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

Mild antiresorptive activity of an anti-vascular endothelial growth factor A antibody and sunitinib in a rat model of bone resorption

Medication-Related-Osteonecrosis-of-the-Jaw (MRONJ) is an adverse event linked to antiresorptives such as bisphosphonates and denosumab. While MRONJ predominantly affects cancer patients treated with these agents, it has been less frequently reported in cancer patients receiving angiogenesis inhibitors (AgIs) like bevacizumab and sunitinib, even without concurrent use of antiresorptives. We hypothesized that certain AgIs exhibit antiresorptive activity in addition to their antiangiogenic effects, potentially influencing the pathophysiology of MRONJ. 52 five-week-old SD rats were randomized to receive vehicle (VEH), an oncologic dose of zoledronic acid (ZOL), or low (LD) and high doses (HD) of either an anti-VEGFA antibody or sunitinib (SU) for 10 days. We used the Schenk assay to assess the in vivo antiresorptive properties of these drugs/agents. We evaluated serum biomarkers of bone resorption (TRACP 5b) and formation (P1NP), pQCT variables of the femurs/tibias, and bone resorption/formation variables by bone histomorphometry at the distal femur metaphysis. ZOL reduced TRACP-5b levels, osteoclast number, and BFR while increasing vBMD, mineralized tissue volume, calcified cartilage volume, and bone volume. Both anti-VEGFA and SU decreased osteoclast number and increased calcified cartilage volume relative to total mineralized tissue volume, though to a lesser extent than ZOL. Anti-VEGFA (HD) also reduced TRACP-5b levels. Furthermore, both AgIs decreased P1NP levels, MAR, and bone elongation rate but increased growth cartilage thickness and induced physeal dysplasia. In conclusion, AgIs, particularly anti-VEGFA, exhibit significant yet milder antiresorptive activity compared to ZOL. They also affect bone formation, suggesting a complex mechanism that may play a role in the pathophysiology of MRONJ.

Multiple pathological bone fractures in a dog with adrenal-dependent Cushing's syndrome

Pathological bone fractures may occur secondarily to Cushing's syndrome in people. Although low bone mineral density due to cortisol excess has been described in dogs, there is no evidence that dogs with Cushing's disease can develop osteoporosis or secondary bone fractures. Here, we report a case of a dog with Cushing's disease and multiple pathological bone fractures. A 14-year-old female spayed mixed-breed dog was attended due to progressive lethargy, weakness, difficulty moving, trembling and clinical signs of Cushing's syndrome (polyuria, polydipsia, alopecia and abdominal distension). After confirmation of the diagnosis of Cushing's disease and 2 days after starting trilostane treatment (0.27 mg/kg every 12 hours), the dog presented to our hospital with reluctance to rise. In the computed tomography scan, decreased bone density in cervical and thoracic vertebrae, ribs scapular bones and multiple rib fractures were detected. Despite 8 days of hospitalisation, reluctance to rise and walk persisted. Given the unfavourable progression of the diseases, the owner opted for euthanasia. Post mortem evaluation confirmed a cortical carcinoma of the left adrenal gland and thin, irregular spicules and trabeculae of compact bone and reduced thickness of the cortex of the ribs.

Hypercalcemia Following Adrenalectomy for Cushing Syndrome in a Patient with Post-Surgical Hypoparathyroidism

Background: Hypercalcemia is a frequently encountered laboratory finding in endocrinology, warranting accurate clinical and laboratory evaluation to identify its cause. While primary hyperparathyroidism and malignancies represent the most common causes, many other etiologies have been described, including some reports of hypercalcemia secondary to adrenal insufficiency. On the contrary, hypoparathyroidism is a relatively common cause of hypocalcemia, often arising as a complication of thyroid surgery. In real-world clinical practice, however, many challenges come into play, and a comprehensive approach may not be enough to establish a diagnosis. Case presentation: we describe a peculiar case of severe hypercalcemia occurring in a 47-year-old woman with a previous history of post-surgical permanent hypoparathyroidism treated with calcitriol (0.5 µg bid) and calcium carbonate (1 g qd), which persisted after withdrawal of these drugs. During her follow-up, an ACTH-independent Cushing syndrome was diagnosed, leading to a unilateral right adrenalectomy. In the two months following surgery, she was admitted to the emergency ward on three occasions because of severe, persistent, idiopathic hypercalcemia. On each occasion, parathyroid hormone levels were confirmed to be undetectable, with low vitamin D levels. Common and rare causes of hypercalcemia were excluded, and the persistence of severely elevated calcium levels led to the empirical use of intravenous clodronate, achieving remission of both hypercalcemia and, unexpectedly, hypoparathyroidism. After 8 months, due to borderline-reduced calcium, calcitriol at 0.5 µg qd was restarted. After 18 months of follow-up, the patient is well and normocalcemic, with low-dose calcitriol. Notably, the patient had no acute adrenal insufficiency, distinguishing this case from other post-adrenalectomy hypercalcemia reports. Conclusions: the history of hypoparathyroidism makes this case even more unusual, and it encourages careful follow-up of hypoparathyroid patients with Cushing syndrome. Ongoing observation, as well as new research on the physiopathology of cortisol and calcium metabolism, are needed to clarify the pathogenesis of this case.

Novel approach to bone comorbidity in resistant acromegaly

Active acromegaly may lead to irreversible complications. Among them, acromegaly osteopathy and fragility (vertebral and hip) fractures have emerged as frequent and precocious events in the natural history of the disease, being correlated with longer disease duration and higher growth hormone (GH) levels, accounting for patients' reported poor quality of life, physical performance and other life-impacting complications. Differently from primary osteoporosis, bone mineral density is not a reliable tool to predict fracture risk in this clinical setting, as patients with active disease frequently have normal or slightly reduced bone mass; whereas bone quality is particularly compromised, as determined by low trabecular bone score (TBS) in patients with active disease as compared to healthy controls or patients with cured/controlled disease. The evidence of impaired bone microstructure has been profoundly investigated with different computed tomography (CT) techniques, reporting low trabecular number and thickness as well as wide but more porous cortical bone, providing an explanation for such a high prevalence of vertebral fractures (up to 40-50% in selected cohorts). Since data on bone-active drugs are scanty, disease control remains a cornerstone to prevent fractures. Nonetheless, some potential protective effects may derive from vitamin D supplementation and pasireotide therapies, independently from disease status. Aim of this manuscript is to review the current and emerging evidence on skeletal fragility in patients with active and resistant acromegaly.

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.

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.

Cross-Disciplinary Approach of Adrenal Tumors: Insights into Primary Aldosteronism-Related Mineral Metabolism Status and Osteoporotic Fracture Risk

Our objective was to overview the novel aspects in the field of adrenal gland neoplasms, namely, the management of bone status with respect to primary aldosteronism (PA). In the current narrative review, a PubMed study was conducted from inception until June 2023. The inclusion criteria were: human (clinically relevant) studies of any study design (at least 10 patients per study); English papers; and the following combination of key words within the title and/or abstract: "aldosterone" AND "bone", "skeleton", "osteoporosis", "fracture", "calcium", "parathyroid", "DXA", "osteocalcin", "P1NP", "alkaline phosphatase", "bone marker", "trabecular bone score", or "FRAX". The exclusion criteria were in vitro or animal studies, reviews, and case reports/series. We screened 1027 articles and finally included 23 studies (13 of case-control type, 3 cross-sectional, 5 prospective, 1 observational cohort, and 1 retrospective study). The assessments provided in these studies were as follows: nine studies addressed Dual-Energy X-ray Absorptiometry (DXA), another study pointed out a bone microarchitecture evaluation underlying trabecular bone score (TBS), and seven studies investigated the bone turnover markers (BTMs) profile. Moreover, 14 studies followed the subjects after adrenalectomy versus medical treatment, and 21 studies addressed secondary hyperparathyroidism in PA patients. According to our study on published data during a period of almost 40 years (n = 23, N = 3965 subjects aged between 38 and 64, with a mean age 56.75, and a female-to-male ratio of 1.05), a higher PTH in PA versus controls (healthy persons or subjects with essential hypertension) is expected, secondary hyperparathyroidism being associated in almost half of the adults diagnosed with PA. Additionally, mineral metabolism anomalies in PA may include lower serum calcium and higher urinary calcium output, all these three parameters being reversible under specific therapy for PA, regardless medical or surgical. The PA subgroup with high PTH seems at higher cardiovascular risk, while unilateral rather than bilateral disease was prone to this PTH anomaly. Moreover, bone mineral density (BMD) according to central DXA might show a higher fracture risk only in certain adults, TBS being a promising alternative (with a still unknown perspective of diabetes' influence on DXA-TBS results in PA). However, an overall increased fracture prevalence in PA is described in most studies, especially with respect to the vertebral site, the fracture risk that seems correctable upon aldosterone excess remission. These data recommend PA as a cause of secondary osteoporosis, a treatable one via PA intervention. There is still an area of debate the way to address BMTs profile in PA, the case's selection toward specific bone evaluation in every day practice, and further on, the understanding of the potential genetic influence at the level of bone and mineral complications in PA patients.

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.

Do bone turnover markers reflect changes in bone microarchitecture during treatment of patients with thyroid dysfunction?

PURPOSE

This study aimed to compare changes in the bone turnover markers (BTMs)-C-terminal telopeptide of type I collagen (CTX-I) and procollagen I N-terminal peptide (PINP)-with changes in the bone microarchitecture, assessed by high-resolution peripheral quantitative computed tomography (HR-pQCT), during treatment of patients with thyroid dysfunction.

METHODS

In women with newly diagnosed hypo- or hyperthyroidism, HR-pQCT variables, obtained from the tibia and the radius, were compared with BTMs. Data were collected at diagnosis and after at least 12 months of euthyroidism.

RESULTS

73 women completed the study (hypothyroidism, n = 27; hyperthyroidism, n = 46). Among hyperthyroid patients, correlations were found between changes in BTMs and HR-pQCT variables, primarily for cortical variables in the tibia, i.e. cortical thickness (CTX-I, p < 0.001; PINP, p < 0.001), and volumetric bone mass density (vBMD) (CTX-I, p < 0.001; PINP, p < 0.001). Moreover, correlations between BTMs and estimated bone strength were found. In the hypothyroid subgroup, no significant findings existed after adjustment. Following treatment, less decrease in tibial vBMD was seen among patients with increasing CTX-I compared to those with a decreasing CTX-I level (p = 0.009). Opposite findings applied to PINP, as patients with decreasing PINP showed an increase in tibial vBMD, in contrast to a decline in this parameter among patients with increasing PINP (p < 0.001).

CONCLUSION

Changes in CTX-I and PINP correlated with HR-pQCT variables during the treatment of women with thyroid dysfunction. To some extent, these BTMs reflected the restoration of bone microarchitecture. CTX-I seems to be the most sensitive BTM in treatment-naïve thyroid diseases, while PINP is more useful for monitoring during treatment.

TRIAL REGISTRATION NUMBER

NCT02005250. Date: December 9, 2013.

Bone Turnover Markers: Basic Biology to Clinical Applications

Bone turnover markers (BTMs) are used widely, in both research and clinical practice. In the last 20 years, much experience has been gained in measurement and interpretation of these markers, which include commonly used bone formation markers bone alkaline phosphatase, osteocalcin, and procollagen I N-propeptide; and commonly used resorption markers serum C-telopeptides of type I collagen, urinary N-telopeptides of type I collagen and tartrate resistant acid phosphatase type 5b. BTMs are usually measured by enzyme-linked immunosorbent assay or automated immunoassay. Sources contributing to BTM variability include uncontrollable components (e.g., age, gender, ethnicity) and controllable components, particularly relating to collection conditions (e.g., fasting/feeding state, and timing relative to circadian rhythms, menstrual cycling, and exercise). Pregnancy, season, drugs, and recent fracture(s) can also affect BTMs. BTMs correlate with other methods of assessing bone turnover, such as bone biopsies and radiotracer kinetics; and can usefully contribute to diagnosis and management of several diseases such as osteoporosis, osteomalacia, Paget's disease, fibrous dysplasia, hypophosphatasia, primary hyperparathyroidism, and chronic kidney disease-mineral bone disorder.

Bone Turnover in Relation to Thyroid-Stimulating Hormone in Hypothyroid Patients on Thyroid Hormone Substitution Therapy

Background. Bone turnover markers (BTMs) have emerged as a useful tool for monitoring bone remodeling activity in the skeleton, and their serum levels correlate with bone loss rates in osteoporotic and normal individuals. Whether the same holds for other metabolic bone diseases is still subject to discussion. Methods. We analyzed the relation between levels of BTMs and TSH in 79 females on thyroid hormone substitution therapy for hypothyroidism. Based on the reference range for TSH (0.2–4.0 mU/L) in our lab, we assessed BTMs in five different groups of patients based on the following criteria: (1) hypothyroidism (TSH >4.0); (2) TSH in the high normal range (1.0–4.0); (3) TSH in the low normal range (0.2–1.0); (4) TSH below the normal range (0.01–0.2); (5) TSH undetectable (<0.01). We studied the relationship between TSH and four different bone markers: procollagen type 1 N-terminal propeptide (PINP), C-terminal cross-linking telopeptide of type 1 collagen (CTX), osteocalcin (OC), and bone specific alkaline phosphatase (BSAP). In a subgroup of patients, bone mineral density was assessed by a DXA scan. Results. PINP emerged as the most sensitive and dynamic BTM for assessment of bone turnover in this patient group, achieving significant rho values on nonparametric correlation analysis for both TSH (rho −0.47; $p=0.0001$ ) and FT4 (rho 0.27; $p=0.018$ ). CTX and OC also revealed significant correlations to TSH, albeit with lower rho values (−0.37 and −0.24, respectively). Categorical analysis showed that bone turnover increased significantly, albeit with pronounced interindividual variability for TSH values below the lower limit of normal (0.2 mU/l), with the most severe affected being women exhibiting suppression of TSH. Further analysis of loss rates by DXA in a limited subgroup of patients showed that this was accompanied by accelerated bone loss. Conclusion. PINP is the most sensitive marker of bone turnover in thyroid disorders. TSH values below the lower limit of normal are associated with increased bone turnover and accelerated bone loss, however, with pronounced interindividual variations. Assessment of PINP may be a valuable tool in cases where there is concern about possible adverse effects of thyroid hormone substitution therapy on bone.

Vertebral fractures, trabecular bone score and their determinants in chronic hypoparathyroidism

PURPOSE

Patients with hypoparathyroidism are at risk of vertebral fractures (VFs) despite high bone mineral density (BMD). We investigated this paradox by assessing trabecular bone score (TBS) and hip structural analysis (HSA) in non-surgical chronic hypoparathyroidism (cHypoPT) with and without VFs.

METHODS

152 cHypoPT patients (age 40.2 ± 13.4 years, M: F = 81:71) with a median follow-up of 8 (2-13) years were assessed for BMD, VFs, TBS, and HSA and compared with 152 healthy controls. VFs at T₇-L₄ were assessed by Genant's method. Average serum total calcium and phosphorus during follow-up were assessed.

RESULTS

The lumbar spine and hip BMD were higher by 25.4 and 13.4% in cHypoPT than controls (P < 0.001). Paradoxically, VFs (30.9 vs.7.9%), including multiple (12.5 vs. 2.6%) were higher in cHypoPT (P < 0.001). Though overall average TBS (1.411 ± 0.091) was normal in cHypoPT, 25.4% of the females had subnormal TBS, more in post than pre-menopausal women (52.3 vs. 14%, P = 0.002) and as compared to males (6.1%, P = 0.001). TBS correlated with menopausal status and follow-up serum calcium-phosphorus product. For every gm/cm² rise in BMD, TBS increase was only 0.227 in cHypoPT compared to 0.513 in controls. Frequency of VFs increased with declining TBS (P = 0.004). HSA was comparable between cHypoPT with and without VFs. 23.4% of cHypoPT with VFs had subnormal TBS.

CONCLUSION

31% of cHypoPT patients had VFs. TBS indicated degraded bone microarchitecture in 50% of the post-menopausal cHypoPT women. However, TBS has limitations to detect abnormal bone microarchitecture in cHypoPT as only one-fourth of patients with VFs showed low TBS.

Which physical activity in patients affected by hypoparathyroidism? A review of the literature and practical recommendations

BACKGROUND

Hypoparathyroidism (HypoP) is a rare endocrine condition characterized by hypocalcaemia and hyperphosphatemia, as a consequence of absent or improperly low parathyroid hormone (PTH) levels. Patients affected by HypoP have a clinical condition often characterized by paresthesias and muscle spasms, as well as long-term consequences as nephrolithiasis, extraskeletal calcification, and fractures. In the literature, likely due to these symptoms, few data exist regarding the appropriate physical activity (PA) in subjects suffering from HypoP.

PURPOSE

This review evaluates the literature on exercise-based approaches to the management of individuals affected by HypoP and evaluates: (1) the effects of physical exercise on muscle cramps and other clinical symptoms; (2) the effects of exercise on PTH and calcium level; (3) the most suitable clinical exercise testing; and (4) the most suitable exercise combination.

METHODS AND RESULTS

A systematic search was conducted using the databases MEDLINE, Google Scholar using "hypoparathyroidism AND Physical Activity", "Training AND hypoparathyroidism", "Exercise AND muscle cramps", "Exercise AND Fatigue" as keywords. In addition, references list from the included articles were searched and cross-checked to identify any further potentially eligible studies. A total of 50 manuscripts were found among which 39 manuscripts were selected. A few clinical studies have been performed in HypoP patients to evaluate PA training protocols.

CONCLUSION

Although further research is needed to draw solid conclusions regarding best PA protocols in subjects affected by HypoP, a PA protocol has been proposed within the manuscript to encourage patients to attempt exercise to improve their clinical conditions and their quality of life.

Patients with Thyroid Disorder, a Contraindication for Dental Implants? A Systematic Review

The thyroid gland is composed of the thyroid follicles, considered to be the functional units of the thyroid gland. The synthesis of the thyroid hormones occurs in these follicles. Triiodothyronine (T3) and thyroxine (T4) are the thyroid hormones and affect metabolic processes all through the body. This systematic evaluation was performed to answer the following PICO question: “Can patients with thyroid disorders undergo dental implant rehabilitation with the same survival rate as patients without thyroid disorders?”. A systematic review of the literature was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statements to gather available and current evidence of thyroid disorders and its relationship with dental implants. The electronic search, in the PubMed and Cochrane databases, yielded 22 articles. Out of the 22 articles, only 11 fulfilled the inclusion criteria. Manual research of the reference list yielded no additional papers. According to the SORT criteria and answering our PICO question, level B can be established to conclude that patients with thyroid disorders can be rehabilitated with dental implants, with similar survival rates as patients without thyroid disorders. Papers with higher scientific evidence and bigger sample size should be carried out.