Bone microarchitecture impairment in prolactinoma patients assessed by HR-pQCT

Modern approach to bone comorbidity in prolactinoma

Prolactinomas account for more than half of pituitary adenomas, and besides their clinical impact on fertility and gonadal function, they lead to detrimental effects on bone. Patients with prolactinoma are prone to deterioration of bone structure caused not only by prolactin (PRL) induced hypogonadism but also by its direct actions on bone cells and calcium metabolism. However, clinical studies have shown inconsistent evidence regarding whether PRL could have a deleterious effect independently from gonadal insufficiency on skeletal integrity. Seminal studies from our group reported an increased prevalence of vertebral fractures (VFs) in both female and male patients with prolactinoma. Treatment of prolactinoma with dopamine agonists can restore gonadal function and improve bone mineral density. Since the presence of VFs may be related to more aggressive disease, bone comorbidities in prolactinoma should be managed by a multidisciplinary team in line with the recent concept of 'pituitary tumors centers of excellence'. The review aims to evaluate the mechanism of PRL actions on bone, as well as to provide practical indications for a modern approach to the management of skeletal complications of patients with prolactin-secreting adenoma considering different clinical characteristics and outcomes.

Skeletal fragility in pituitary disease: how can we predict fracture risk?

Pituitary hormones play a crucial role in regulating skeletal physiology, and skeletal fragility is a frequent complication of pituitary diseases. The ability to predict the risk of fracture events is crucial for guiding therapeutic decisions; however, in patients with pituitary diseases, fracture risk estimation is particularly challenging. Compared to primary osteoporosis, the evaluation of bone mineral density by dual X-ray absorptiometry is much less informative about fracture risk. Moreover, the reliability of standard fracture risk calculators does not have strong validations in this setting. Morphometric vertebral assessment is currently the cornerstone in the assessment of skeletal fragility in patients with pituitary diseases, as prevalent fractures remain the strongest predictor of future fracture events. In recent years, new tools for evaluating bone quality have shown promising results in assessing bone impairment in patients with pituitary diseases, but most available data are cross-sectional, and evidence regarding the prediction of incident fractures is still scarce. Of note, apart from measures of bone density and bone quality, the estimation of fracture risk in the context of pituitary hyperfunction or hypofunction cannot ignore the evaluation of factors related to the underlying disease, such as its severity and duration, as well as the specific therapies implemented for its treatment. Aim of this review is to provide an up-to-date overview of all major evidence regarding fracture risk prediction in patients with pituitary disease, highlighting the need for a tailored approach that critically integrates all clinical, biochemical, and instrumental data according to the specificities of each disease.

Vitamin D in pituitary driven osteopathies

The evidence that pituitary hormones may bypass peripheral endocrine glands to exert remarkable effects on the skeleton is gaining ground. Both hormonal excess and deficit may determine impairment in bone structure, and they commonly result in bone loss in patients affected by pituitary and neuroendocrine disorders. Vertebral fractures are the most common skeletal alterations and may occur independently of bone mass. Use of vitamin D (VD) supplementation is still debated in this setting. This review will focus on the interactions between different metabolites of VD and pituitary hormones, and the effects of VD supplementation on bone metabolism in patients with pituitary diseases.

Impact of medical therapy for hormone-secreting Pituitary tumors on bone

PURPOSE

Bone health is often impaired in patients with hormone-secreting pituitary tumors. Since medical therapy is central to their care, understanding how its use impacts on this is highly important.

METHODS

This review summarizes a systemmatic review of the literature on the effects of medical therapies for hormone-secreting pituitary tumors on bone.

RESULTS

In acromegaly, medical therapy lowers bone turnover marker (BTM) levels, consistent with correction of the high bone turnover of active disease, and overall, areal bone mineral density (aBMD) does not change or increases. Somatostatin-receptor ligand (SRL) and pegvisomant-treated acromegaly patients have persistently reduced volumetric BMD and microarchitectural abnormalities of the peripheral skeleton, deficits that are similar to those in surgically-treated patients. Fracture risk remains elevated in medically-treated acromegaly patients but in conjunction with biochemical control the risk is lessened. Treatment of prolactin-secreting tumors with dopamine agonists is associated with improvements in aBMD, but this does not always fully normalize despite effective medical treatment of the prolactinoma. In one cross-sectional study, prolactinoma patients had lower total volumetric BMD and impaired microarchitecture suggesting that bone microstructure does not fully normalize despite dopamine agonist therapy. Cross-sectional studies show a high rate of VF in patients with prolactin-secreting tumors that is lowered on cabergoline therapy, but still the fracture rate of men and postmenopausal women is higher than that of controls in some studies. Studies on the effects of modern-day medical therapy for Cushing's disease on bone are lacking.

CONCLUSION

More research is needed on the effectsof medical therapies for hormone secreting pituitary tumors on bone health.

Hyperprolactinemia Due to Prolactinoma has an Adverse Impact on Bone Health with Predominant Impact on Trabecular Bone: A Systematic Review and Meta-Analysis

BACKGROUND

No meta-analysis has holistically analysed and summarized the effect of prolactin excess due to prolactinomas on bone mineral metabolism. We undertook this meta-analysis to address this knowledge-gap.

METHODS

Electronic databases were searched for studies having patients with hyperprolactinemia due to prolactinoma and the other being a matched control group. The primary outcome was to evaluate the differences in BMD Z-scores at different sites. The secondary outcomes of this study were to evaluate the alterations in bone mineral density, bone mineral content and the occurrence of fragility fractures.

RESULTS

Data from 4 studies involving 437 individuals was analysed to find out the impact of prolactinoma on bone mineral metabolism. Individuals with prolactinoma had significantly lower Z scores at the lumbar spine [MD -1.08 (95 % CI: -1.57 - -0.59); P < 0.0001; I2 = 54 % (moderate heterogeneity)] but not at the femur neck [MD -1.31 (95 % CI: -3.07 - 0.45); P = 0.15; I2 = 98 % (high heterogeneity)] as compared to controls. Trabecular thickness of the radius [MD -0.01 (95 % CI: -0.02 - -0.00); P = 0.0006], tibia [MD -0.01 (95 % CI: -0.02 - -0.00); P=0.03] and cortical thickness of the radius [MD -0.01 (95 % CI: -0.19 - -0.00); P = 0.04] was significantly lower in patients with prolactinoma as compared to controls. The occurrence of fractures was significantly higher in patients with prolactinoma as compared to controls [OR 3.21 (95 % CI: 1.64 - 6.26); P = 0.0006] Conclusion: Bone mass is adversely affected in patients with hyperprolactinemia due to prolactinoma with predominant effects on the trabecular bone.

New tools for bone health assessment in secreting pituitary adenomas

Pituitary hormones regulate skeletal physiology, and excess levels affect bone remodeling and alter bone microstructure. Vertebral fractures (VFs) are an early phenomenon of impaired bone health in secreting pituitary adenomas. However, they are not accurately predicted by areal bone mineral density (BMD). Emerging data demonstrate that a morphometric approach is essential for evaluating bone health in this clinical setting and is considered to be the gold standard method in acromegaly. Several novel tools have been proposed as alternative or additional methods for the prediction of fractures, particularly in pituitary-driven osteopathies. This review highlights the novel potential biomarkers and diagnostic methods for bone fragility, including their pathophysiological, clinical, radiological, and therapeutic implications in acromegaly, prolactinomas, and Cushing's disease.