Persistent Deficits in Bone Quality in Treated Acromegaly: Evidence From Assessments of Microstructure

New insights into the vitamin D/PTH axis in endocrine-driven metabolic bone diseases

BACKGROUND

Endocrine regulation of bone metabolisms is the focus of the "Skeletal Endocrinology" series of meetings.

AIMS

To report on the outcome of the discussion on the role of vitamin D/PTH axis in endocrine osteopathies held during the 10th Skeletal Endocrinology Meeting which took place in Stresa (Italy) in March 2023.

OUTCOMES

Vitamin D/PTH axis has relevant influence on several outcomes in the general population and in patients affected by endocrinopathies such as hypoparathyroidism and secreting pituitary adenomas.

CONCLUSIONS

Assessing the status of the vitamin D/PTH axis and using vitamin D and PTH as therapeutic agents is mandatory in several endocrine-related bone metabolic conditions.

The direct impact of pegvisomant on osteoblast functions and bone development

PURPOSE

Acromegaly is a chronic disease characterized by growth hormone (GH) hypersecretion, usually caused by a pituitary adenoma, resulting in elevated circulating levels of insulin-like growth factor type I (IGF-I). Pegvisomant (PEG), the GH-receptor (GHR) antagonist, is used in treating acromegaly to normalize IGF-I hypersecretion. Exposure to increased levels of GH and IGF-I can cause profound alterations in bone structure that are not completely reverted by treatment of GH hypersecretion. Indeed, there is evidence that drugs used for the treatment of acromegaly might induce direct effects on skeletal health regardless of biochemical control of acromegaly.

METHODS

We investigated, for the first time, the effect of PEG on cell proliferation, differentiation, and mineralization in the osteoblast cell lines MC3T3-E1 and hFOB 1.19 and its potential impact on bone development in zebrafish larvae.

RESULTS

We observed that PEG did not affect osteoblast proliferation, apoptosis, alkaline phosphatase (ALP) activity, and mineralization. After PEG treatment, the analysis of genes related to osteoblast differentiation showed no difference in Alp, Runx2, or Opg mRNA levels in MC3T3-E1 cells. GH significantly decreased cell apoptosis (- 30 ± 11%, p < 0.001) and increased STAT3 phosphorylation; these effects were suppressed by the addition of PEG in MC3T3-E1 cells. GH and PEG did not affect Igf-I, Igfbp2, and Igfbp4 mRNA levels in MC3T3-E1 cells. Finally, PEG did not affect bone development in zebrafish larvae at 5 days post-fertilization.

CONCLUSION

This study provides a first evidence of the impact of PEG on osteoblast functions both in vitro and in vivo. These findings may have clinically relevant implications for the management of skeletal health in subjects with acromegaly.

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.