The correlations of sclerostin level with IGF-1 and GH were determined using Spearman's test.

RESULTS

The 2 groups did not differ in age or sex (P > 0.05). The median GH and IGF-1 levels in the patient group were 2.49 ng/mL (range, 0.22-70.00 ng/mL) (interquartile range [IQR], 1.3-4.52) and 338.5 ng/mL (range, 147-911 ng/mL) (IQR, 250-426), respectively. The median GH and IGF-1 levels in the control group were 0.95 ng/mL (range, 0.3-2.3) and 144 ng/mL (range, 98-198), respectively. The median sclerostin level was 29.95 ng/mL (range, 7.5-78.1 ng/mL) (IQR, 14.37-37.47) in the acromegaly group and 22.44 ng/mL (range, 8.45-36.44 ng/mL) (IQR, 13.71-27.52) in the control group (P < 0.05). There was a moderate positive correlation between the sclerostin and IGF-1 levels (rho = 0.54; P < 0.01), and between the sclerostin and GH levels (rho = 0.41; P < 0.05).

CONCLUSIONS

High sclerostin levels may contribute to the increased fracture risk seen in patients with acromegaly.

Effects of Pegvisomant and Pasireotide LAR on Vertebral Fractures in Acromegaly Resistant to First-generation SRLs

PURPOSE

Osteopathy is an emerging complication of acromegaly. In somatostatin receptor ligands (SRL)-resistant patients, pegvisomant (PegV) and pasireotide LAR (Pasi) are used for acromegaly treatment, but their effect on skeletal health is still not defined.

METHODS

In a longitudinal retrospective international study, we evaluated incidence of radiological vertebral fractures (VFs) in 55 patients with acromegaly resistant to first-generation SRL.

RESULTS

At study entry, prevalent VFs occurred in 23 patients (41.8%). Biochemical acromegaly control was reached in 66.7% of patients on PegV and in 66.7% of patients on Pasi. During the follow-up, incident VFs (iVFs) were detected in 16 patients (29.1%). Occurrence of iVFs was associated with prevalent VFs (P = .002), persistence of active acromegaly (P = .01) and higher value of insulin-like growth factor 1 (IGF-1) during follow-up (P = .03). Among patients with active disease at last visit, iVFs occurred less frequently in patients on treatment with Pasi (25%) compared to PegV (77.8% P = .04), independently of the IGF-1 values (P = .90). In patients who reached biochemical control, 22.7% on PegV and 12.5% on Pasi had iVFs (P = .40). Among both treatment groups, the presence of pre-existent VFs was the main determinant for iVFs.

CONCLUSION

Our data show for the first time that patients with biochemically active disease treated with Pasi had lower risk of iVFs versus those treated with PegV. It also confirms that the presence of pre-existent VFs was the main determinant for iVFs. Additional studies on larger populations and with longer follow-up are needed to confirm our data and disclose the mechanisms underlying our findings.

Exon 3-deleted growth hormone receptor isoform is not related to worse bone mineral density or microarchitecture or to increased fracture risk in acromegaly

PURPOSE

Acromegaly is a cause of secondary osteoporosis and is associated with increased risk of vertebral fractures (VFs). The influence of exon 3-deleted isoform of growth hormone receptor (d3-GHR) on bone microarchitecture has not been studied in acromegaly.

AIM

The aim of this study was to analyze the associations between d3-GHR isoform and bone mineral density (BMD), bone microarchitecture, and VFs in acromegaly patients.

METHODS

Consecutive acromegaly patients treated at a single reference center were included. BMD was analyzed using dual-energy X-ray absorptiometry (DXA) and bone microarchitecture was analyzed by high-resolution peripheral quantitative computed tomography (HR-pQCT). The presence of moderate to severe VFs was assessed by thoracic and lumbar X-ray. GHR genotyping was analyzed by PCR, and full-length isoform of GHR (fl-GHR) was represented by a 935-bp fragment and d3-GHR by a 532-bp fragment.

RESULTS

Eighty-nine patients were included [56 females; median age at diagnosis: 43 years (17-78)]. Disease was uncontrolled in 63% of patients. At least one d3-GHR allele was present in 60% of patients. Frequency of active disease (p = 0.276) and hypogonadism (p = 1.000) was not different between patients with fl-GHR and those with at least one d3-GHR. There was no difference in any DXA or HR-pQCT parameters between patients with fl-GHR and those with d3-GHR. Significant VFs were observed in 14% of patients, but there was no difference in frequency between patients with fl-GHR and those with at least one d3-GHR allele (p = 0.578).

CONCLUSIONS

Presence of d3-GHR was not associated with worse BMD or bone microarchitecture or with higher frequency of significant VFs.

Italian Association of Clinical Endocrinologists (AME) and Italian AACE Chapter Position Statement for Clinical Practice: Acromegaly - Part 1: Diagnostic and Clinical Issues

Acromegaly is a rare disease. Improvements in lifespan in these patients have recently been reported due to transsphenoidal surgery (TSS), advances in medical therapy, and strict criteria for defining disease remission. This document reports the opinions of a group of Italian experts who have gathered together their prolonged clinical experience in the diagnostic and therapeutic challenges of acromegaly patients. Both GH and IGF-I (only IGF-I in those treated with Pegvisomant) are needed in the diagnosis and follow-up. Comorbidities (cardio-cerebrovascular disease, sleep apnea, metabolic derangement, neoplasms, and bone/joint disease) should be specifically addressed. Any newly diagnosed patient should be referred to a multidisciplinary team experienced in the treatment of pituitary adenomas.

Prevalence of morphometric vertebral fractures in "difficult" patients with acromegaly with different biochemical outcomes after multimodal treatment

INTRODUCTION

Skeletal fragility with high risk of vertebral fractures is an emerging complication of acromegaly in close relationship with duration of active disease. The aim of this cross-sectional study was to evaluate the prevalence and determinants of vertebral fractures in males and females with a history of long-standing active acromegaly undergoing treatment with Pegvisomant.

SUBJECTS AND METHODS

Thirty-eight patients (25 females, 13 males) with acromegaly under Pegvisomant therapy were evaluated for vertebral fractures and bone mineral density at lumbar spine and femoral neck. Gonadal status, serum IGF1 levels and growth hormone receptor genotype were also assessed.

RESULTS

Vertebral fractures were detected in 12 patients (31.6%). Fractured patients had longer duration of active disease (p = 0.01) with higher frequency of active acromegaly (p = 0.04), received higher dose of Pegvisomant (p = 0.008), and were more frequently hypogonadic (p = 0.02) as compared to patients who did not fracture. Stratifying the patients for gender, vertebral fractures were significantly associated with Pegvisomant dose (p = 0.02) and untreated hypogonadism (p = 0.02) in males and with activity of disease (p = 0.03), serum insulin-like growth factor-I values (p = 0.01) and d3GHR polymorphism (p = 0.005) in females. No significant association was found between vertebral fractures and bone mineral density at either skeletal site.

CONCLUSION

Vertebral fractures are a frequent complication of long-standing active acromegaly. When patients are treated with Pegvisomant, vertebral fractures may occur in close relationship with active acromegaly and coexistent untreated hypogonadism.