Effect of hypercortisolism on bone mineral density and bone metabolism: A potential protective effect of adrenocorticotropic hormone in patients with Cushing's disease

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.

Cushing's disease and bone

Bone impairment associated with Cushing's disease (CD) is a complex disorder, mainly involving deterioration of bone quality and resulting in an increased fracture rate, often despite normal bone mineral density. Bone complications are common in patients with CD at the time of diagnosis but may persist even after successful treatment. There is currently no agreement on the optimal diagnostic methods, thresholds for anti-osteoporotic therapy and its timing in CD. In this review, we summarize the current data on the pathophysiology, diagnostic approach and management of bone complications in CD.

Predictors of bone mineral density in patients receiving glucocorticoid replacement for Addison's disease

PURPOSE

Patients receiving long-term glucocorticoid (GC) treatment are at risk of osteoporosis, while bone effects of substitution doses in Addison's disease (AD) remain equivocal. The project was aimed to evaluate serum bone turnover markers (BTMs): osteocalcin, type I procollagen N-terminal propeptide (PINP), collagen C-terminal telopeptide (CTX), sclerostin, DKK-1 protein, and alkaline phosphatase (ALP) in relation to bone mineral density (BMD) during GC replacement.

METHODS

Serum BTMs and hormones were assessed in 80 patients with AD (22 males, 25 pre- and 33 postmenopausal females) on hydrocortisone (HC) substitution for ≥3 years. Densitometry with dual-energy X-ray absorptiometry covered the lumbar spine (LS) and femoral neck (FN).

RESULTS

Among BTMs, only PINP levels were altered in AD. BMD Z-scores remained negative except for FN in males. Considering T-scores, osteopenia was found in LS in 45.5% males, 24% young and 42.4% postmenopausal females, while osteoporosis in 9.0%, 4.0% and 21.1%, respectively. Lumbar BMD correlated positively with body mass (p = 0.0001) and serum DHEA-S (p = 9.899 × 10-6). Negative correlation was detected with HC dose/day/kg (p = 0.0320), cumulative HC dose (p = 0.0030), patient's age (p = 1.038 × 10-5), disease duration (p = 0.0004), ALP activity (p = 0.0041) and CTX level (p = 0.0105). However, only age, body mass, ALP, serum CTX, and sclerostin remained independent predictors of LS BMD.

CONCLUSION

Standard HC substitution does not considerably accelerate BMD loss in AD patients and their serum BTMs: CTX, osteocalcin, sclerostin, DKK-1, and ALP activity remain within the reference ranges. Independent predictors of low lumbar spine BMD, especially ALP activity, serum CTX and sclerostin, might be monitored during GC substitution.

Evaluation of bone-related mechanical properties in female patients with long-term remission of Cushing's syndrome using quantitative computed tomography-based finite element analysis

BACKGROUND

Hypercortisolism in Cushing's syndrome (CS) is associated with bone loss, skeletal fragility, and altered bone quality. No studies evaluated bone geometric and strain-stress values in CS patients after remission thus far.

PATIENTS AND METHODS

Thirty-two women with CS in remission (mean age [±SD] 51 ± 11; body mass index [BMI], 27 ± 4 kg/m2; mean time of remission, 120 ± 90 months) and 32 age-, BMI-, and gonadal status-matched female controls. Quantitative computed tomography (QCT) was used to assess volumetric bone mineral density (vBMD) and buckling ratio, cross-sectional area, and average cortical thickness at the level of the proximal femur. Finite element (FE) models were generated from QCT to calculate strain and stress values (maximum principal strain [MPE], maximum strain energy density [SED], maximum Von Mises [VM], and maximum principal stress [MPS]). Areal BMD (aBMD) and trabecular bone score (TBS) were assessed by dual-energy X-ray absorptiometry (2D DXA).

RESULTS

Trabecular vBMD at total hip and trochanter were lower in CS as compared with controls (P < .05). Average cortical thickness was lower, and buckling ratio was greater in CS vs controls (P < .01). All strain and stress values were higher in CS patients vs controls (P < .05). 2D DXA-derived measures were similar between patients and controls (P > .05). Prior hypercortisolism predicted both VM (β .30, P = .014) and MPS (β .30, P = .015), after adjusting for age, BMI, menopause, delay to diagnosis, and duration of remission.

CONCLUSIONS

Women with prior hypercortisolism have reduced trabecular vBMD and impaired bone geometrical and mechanical properties, which may contribute to an elevated fracture risk despite long-term remission.

Laparoscopic adrenalectomy for adrenal tumors with endocrine activity: Perioperative management pathways for reduced complications and improved outcomes

The major adrenal tumors with endocrine activity are primary aldosteronism, Cushing's syndrome/mild autonomous cortisol secretion, and pheochromocytoma/paraganglioma. Excessive aldosterone secretion in primary aldosteronism causes cardiovascular, renal, and other organ damage in addition to hypertension and hypokalemia. Cortisol hypersecretion in Cushing's syndrome/mild autonomous cortisol secretion causes obesity, hypertension, impaired glucose tolerance, and cardiometabolic syndrome. Massive secretion of catecholamines in pheochromocytoma/paraganglioma causes hypertension and cerebrocardiovascular disease due to rapid blood pressure fluctuation. Moreover, pheochromocytoma multi-system crisis is a feared and possibly fatal presentation of pheochromocytoma/paraganglioma. Thus, adrenal tumors with endocrine activity are considered an indication for adrenalectomy, and perioperative management is very important. They have a risk of perioperative complications, either due to direct hemodynamic effects of the hormone hypersecretion or due to hormone-related comorbidities. In the last decades, deliberate preoperative evaluation and advanced perioperative management have significantly reduced complications and improved outcomes. Furthermore, improvements in anesthesia and surgical techniques with the feasibility of laparoscopic adrenalectomy have contributed to reduced morbidity and mortality. However, there are still several challenges to be considered in the perioperative care of these patients. There are very few data available prospectively to guide clinical management, due to the rarity of adrenal tumors with endocrine activity. Therefore, most guidelines are based on retrospective data analyses or small case series. In this review, the latest knowledge is summarized, and practical pathways to reduce perioperative complications and improve outcomes in adrenal tumors with endocrine activity are presented.

The Significance of Dual-Energy X-ray Absorptiometry (DXA) Examination in Cushing's Syndrome-A Systematic Review

In recent years, the usefulness of dual-energy X-ray absorptiometry (DXA) as a valuable complementary method of assessing the content and distribution of adipose and lean tissue as well as bone mineral density and estimating the risk of fractures has been increasingly confirmed. The diagnosis and treatment of Cushing's syndrome remain challenging, and monitoring the effects of treatment is often necessary. DXA tests offer a potential solution to many problems related to the availability of a quick, detailed, and reliable analysis of changes in the content and distribution of individual body composition components. The article discusses total body DXA scans (FMI, VAT, ALMI), lumbar spine scans (VFA, TBS), and osteoporosis scans (BMD, T-score, Z-score)-all are of potential interest in Cushing's syndrome. The article discusses the use of the most important indicators obtained from a DXA test (FMI, VAT, ALMI, BMD, T-score, Z-score, VFA, TBS) and their clinical significance in Cushing's syndrome was verified. The literature from the last decade was used for the study, available in MEDLINE, Web of Science, and ScienceDirect.

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.

The association of bone mineral density Z-score with the early postoperative remission and characteristics of bone mineral loss in patients with Cushing's disease: a retrospective study

AIM

To investigate the association of bone mineral density (BMD) Z-scores with early-postoperative remission rate and clinical parameters in patients with Cushing's disease (CD).

METHODS

We retrospectively evaluated the records of patients diagnosed with CD. After the exclusion of 230 patients, 87 CD patients were finally enrolled. BMD was determined by dual-energy x-ray absorptiometry (DXA) at the lumbar spine 1-4 (L1-4) and left femur. Early-postoperative remission was defined as a morning cortisol concentration on the first day after surgery of less than 5 μg/dL. The diagnosis of BMD "below the expected range for age" was defined as a Z-score≤-2.00 standard deviations.

RESULTS

DXA results were not significantly associated with early postoperative remission. They also did not significantly differ between eugonadal and menopausal groups. Preoperative morning cortisol significantly negatively but weakly correlated with Z-score of the total femur, while preoperative adrenocorticotropic hormone/cortisol ratio positively but weakly correlated with DXA results of L1-4.

CONCLUSION

The severity of bone loss was not significantly related to the failure of transsphenoidal surgery for Cushing's disease.

The association of bone mineral density Z-score with the early postoperative remission and characteristics of bone mineral loss in patients with Cushing's disease: a retrospective study

AIM

To investigate the association of bone mineral density (BMD) Z-scores with early-postoperative remission rate and clinical parameters in patients with Cushing's disease (CD).

METHODS

We retrospectively evaluated the records of patients diagnosed with CD. After the exclusion of 230 patients, 87 CD patients were finally enrolled. BMD was determined by dual-energy x-ray absorptiometry (DXA) at the lumbar spine 1-4 (L1-4) and left femur. Early-postoperative remission was defined as a morning cortisol concentration on the first day after surgery of less than 5 μg/dL. The diagnosis of BMD "below the expected range for age" was defined as a Z-score≤-2.00 standard deviations.

RESULTS

DXA results were not significantly associated with early postoperative remission. They also did not significantly differ between eugonadal and menopausal groups. Preoperative morning cortisol significantly negatively but weakly correlated with Z-score of the total femur, while preoperative adrenocorticotropic hormone/cortisol ratio positively but weakly correlated with DXA results of L1-4.

CONCLUSION

The severity of bone loss was not significantly related to the failure of transsphenoidal surgery for Cushing's disease.

Hypocalcemia Is a Common Risk Factor for Osteoporosis in Taiwanese Patients with Cushing's Syndrome

Background: Osteoporosis is a cardinal manifestation of Cushing’s syndrome. There is a lack of relevant research on risk factors for osteoporosis among patients with Cushing’s syndrome (CS) in Taiwan. Thus, this study was designed to explore the possible risk factors of osteoporosis. Methods: We gathered patients with a diagnosis of CS between 2001 and 2017 in the Chang Gung Research Database (CGRD). We extracted data including diagnoses and biochemistry from hospital records. The diagnosis of CS was based on ICD-9-CM codes (255.0). Osteoporosis was defined by a T value equal to or less than −2.5 in BMD examination and hypocalcemia was defined as serum calcium concentrations < 8.0 mg/dL. Results: A total of 356 patients with CS who made regular visits to the outpatient department were enrolled in this study. The mean age was 68.6 years, and 74.9% of the patients were female. Of them, 207 patients (58.1%) were diagnosed with osteoporosis. Multivariable logistic regression models indicated that serum calcium level was negatively associated with osteoporosis (OR 0.70, CI 0.54−0.91, p < 0.001) after adjustment for age, sex, and other confounding risk factors. In addition, hypocalcemia was associated with heart failure (HF) (OR 2.14, CI 1.02−4.47, p < 0.05), stroke (OR 2.58, CI 1.21−5.46, p < 0.05) and osteoporosis (OR 3.04, CI 1.24−7.41, p < 0.05) in multivariate analysis. Conclusions: Our study found that lower serum calcium levels were common among patients with CS and osteoporosis. Furthermore, CS patients with HF or stroke had high proportion of hypocalcemia. Therefore, these patients must pay more attention to adequate calcium supplementation and undergo the appropriate osteoporosis drug treatment to reduce the risk of subsequent fracture and disability.

Challenges in the diagnosis and management of glucocorticoid-induced osteoporosis in younger and older adults

OBJECTIVE

Glucocorticoids constitute a considerable risk for developing osteoporosis in both younger and older adults. However, currently available bone imaging modalities and fracture-risk assessment tools do not adequately capture the dramatic changes in bone microarchitecture, heterogeneity of glucocorticoid exposure, the impact of chronic disease and other osteoporosis risk factors on the assessment of osteoporosis in these individuals.

DESIGN

A narrative review is presented, following a systematic search of the literature from 2000 to 2021.

RESULTS

Our current appreciation of glucocorticoid-induced osteoporosis (GIO) is focused on older populations, with limited evidence to guide the investigation, risk assessment and treatment in premenopausal women and men less than 50 years. The impact of the underlying chronic disease on secondary osteoporosis in these younger adults is also poorly understood.

CONCLUSION

Through this narrative review, we provide a comprehensive overview of and recommendations for optimising the management of this common cause of secondary osteoporosis younger and older adults.

Cushing syndrome secondary to a mediastinal carcinoid tumor: a case report

Neuroendocrine tumors (NET) are a rare and diverse set of malignancies that can develop anywhere within the body. ACTH-producing mediastinal NETs often originate from the thymus in the anterior mediastinum and are very rare. Primary diagnostic modalities for NETs include CT scan, MRI, scintigraphy, and Ga-DOTA PET scan. Here we report a case of a young male without any past medical history presenting with hypercortisolism secondary to a middle mediastinal typical carcinoid tumor. The patient underwent a successful resection which reduced serum ACTH levels. To the best of our knowledge, this is the first case of Cushing syndrome caused by a middle mediastinal NET.

Non-Canonical Effects of ACTH: Insights Into Adrenal Insufficiency

Introduction

Adrenocorticotropic hormone (ACTH) is produced from proopiomelanocortin, which is predominantly synthetized in the corticotroph and melanotroph cells of the anterior and intermediate lobes of the pituitary gland and the arcuate nucleus of the hypothalamus. Although ACTH clearly has an effect on adrenal homeostasis and maintenance of steroid hormone production, it also has extra-adrenal effects that require further elucidation.

Methods

We comprehensively reviewed English language articles, regardless of whether they reported the presence or absence of adrenal and extra-adrenal ACTH effects.

Results

In the present review, we provide an overview on the current knowledge on adrenal and extra-adrenal effects of ACTH. In the section on adrenal ACTH effects, we focused on corticosteroid rhythmicity and effects on steroidogenesis, mineralocorticoids and adrenal growth. In the section on extra-adrenal effects, we have analyzed the effects of ACTH on the osteoarticular and reproductive systems, adipocytes, immune system, brain and skin. Finally, we focused on adrenal insufficiency.

Conclusions

The role of ACTH in maintaining the function of the hypothalamic-pituitary-adrenal axis is well known. Conversely, if we broaden our vision and analyze its role as a potential treatment strategy in other conditions, it will be evident in the literature that researchers seem to have abandoned this aspect in studies conducted several years ago. We believe it is worth re-evaluating the role of ACTH considering its noncanonical effects on the adrenal gland itself and on extra-adrenal organs and tissues; however, this would not have been possible without the recent advances in the pertinent technologies.

Novel function of adrenocorticotropic hormone in the stimulation of vascular endothelial growth factor release in healthy children and adolescents: a proof-of-concept study

PURPOSE

To assess the effect of adrenocorticotropic hormone (ACTH) on plasma vascular endothelial growth factor (VEGF) levels in healthy children and adolescents and to inform future work on the effects of ACTH on VEGF in bone.

METHODS

An Institutional Review Board-approved prospective study of 10 healthy subjects, ages 9-17, was conducted to assess the effect of ACTH on plasma VEGF levels. VEGF levels were collected at baseline and every 30 minutes for 3 hours. Cosyntropin (a synthetic ACTH analogue) was administered at a low-dose (1 μg) given at t=0 minutes and a high-dose (250 μg) given at t=60 minutes. A Friedman test was performed comparing baseline to peak VEGF levels after stimulation with low-dose and high-dose cosyntropin.

RESULTS

Peak plasma VEGF levels significantly increased after high-dose cosyntropin compared with baseline (P=0.042). Peak plasma VEGF levels did not significantly increase after low-dose cosyntropin compared to baseline.

CONCLUSION

To our knowledge, this is the first study to demonstrate that ACTH administration causes a significant increase in plasma VEGF levels in humans. This finding may have important implications in the protective effects of ACTH on bone. Decreased bone mineral density and adrenal suppression are common side effects of glucocorticoid use in pediatrics. VEGF increases vascularity and may play a role in reducing glucocorticoid-induced bone disease. Animal studies have shown that ACTH stimulates release of VEGF in osteoblasts, though this effect has yet to be evaluated in humans.

Biochemical bone turnover markers in hormonal disorders in adults: a narrative review

BACKGROUND

Hormonal disorders are often associated with abnormal levels of bone turnover markers (BTMs). N-terminal propeptide of type I procollagen (PINP) and serum C-terminal cross-linking telopeptide of type I collagen (CTX-I) are the reference markers of bone formation and bone resorption, respectively.

METHODS

A comprehensive literature search within the MEDLINE and Web of Science databases was performed.

RESULTS

Acromegaly is associated with higher BTM levels, which decrease during the remission after treatment. Adult-onset growth hormone deficiency is often associated with decreased BTM levels. Growth hormone replacement therapy stimulates bone turnover and increases BTM levels. Hypothyroidism is characterized by general slowing of bone metabolism which is reflected by lower BTM levels. The replacement thyroid hormone therapy increases the bone turnover rate and BTM levels increase. Patients with thyroid cancer receive a suppressive dose of thyroid hormones and may have slightly elevated BTM levels. Patients with overt hyperthyroidism had higher BTM levels and anti-thyroid therapy induces a rapid decrease in the BTM levels. Patients with overt primary hyperparathyroidism have higher BTM levels, whereas those with asymptomatic and normocalcemic hyperparathyroidism usually have normal BTM levels. Hypoparathyroidism is characterized by slightly decreased BTM levels. Cushing's syndrome is characterized consistently by markedly decreased osteocalcin concentration, whereas data on other BTMs are discordant.

CONCLUSIONS

BTMs help us to better understand mechanisms of the impact of hormonal disorders and their treatment on bone metabolism. However, it is unknown whether BTMs may be used to monitor the effect of their treatments on bone in the clinical practice.

Bone phenotype in melanocortin 2 receptor-deficient mice

Considering that stress condition associated with osteoporosis, the hypothalamic-pituitary-adrenal (HPA) axis, which is essential for central stress response system, is implicated in regulating bone mass accrual. Melanocortin 2 receptor (MC2R), the receptor of adrenocorticotropic hormone is expressed in both adrenal gland cells and bone cells. To elucidate the role of HPA axis in bone metabolism, we assessed the skeletal phenotype of MC2R deficient mice (MC2R ^-/- mice). We first examined bone mineral density and cortical thickness of femur using dual x-ray absorptiometry and micro-computed tomography. We then conducted histomorphometric analysis to calculate the static and dynamic parameters of vertebrae in MC2R ^-/- mice. The levels of osteoblastic marker genes were examined by quantitative PCR in primary osteoblasts derived from MC2R ^-/- mice. Based on these observations, bone mineral density of femur in MC2R ^-/- mice was increasing relative to litter controls. Meanwhile, the thickness of cortical bone of femur in MC2R ^-/- mice was remarkably elevated. Moreover, serum osteocalcin level was drastically raised in MC2R ^-/- mice. However, bone histomorphometry revealed that static and dynamic parameters reflecting bone formation and resorption were unchanged in vertebrae of MC2R ^-/- mice compared to the control, indicating that MC2R function may be specific to appendicular bone than axis bone. Taken together, the HPA axis due to deletion of MC2R is involved in bone metabolism.

The Effect of Biochemical Remission on Bone Metabolism in Cushing's Syndrome: A 2-Year Follow-Up Study

Endogenous Cushing's syndrome (CS) is a rare cause of secondary osteoporosis. The long-term consequences for bone metabolism after successful surgical treatment remain largely unknown. We assessed bone mineral density and fracture rates in 89 patients with confirmed Cushing's syndrome at the time of diagnosis and 2 years after successful tumor resection. We determined five bone turnover markers at the time of diagnosis, 1 and 2 years postoperatively. The bone turnover markers osteocalcin, intact procollagen-IN-propeptide (PINP), alkaline bone phosphatase, CTX-I, and TrAcP 5b were measured in plasma or serum by chemiluminescent immunoassays. For comparison, 71 sex-, age-, and body mass index (BMI)-matched patients in whom Cushing's syndrome had been excluded were studied. None of the patients received specific osteoanabolic treatment. At time of diagnosis, 69% of the patients had low bone mass (mean T-score = -1.4 ± 1.1). Two years after successful surgery, the T-score had improved in 78% of patients (mean T-score 2 years postoperatively -1.0 ± 0.9). The bone formation markers osteocalcin and intact PINP were significantly decreased at time of diagnosis (p ≤ 0.001 and p = 0.03, respectively), and the bone resorption marker CTX-I and TrAcP 5b increased. Postoperatively, the bone formation markers showed a three- to fourfold increase 1 year postoperatively, with a moderate decline thereafter. The bone resorption markers showed a similar but less pronounced course. This study shows that the phase immediately after surgical remission from endogenous CS is characterized by a high rate of bone turnover resulting in a striking net increase in bone mineral density in the majority of patients. © 2020 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.

The Impact of Mild Autonomous Cortisol Secretion on Bone Turnover Markers

CONTEXT

Several studies have reported increased risk of fragility fractures in patients with mild autonomous cortisol secretion (MACS), discordant to the degree of bone density deterioration.

OBJECTIVE

To evaluate the effect of MACS on bone metabolism in patients with adrenal adenomas.

DESIGN

Cross-sectional study with prospective enrollment, 2014-2019.

SETTING

Referral center.

PATIENTS

213 patients with adrenal adenomas: 22 Cushing syndrome (CS), 92 MACS and 99 nonfunctioning adrenal tumors (NFAT).

MAIN OUTCOME MEASURES

Osteocalcin, procollagen I intact N-terminal (PINP), C-terminal telopeptide (CTX), sclerostin.

RESULTS

Patients with CS demonstrated lower markers of bone formation compared with patients with MACS and NFAT (CS vs MACS vs NFAT: mean osteocalcin 14.8 vs 20.1 vs 21.3 ng/mL [P < 0.0001]; mean PINP 34.8 vs 48.7 vs 48.5 µg/L [P = 0.003]). Severity of cortisol excess was inversely associated with sclerostin (CS vs MACS vs NFAT: mean sclerostin 419 vs 538 vs 624 ng/L, [P < 0.0001]). In a multivariable model of age, sex, body mass index, cortisol, and bone turnover markers, sclerostin was a significant predictor of low bone mass in patients with MACS (OR 0.63 [CI 95%, 0.40-0.98] for each 100 ng/L of sclerostin increase).After adrenalectomy, osteocalcin, CTX, and sclerostin increased by a mean difference of 6.3 ng/mL, 0.12 ng/mL, and 171 pg/mL (P = 0.02 for all), respectively.

CONCLUSIONS

Lower sclerostin level in patients with MACS reflects a reduction in osteocyte function or number associated with exposure to chronic cortisol excess. Increase in bone turnover markers after adrenalectomy suggests restoration of favorable bone metabolism.

Iron Overload Associated Endocrine Dysfunction Leading to Lower Bone Mineral Density in Thalassemia Major

CONTEXT

Patients with thalassemia major (TM) have a lower bone mineral density (BMD) and higher risk of fracture than the general population. The possible mechanisms include anemia, iron overload, malnutrition, and hormonal deficiency, but these have not been thoroughly investigated.

OBJECTIVE

To identify major mineral and hormonal factors related to BMD in adult TM patients to provide human evidence for the proposed mechanisms.

DESIGN

Retrospective study.

SETTING

Referral center.

PATIENTS

Twenty-nine patients with β-TM, aged 23 to 44 years who were followed-up during 2017 to 2018 were enrolled.

OUTCOME MEASUREMENTS

Endocrine profiles, including thyroid, parathyroid, and pituitary function, glucose, vitamin D, calcium, phosphate, and fibroblast growth factor 23 (FGF23) were obtained. The relationships among the above parameters, body height, fractures, and BMD were analyzed.

RESULTS

Abnormal BMD was observed in 42.9% of women and 23.1% of men. The mean final heights of women and men were 3.7 cm and 7.3 cm lower than the mean expected values, respectively. Fracture history was recorded in 26.7% of women and 35.7% of men. BMD was negatively correlated with parathyroid hormone, FGF23, thyrotropin, and glycated hemoglobin (HbA1c) levels, and positively correlated with testosterone, IGF-1, and corticotropin levels (all P < .05). Moreover, hypothyroidism was associated with lower BMD in both the lumbar spine (P = .024) and the femoral neck (P = .004). Patients with hypothyroidism had a higher percentage of abnormal BMD (P = .016).

CONCLUSION

Hypothyroidism, higher HbA1c, and lower adrenocorticotropin were predictors of abnormal BMD in patients with β-TM. Whether the correction of these factors improves BMD warrants further research.

The high-density lipoprotein receptor Scarb1 is required for normal bone differentiation in vivo and in vitro

We examined bone formation and turnover in high-density lipoprotein (HDL) receptor, scavenger receptor type I (Scarb1), knockout animals relative to wild-type (WT) controls. Scarb1-/- animals have elevated serum adrenocorticotropic hormone (ACTH) due to the role of Scarb1 in glucocorticoid production, which might cause increased bone mass. However, this was not observed: Scarb1-/- mice, with ACTH, over 1000 pg/ml relative to wild-type ACTH ~ 25 pg/ml, bone of the knockout animals was osteopenic relative to the wild type at 16 weeks, including bone volume/total volume and trabecular thickness. Other serum parameters of WT and Scarb1-/- animals in cortisol or calcium were unaffected, although Scarb1-/- animals had significantly elevated PTH and decreased phosphate. Osteoblast and osteoclast-related mRNAs extracted from bone were greatly decreased at 8 or 16 weeks. Importantly, in normal ACTH, osteogenic differentiation in vitro from mesenchymal stem cells showed reduced alkaline phosphatase and mineralization. In Scarb1-/- cells relative to WT, mRNAs for RunX2, alkaline phosphatase, type I collagen, and osteocalcin were reduced 40-90%, all p < 0.01, indicating a role of Scarb1 in osteoblast differentiation independent of ACTH. Additionally, in vitro osteoblast differentiation at variable ACTH in WT cells confirmed ACTH increasing bone differentiation, mineralization, alkaline phosphatase, and osteocalcin mRNA at 0-10 nM ACTH, but reduced bone differentiation at 100-1000 nM ACTH. Overall Scarb1-/- animals show inhibited bone formation with age. This may be a mixed effect on direct bone formation and of very high ACTH. Further, this work shows that both ACTH concentration and the HDL receptor Scarb1 play important independent roles in osteoblast differentiation.

Enkephalins and ACTH in the mammalian nervous system

The pentapeptides methionine-enkephalin and leucine-enkephalin belong to the opioid family of peptides, and the non-opiate peptide adrenocorticotropin hormone (ACTH) to the melanocortin peptide family. Enkephalins/ACTH are derived from pro-enkephalin, pro-dynorphin or pro-opiomelanocortin precursors and, via opioid and melanocortin receptors, are responsible for many biological activities. Enkephalins exhibit the highest affinity for the δ receptor, followed by the μ and κ receptors, whereas ACTH binds to the five subtypes of melanocortin receptor, and is the only member of the melanocortin family of peptides that binds to the melanocortin-receptor 2 (ACTH receptor). Enkephalins/ACTH and their receptors exhibit a widespread anatomical distribution. Enkephalins are involved in analgesia, angiogenesis, blood pressure, embryonic development, emotional behavior, feeding, hypoxia, limbic system modulation, neuroprotection, peristalsis, and wound repair; as well as in hepatoprotective, motor, neuroendocrine and respiratory mechanisms. ACTH plays a role in acetylcholine release, aggressive behavior, blood pressure, bone maintenance, hyperalgesia, feeding, fever, grooming, learning, lipolysis, memory, nerve injury repair, neuroprotection, sexual behavior, sleep, social behavior, tissue growth and stimulates the synthesis and secretion of glucocorticoids. Enkephalins/ACTH are also involved in many pathologies. Enkephalins are implicated in alcoholism, cancer, colitis, depression, heart failure, Huntington's disease, influenza A virus infection, ischemia, multiple sclerosis, and stress. ACTH plays a role in Addison's disease, alcoholism, cancer, Cushing's disease, dermatitis, encephalitis, epilepsy, Graves' disease, Guillain-Barré syndrome, multiple sclerosis, podocytopathies, and stress. In this review, we provide an updated description of the enkephalinergic and ACTH systems.

Evaluation of bone health in patients with adrenal tumors

PURPOSE OF REVIEW

Adrenal tumors occur in 5% of population with higher prevalence in elderly. Patients with adrenal tumors present with overt hormonal excess in up to 15% of cases, and mild autonomous cortisol secretion in 30-40% of cases. Overt Cushing syndrome, mild autonomous cortisol secretion, pheochromocytoma, and primary aldosteronism have been associated with higher cardiovascular morbidity and mortality. Increasing experimental and clinical evidence also suggests that adrenal hormone excess is detrimental to bone health. This review aims to discuss the effect of cortisol, aldosterone, and catecholamine excess on bone metabolism, secondary osteoporosis, and fragility fractures.

RECENT FINDINGS

Several studies have reported that patients with hormonally active adrenal tumors demonstrate increased prevalence of fragility fractures incongruous to bone density scan findings. The utility of dual absorptiometry X-ray (DXA) in diagnosing secondary osteoporosis is unclear in patients with cortisol, aldosterone, and catecholamine excess. Trabecular bone score and bone turn over markers could serve as potential diagnostic tools in assessment of severity of bone disease in patients with hormonally active adrenal tumors.

SUMMARY

Adrenalectomy is the mainstay of therapy in patients with overt hormone production. Appropriate case detection strategies to identify patients at risk of fragility fractures are needed in patients not treated with adrenalectomy, such as bilateral primary aldosteronism and mild autonomous cortisol secretion.