Inhibition of growth hormone receptor activation by pegvisomant may increase bone density in acromegaly

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.

Pegvisomant in acromegaly: an update

BACKGROUND

In 2007, we published an opinion document to review the role of pegvisomant (PEG) in the treatment of acromegaly. Since then, new evidence emerged on the biochemical and clinical effects of PEG and on its long-term efficacy and safety.

AIM

We here reviewed the emerging aspects of the use of PEG in clinical practice in the light of the most recent literature.

RESULTS

The clinical use of PEG is still suboptimal, considering that it remains the most powerful tool to control IGF-I in acromegaly allowing to obtain, with a pharmacological treatment, the most important clinical effects in terms of signs and symptoms, quality of life and comorbidities. The number of patients with acromegaly exposed to PEG worldwide has become quite elevated and the prolonged follow-up allows now to deal quite satisfactorily with many clinical issues including major safety issues, such as the concerns about possible tumour (re)growth under PEG. The positive or neutral impact of PEG on glucose metabolism has been highlighted, and the clinical experience, although limited, with sleep apnoea and pregnancy has been reviewed. Finally, the current concept of somatostatin receptor ligands (SRL) resistance has been addressed, in order to better define the acromegaly patients to whom the PEG option may be offered.

CONCLUSIONS

PEG increasingly appears to be an effective and safe medical option for many patients not controlled by SRL but its use still needs to be optimized.

Rapid decline in bone turnover markers but not bone mineral density in acromegalic patients after transsphenoidal surgery

Growth hormone (GH) and insulin-like growth factor-I (IGF-I) play important roles in maintaining bone metabolism and bone mineral density (BMD) in adulthood, in addition to stimulating longitudinal bone growth in childhood. However, information on the effect of GH excess on bone metabolism and BMD is incomplete and requires further analysis. The aim of this study is to clarify the effect of rapid decline in GH levels after transsphenoidal surgery (TSS) on bone metabolism in acromegalic patients. In this prospective study, 22 patients (11 males and 11 females) with active acromegaly underwent TSS. Bone formation marker (serum bone alkaline phosphatase: BAP), bone resorption marker (urinary type I collagen cross-linked N-telopeptide: urinary NTx) and BMD were measured before and at 3 and 12 months after TSS. BAP was significantly decreased at 12 months after TSS, but not at 3 months. Urinary NTx was significantly decreased at 3 and 12 months after TSS. BMD did not change after TSS. In conclusion, the rapid fall in GH level after TSS had no effect on BMD for up to 12 months after TSS despite the decrease in markers of bone formation and resorption.

Medical therapy of acromegaly

This paper outlines the present status of medical therapy of acromegaly. Indications for permanent postoperative treatment, postirradiation treamtent to bridge the interval until remission as well as primary medical therapy are elaborated. Therapeutic efficacy of the different available drugs-somatostatin receptor ligands (SRLs), dopamine agonists, and the GH antagonist Pegvisomant-is discussed, as are the indications for and efficacy of their respective combinations. Information on their mechanism of action, and some pharmakokinetic data are included. Special emphasis is given to the difficulties to define remission criteria of acromegaly due to technical assay problems. An algorithm for medical therapy in acromegaly is provided.