Prevalence of vertebral fractures and serum sclerostin levels in acromegaly

High prevalence of morphometric vertebral fractures opportunistically detected on thoracic radiograms in patients with non-functioning pituitary adenoma

PURPOSE

Vertebral fractures (VFs), the hallmark of skeletal fragility, have been reported as an emerging complication in patients with pituitary diseases associated with hormonal excess and/or deficiency, independently from bone mineral density. Non-functioning pituitary adenoma (NFPA) is amongst the most frequent pituitary adenomas; however, skeletal health in this context has never been investigated. We aimed at assessing the prevalence and the determinants of morphometric VFs in patients with NFPA.

METHODS

We enrolled 156 patients (79 M/77F, mean age 55.75 ± 12.94 years) at admission in Neurosurgery Unit before trans-sphenoidal surgery and compared them with an age and sex-matched control group of subjects with neither history/risk factors for secondary osteoporosis nor pituitary disorders. We performed a vertebral morphometric evaluation of the thoracic spine on pre-operative X-ray images (MTRx) and collected biochemical, demographic, and clinical data from the entire cohort.

RESULTS

The prevalence of thoracic VFs in patients with NFPA was significantly higher than the control group (26.3% vs. 10.3%; p < 0.001). In the NFPA group, 20 patients (48.8% of the fractured patients) showed multiple VFs, 14 (34.1% of them) showed moderate/severe VFs. Patients with VFs were significantly older and had lower serum free triiodothyronine (fT3) levels than non-fractured ones (p = 0.002 and p = 0.004; respectively). The prevalence of secondary male hypogonadism was higher among men with VFs as compared to those with no VFs (72% vs. 48.1%; p = 0.047). Consistently, total testosterone levels in males were significantly lower in fractured patients than in non-fractured ones (p = 0.02). The prevalence of gonadotroph adenomas was significantly higher among patients with VFs (p = 0.02). In multiple logistic regression analysis, older age and lower serum fT3 levels were independent factors predicting the risk for VFs.

CONCLUSIONS

For the first time, we reported a high prevalence of thoracic radiological VFs in patients with NFPAs. Our data should prompt clinicians to proceed with a clinical bone fragility evaluation already during the diagnostic work-up, particularly in those with concomitant hypogonadism, or in those with older age and/or with lower fT3.

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.

Diagnosis and therapeutic approach to bone health in patients with hypopituitarism

The results of many studies in recent years indicate a significant impact of pituitary function on bone health. The proper function of the pituitary gland has a significant impact on the growth of the skeleton and the appearance of sexual dimorphism. It is also responsible for achieving peak bone mass, which protects against the development of osteoporosis and fractures later in life. It is also liable for the proper remodeling of the skeleton, which is a physiological mechanism managing the proper mechanical resistance of bones and the possibility of its regeneration after injuries. Pituitary diseases causing hypofunction and deficiency of tropic hormones, and thus deficiency of key hormones of effector organs, have a negative impact on the skeleton, resulting in reduced bone mass and susceptibility to pathological fractures. The early appearance of pituitary dysfunction, i.e. in the pre-pubertal period, is responsible for failure to achieve peak bone mass, and thus the risk of developing osteoporosis in later years. This argues for the need for a thorough assessment of patients with hypopituitarism, not only in terms of metabolic disorders, but also in terms of bone disorders. Early and properly performed treatment may prevent patients from developing the bone complications that are so common in this pathology. The aim of this review is to discuss the physiological, pathophysiological, and clinical insights of bone involvement in pituitary disease.

Acromegaly versus hypogonadism: Bone fragility and evaluation

INTRODUCTION

Osteopathy in patients with acromegaly is characterized by increased prevalence of vertebral fragility fractures (VF). However, the diagnostic criteria for osteoporosis are seldomly met in terms of bone mineral density (BMD), as patients with acromegaly frequently present normal BMD for age and gender.

METHODOLOGY

We performed a cross-sectional study on 71 patients with acromegaly and 75 patients with hypogonadism. Turnover markers comprised alkaline phosphatase, osteocalcin, the C-terminal telopeptide of type I collagen and total procollagen type-1 amino-terminal propeptide; imaging comprised dual x-ray absorptiometry for BMD, T and Z scores of the lumbar spine, femoral neck and total hip, trabecular bone score (TBS), and x-ray scans of the thoracic and lumbar spine.

RESULTS

Vertebral fractures (VF) in subjects with acromegaly were significantly more frequent than in subjects with hypogonadism, with a prevalence of 29.6% compared to 9.3%. Patients with acromegaly had significantly higher BMD at all skeletal sites but lower TBS than hypogonadal subjects. This difference remained statistically significant after grouping patients with acromegaly according to gonadal status and comparing them with patients with hypogonadism. However, presence of hypogonadism in patients with acromegaly did not influence BMD, TBS or VF prevalence. Moreover, patients with active acromegaly did not have significantly different BMD, TBS and VF prevalence compared to patients with controlled disease. Patients with acromegaly with VF had significantly lower BMD at all skeletal sites than those without VF, but no difference in TBS.

CONCLUSIONS

Vertebral fractures are frequent in acromegaly, and are associated with lower BMD but not with TBS. Patients with acromegaly, regardless of gonadal status, have significantly higher BMD but lower TBS than hypogonadal patients. Moreover, disease activity and hypogonadism do not influence BMD, TBS or VF in acromegaly.

Acromegaly and the long-term fracture risk of the vertebra and hip: a national cohort study

In this national cohort study, the patients with acromegaly had significantly higher risks of clinical vertebral (HR 2.09 [1.58-2.78]) and hip (HR 2.52 [1.61-3.95]) fractures than the controls. The increased fracture risk in patients with acromegaly was time-dependent and was observed even during the early period of follow-up.

PURPOSE

Acromegaly is characterized by the overproduction of growth hormone (GH) and insulin-like growth factor-1 (IGF-1), both play important roles in regulating bone metabolism. We investigated the risk of vertebral and hip fractures in patients with acromegaly compared to age- and sex-matched controls.

METHODS

This nationwide population-based cohort study included 1,777 patients with acromegaly aged 40 years or older in 2006-2016 and 8,885 age- and sex-matched controls. A Cox proportional hazards model was used to estimate the adjusted hazard ratio (HR) [95% confidence interval].

RESULTS

The mean age was 54.3 years and 58.9% were female. For approximately 8.5 years of follow-up, the patients with acromegaly had significantly higher risks of clinical vertebral (HR 2.09 [1.58-2.78]) and hip (HR 2.52 [1.61-3.95]) fractures than the controls in the multivariate analyses. There were significant differences in the risks of clinical vertebral (P < 0.0001) and hip (P < 0.0001) fractures between the patients with acromegaly and the controls in the Kaplan-Meier survival analysis. The multivariable-adjusted HRs for clinical vertebral fractures comparing the patients with acromegaly with controls during and excluding the first 7 years of observation were 1.69 [1.15-2.49] and 2.70 [1.75-4.17], respectively. The HRs for hip fractures during and excluding the first 7 years of observation were 2.29 [1.25-4.18] and 3.36 [1.63-6.92], respectively.

CONCLUSIONS

The patients with acromegaly had a higher risk of hip fractures as well as clinical vertebral fractures than the controls. The increased fracture risk in patients with acromegaly was time-dependent and was observed even during the early period of follow-up.

Relationships between sclerostin and morphometric vertebral fractures, bone mineral density, and bone microarchitecture in postmenopausal women

Higher sclerostin levels in postmenopausal women are associated with improved bone microarchitecture, areal and volumetric bone mineral density, and bone strength. However, the serum sclerostin level had no independent associations with the prevalence of morphometric vertebral fractures in this population after multivariable adjustment.

PURPOSE

We aim to investigate the associations between serum sclerostin levels and morphometric vertebral fractures (VFs) prevalence, bone mineral density (BMD), and bone microarchitecture in postmenopausal women.

METHODS

A total of 274 community-dwelling postmenopausal women were randomized enrolled. We collected general information and measured the serum sclerostin level. Morphometric VFs were assessed on the lateral thoracic and lumbar spine X-rays. Areal BMD and calculated trabecular bone score (TBS) were detected by dual-energy X-ray absorptiometry, and volumetric BMD and bone microarchitecture data were acquired from high-resolution peripheral quantitative computed tomography.

RESULTS

The prevalence of morphometric VFs was 18.6% in the cohort, and it was significantly higher in the lowest quartile of the sclerostin group than that in the highest quartile of the sclerostin group (27.9% vs. 11.8%, p<0.05). But the serum sclerostin had no independent association with the prevalence of morphometric VFs after adjusting by age, body mass index, BMD at the lumbar vertebrae 1-4, and fragility fracture history after 50 years old (odds ratio: 0.995, 95% confidence interval: 0.987-1.003, p=0.239). The serum sclerostin level positively correlated with the areal, volumetric BMDs, and TBS. It also had significant positive associations with Tb.BV/TV, Tb.N, Tb.Th, and Ct.Th, and negative associations with Tb.Sp and Tb.1/N.SD.

CONCLUSION

Chinese postmenopausal women with higher serum sclerostin levels had a lower prevalence of morphometric VFs, higher BMDs, and better bone microarchitecture. Nevertheless, the serum sclerostin level had no independent association with the prevalence of morphometric VFs.

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.

Looking at the spine in controlled Acromegaly

Skeletal fragility with high risk of vertebral fractures (VFs) is an emerging complication of growth hormone (GH) hypersecretion. VFs often coexist with spine arthropathy and both clinical conditions negatively impact on quality of life of acromegalic subjects. Management of spine osteopathy and arthropathy in acromegaly could be challenging since both complications can persist or even progress after biochemical control of disease. This article analyzes the latest evidence about possible pathophysiological links between VFs and spine arthropathy in active and controlled acromegaly, as well as the diagnostic and therapeutic aspects concerning the holistic management of acromegalic osteo-arthropathy.

Vertebral Fractures in Acromegaly: A Systematic Review

INTRODUCTION

Acromegaly is characterized by a very particular alteration of bone microarchitecture, leading to increased vertebral fragility. However, due to inconsistent and insufficient evidence, no guidelines are available for the evaluation of this osteopathy.

METHODS

We performed a literature review of studies published between 1968 and January 2022 on the PubMed and SCOPUS databases using the terms "acromegaly" and "vertebral fractures". Twenty-four studies were found eligible for inclusion, published between June 2005 and November 2021. Included studies evaluated acromegaly patients, who were assessed for the presence of vertebral fractures. We excluded case reports, reviews, meta-analyses, letters to the editor, articles not written in English, and research performed on the same set of patients without significant differences in study design. Risk of bias was avoided by following the ROBIS risk of bias recommendations. We executed rigorous data collection, and the results are depicted as a narrative overview, but also, as statistical synthesis. Limitations of the evidence presented in the study include study heterogeneity, small sample sizes, and a small number of prospective studies with short follow-up.

FINDINGS

Data regarding vertebral fractures (VFs) in acromegaly and their influencing factors are variable. Twenty-four studies were included, nine out of which had a prospective design. The smallest group of acromegaly patients had 18 subjects and the largest included 248 patients. Prevalence ranges between 6.5% and 87.1%, although most studies agree that it is significantly higher than in controls. VFs also have a higher incidence (between 5.6% and 42%) and are more frequently multiple (between 46.15% and 71%). Evidence shows that disease activity and active disease duration are influencing factors for the prevalence and incidence of VFs. Nonetheless, hypogonadism does not seem to influence the frequency of VFs. While reports are conflicting regarding the use of bone mineral density in acromegaly, evidence seems to be slightly in favor of it not being associated with VFs. However, trabecular bone score is significantly lower in fractured patients, although no prospective studies are available.

INTERPRETATION

Vertebral fractures evaluation should be performed with regularity in all acromegalic patients, especially in the presence of active disease. Disease activity is an important determinant of vertebral fracture incidence and prevalence, although hypogonadism is less so. To clarify the predictive value of both BMD and TBS for vertebral fractures, additional, larger, prospective studies are necessary.

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.

High Prevalence of Vertebral Fractures Associated With Preoperative GH Levels in Patients With Recent Diagnosis of Acromegaly

CONTEXT

Osteopathy and morphometric vertebral fractures (VFs) are emerging complications in acromegaly. However, the prediction of VFs in this clinical setting is still a matter of uncertainty, and it is debated whether they are an early event in the natural history of the disease.

OBJECTIVE

We aimed to evaluate the prevalence and determinants of morphometric VFs in patients with recently diagnosed acromegaly.

METHODS

We enrolled 92 patients (43 men/49 women) on admission to the neurosurgery unit before transsphenoidal surgery, and compared them with control individuals without secondary forms of osteoporosis and pituitary disorders. We performed a VF assessment on preoperative chest x-ray images and collected biochemical, demographic, and clinical data.

RESULTS

We detected a significantly higher prevalence of VFs (33.7%) in patients with acromegaly than in controls (P = .001). Among the patients with acromegaly and VFs, 12 (38.7%) showed multiple VFs, and 5 (16.1%) showed moderate/severe VFs. Patients with VFs had higher random serum growth hormone (GH) levels than those with no VFs (P = .03), but there was no difference in insulin-like growth factor-1 (IGF-1) (P = .07) and IGF-1/Upper Normal Limit ratio (P = .08). Free 3,5,3'-triiodothyronine was slightly lower in patients with acromegaly and VFs than in those without VFs (P = .05). In multiple logistic analysis, GH was independently associated with risk for VFs (P = .003). The preoperative serum GH cutoff value that predicted VFs was 12 ng/mL.

CONCLUSION

For the first time, high prevalence of radiological VFs is reported in patients with recent diagnosis of acromegaly. Therefore, we can hypothesize that VFs are an early phenomenon of acromegaly and related to GH levels. VF assessment should be included in the workup at the diagnosis of acromegaly.

Characterization of vitamin D metabolism in active acromegaly in the setting of bolus (150,000 IU) cholecalciferol treatment

PURPOSE

To reveal distinctive features of vitamin D metabolism in patients with active acromegaly compared to healthy individuals, particularly in the setting of cholecalciferol treatment.

METHODS

The study group included 34 adults with active acromegaly, and the control group included 30 apparently healthy adults with similar age, sex, and BMI. All participants received a single dose (150,000 IU) of cholecalciferol aqueous solution orally. Laboratory assessments including serum vitamin D metabolites (25(OH)D₃, 25(OH)D₂, 1,25(OH)₂D₃, 3-epi-25(OH)D₃ and 24,25(OH)₂D₃), free 25(OH)D, vitamin D-binding protein (DBP) and parathyroid hormone (PTH) as well as serum and urine biochemical parameters were performed before the intake and on Days 1, 3, and 7 after the administration. All data were analyzed with nonparametric statistics.

RESULTS

Patients with acromegaly had tendency to lower baseline 25(OH)D₃ levels (p = 0.05) and lower 25(OH)D₃ levels (p < 0.05) during the follow-up. They were also characterized by PTH suppression (lower baseline PTH levels and lower prevalence of secondary hyperparathyroidism), altered production of main vitamin D metabolites (higher 1,25(OH)₂D₃ and lower 24,25(OH)₂D₃ levels with corresponding lower 25(ОН)D₃/1,25(ОН)₂D₃ and higher 25(ОН)D₃/24,25(ОН)₂D₃ ratios) as well as concordant biochemical features (higher levels of serum phosphorus and albumin-adjusted calcium levels) throughout the study (p < 0.05). The acromegaly group showed an increase in DBP levels after cholecalciferol intake as opposed to the control group (p < 0.05) and had lower increase in free 25(OH)D levels (p < 0.05). Δ25(OH)D₃ was similar between the groups (p > 0.05), showed a negative correlation with the disease activity markers-both IGF-1 levels (r = -0.44, p < 0.05) and fasting GH levels (r = -0.56, p < 0.05)-and lacked correlation with BMI in the acromegaly group (p > 0.05).

CONCLUSION

Patients with active acromegaly have dysregulated vitamin D metabolism characterized by higher 1,25(ОН)₂D₃, lower 24,25(ОН)₂D₃ and altered DBP production. The response to vitamin D supplementation in acromegaly patients might be influenced by hormonal excess. Obtained results require reproducibility check and further study to develop specific clinical recommendations.

TRIAL REGISTRATION

NCT04844164 (release date: April 9, 2021; retrospectively registered).

Regulation of bone mass in endocrine diseases including diabetes

Hormonal regulation plays a key role in determining bone mass in humans. Both skeletal growth and bone loss in health and disease is critically controlled by endocrine factors and low bone mass is a feature of both excess and deficiency of a broad range of hormones. This article explores the impact of diabetes and thyroid, parathyroid, sex steroid and growth hormone disorders on bone mass and fracture risk. Evidence for current management strategies is provided along with suggested practice points and gaps in knowledge for future research.

Decreased serum Wnt antagonist levels in patients with active acromegaly

OBJECTIVES

The Wnt signalling pathway is an important modulator of bone metabolism. This study aims to clarify the changes in Wnt antagonists in active and biochemically controlled acromegalic patients.

METHODS

We recruited 77 patients newly diagnosed with acromegaly. Of those, 41 patients with complete follow-up data were included. Thirty healthy patients matched for age, sex, and body mass index served as controls. Wnt antagonists [sclerostin (SOST), dickkopf-related protein 1 (DKK-1), and Wnt inhibitory factor 1 (WIF-1)], bone turnover markers [osteocalcin, procollagen type 1 N-terminal propeptide (P1NP), and C-terminal telopeptide of type 1 collagen (CTX)] and the bone remodelling index were investigated at baseline and posttreatment.

RESULTS

Acromegalic patients had higher serum osteocalcin, P1NP, and CTX and a higher bone remodelling index than controls (P < 0.01). Serum SOST, DKK-1 and WIF-1 levels were significantly decreased in patients compared to controls (all P < 0.01). Serum SOST and WIF-1 levels were negatively correlated with growth hormone levels; SOST levels were positively correlated with WIF-1. Posttreatment, serum bone turnover markers and the bone remodelling index decreased, while SOST and WIF-1 significantly increased (P < 0.05). DKK-1 levels did not change compared to baseline (P > 0.05). In biochemically controlled patients, SOST and WIF-1 levels and bone turnover markers were restored and did not differ from those of the control participants (all P > 0.05).

CONCLUSION

Patients with active acromegaly exhibited significantly decreased Wnt antagonist levels. The reduction in Wnt antagonists is a compensatory mechanism to counteract increased bone fragility in active acromegaly.

Low sclerostin levels after long-term remission of acromegaly

PURPOSE

Bone health is compromised in acromegaly resulting in vertebral fractures (VFs), regardless of biochemical remission. Sclerostin is a negative inhibitor of bone formation and is associated with increased fracture risk in the general population. Therefore, we compared sclerostin concentrations between well-controlled acromegaly patients and healthy controls, and assessed its relationship with bone mineral density (BMD), and VFs in acromegaly.

METHODS

Seventy-nine patients (mean age 58.9 ± 11.4 years, 49% women) with controlled acromegaly, and 91 healthy controls (mean age 51.1 ± 16.9 years, 59% women) were included. Plasma sclerostin levels (pg/mL) in patients were measured with an ELISA assay, whereas in controls, serum levels were converted to plasma levels by multiplication with 3.6. In patients, VFs were radiographically assessed, and BMD was assessed using dual X-ray absorptiometry.

RESULTS

Median sclerostin concentration in controlled acromegaly patients was significantly lower than in healthy controls (104.5 pg/mL (range 45.7-234.7 pg/mL) vs 140.0 pg/mL (range 44.8-401.6 pg/mL), p < 0.001). Plasma sclerostin levels were not related to age, current growth hormone (GH) or insulin-like factor-1 (IGF-1) levels, gonadal state, treatment modality, remission duration, or BMD, VF presence, severity or progression.

CONCLUSION

Patients with long-term controlled acromegaly have lower plasma sclerostin levels than healthy controls, as a reflection of decreased osteocyte activity. Further longitudinal studies are needed to establish the course of sclerostin during different phases of disease and its exact effects in acromegalic osteopathy.