Thyroid and bone

The influence of proliferative tissue on Hounsfield unit and its correlation with BMD in middle-aged and elderly patients with lumbar degenerative diseases

PURPOSE

The difference of Hounsfield Unit (HU) value in different regions of L3 vertebra in middle-aged and elderly patients with lumbar degeneration diseases (LDD) was analyzed. To investigate the influence of proliferative tissue on HU value of cancellous bone and its correlation with bone mineral density (BMD).

METHODS

The medical records of middle-aged and elderly patients with LDD in our hospital from December 2020 to December 2023 were retrospectively analyzed. The patients were divided into osteophyte group and no-osteophyte group according to the presence or absence of osteophyte formation on lumbar spine X-ray. In osteophyte group, cancellous bone HU value, containing cortical bone overall HU value and containing osteophyte overall HU value in L3 vertebra were measured on the lumbar CT cross-section. In no-osteophyte group, only the cancellous bone HU value and the containing cortical bone overall HU value were measured. Differences in HU value in different regions of the L3 vertebral body were compared within and between groups of middle-aged and elderly patients with LDD, respectively. To investigate its effect on cancellous bone HU measurements and to do a correlation analysis with patients' BMD.

RESULTS

A total of 115 patients with LDD were included in this study, including 65 males and 50 females, with an average age of 67.83 ± 6.59 years. The results of the study showed no statistical differences in age (P = 0.15), gender (P = 0.57), smoking (P = 0.88), drinking history (P = 0.76), medical history (P > 0.05) and BMI(P = 0.29) between the two groups. In osteophyte group, the mean cancellous bone HU value was 98.00 ± 25.50 HU, the containing cortical bone overall HU value was 189.02 ± 46.18 HU, and the containing osteophyte overall HU value was 232.69 ± 56.01 HU. The overall HU values containing cortical bone and containing osteophyte were significantly higher than cancellous bone HU value (P < 0.001). In no-osteophyte group, the mean cancellous bone HU value was 102.04 ± 19.64 HU, and the containing cortical bone overall HU value was 175.00 ± 28.97 HU, which was statistically significantly different (P < 0.001). There was no significant difference in cancellous bone HU value and the containing cortical bone overall HU value between the two groups (P > 0.05). The results of the Pearson correlation analysis showed a significant correlation between the cancellous bone HU value of the L3 vertebrae and the QCT BMD value of the patients (r = 0.95, P < 0.001). However, there was no significant correlation between containing cortical bone overall HU value and containing osteophyte overall HU value and the patient's QCT BMD value (P > 0.05).

CONCLUSIONS

Vertebral HU value is an alternative measurement that effectively reflects the patient's BMD. In middle-aged and elderly LDD patients, HU values in different areas of L3 vertebra are significantly different, and hyperplastic tissues such as cortical bone and osteophytes may exponentially lead to higher HU value in patients. Compared with other measurement areas, vertebral cancellous bone HU value have the advantage of accurately assessing patients' BMD.

Bone and Joint-on-Chip Platforms: Construction Strategies and Applications

Organ-on-a-chip, also known as "tissue chip," is an advanced platform based on microfluidic systems for constructing miniature organ models in vitro. They can replicate the complex physiological and pathological responses of human organs. In recent years, the development of bone and joint-on-chip platforms aims to simulate the complex physiological and pathological processes occurring in human bones and joints, including cell-cell interactions, the interplay of various biochemical factors, the effects of mechanical stimuli, and the intricate connections between multiple organs. In the future, bone and joint-on-chip platforms will integrate the advantages of multiple disciplines, bringing more possibilities for exploring disease mechanisms, drug screening, and personalized medicine. This review explores the construction and application of Organ-on-a-chip technology in bone and joint disease research, proposes a modular construction concept, and discusses the new opportunities and future challenges in the construction and application of bone and joint-on-chip platforms.

Environmental perchlorate, thiocyanate, and nitrate exposures and bone mineral density: a national cross-sectional study in the US adults

Associations of perchlorate, thiocyanate, and nitrate exposures with bone mineral density (BMD) in adults have not previously been studied. This study aimed to estimate the associations of individual and concurrent exposure of the three chemicals with adult BMD. Based on National Health and Nutrition Examination Survey (NHANES, 2011-2018), 1618 non-pregnant adults (age ≥ 20 years and 47.0% female) were included in this study. Survey-weighted linear regression models were used to estimate individual urinary perchlorate, thiocyanate, and nitrate concentrations with lumbar spine BMD and total BMD in adults. Then, weighted quantile sum (WQS) regression and Bayesian kernel machine regression (BKMR) models were conducted to evaluate associations of co-occurrence of the three chemicals with adult BMD. In all participants, nitrate exposure was inversely associated with lumbar spine BMD (β =  - 0.054, 95%CI: - 0.097, - 0.010). In stratification analyses, significant inverse associations were observed in female and participants older than 40 years old. In WQS regressions, significant negative associations of the weighted sum of the three chemicals with total and lumbar spine BMD (β =  - 0.014, 95%CI: - 0.021, - 0.007; β =  - 0.011, 95%CI: - 0.019, - 0.004, respectively) were found, and the dominant contributor was nitrate. In the BKMR models, non-linear dose-response associations of nitrate exposure with lumbar spine and total BMD were observed. These findings suggested that environmental perchlorate, thiocyanate, and nitrate exposure may reduce adult BMD and nitrate is the main contributor.

Association between thymic hyperplasia and serum calcium level in Graves' disease

BACKGROUND

Graves' disease increases bone resorption in hyperthyroidism, leading to elevated serum calcium levels and a negative bone balance. Thymic hyperplasia is observed in some Graves' disease patients. What's more, there have been a few reports of increased serum calcium and severe osteoporosis induced by Graves' disease with thymic hyperplasia. It remains unclear whether Graves' disease with thymic hyperplasia is associated with higher serum calcium levels. Our study aimed to investigate the possibility of elevated serum calcium levels and aggravated bone mobilization in Graves' disease patients with thymic hyperplasia.

METHODS

Newly diagnosed and untreated patients with Graves' disease (n = 96) were enrolled. They were divided into two groups based on the incidental detection of thymic hyperplasia during imaging. Albumin, alkaline phosphatase, calcium, free triiodothyronine, free thyroxine, thyroid-stimulating hormone, and thyrotrophin receptor antibody (TRAb) were measured, and a computerized tomography of the chest was obtained.

RESULTS

Patients with Graves' disease who had thymic hyperplasia were notably younger (P=0.018) and exhibited higher serum calcium levels (P=0.001) compared to those with Graves' disease without thymic hyperplasia. In the multiple regression analysis, thymic hyperplasia, TRAb, and female gender were significant variables associated with elevated serum calcium levels in patients with Graves' disease, collectively accounting for 31.7% of the variation in serum calcium.

CONCLUSIONS

Graves' disease patients with thymic hyperplasia showed higher serum calcium levels. thymic hyperplasia, TRAb, and female gender were found to be correlated with increased serum calcium levels in Graves' disease, suggesting a potential association between thymic hyperplasia and bone mobilization in Graves' disease.

Selected musculoskeletal disorders in patients with thyroid dysfunction, diabetes, and obesity

Many medical conditions affect the skeletal system and constitute independent risk factors for fractures. The action of thyroid hormones is necessary to maintain adequate development, mineralization, and bone strength. Untreated hyperthyroidism can lead to a decrease in bone mineral density (BMD), osteoporosis, and pathological fractures. In hypothyroidism, the changes in the quality of bone structure lead to an increase in the frequency of fractures. Excessive body weight negatively impacts fracture risk, increases the risk of osteoarthritis and accelerates the development of rheumatoid arthritis and osteoporosis. Type 1 and type 2 diabetes are associated with an increased risk of bone fractures despite different etiopathogenesis due to the duration of the disease and the pro-inflammatory state, the incorporation of advanced glycation end products (AGEs) into the bone matrix, and microvascular disorders. This study summarizes the current literature on the influence of thyroid dysfunction, obesity, and diabetes on the skeletal system.

Subclinical hypothyroidism is not associated with femoral osteoporosis in individuals aged 50 years or older

BACKGROUND

Thyroid dysfunction and osteoporosis are conditions strongly associated with aging, and the prevalence of both conditions is expected to increase in the coming decades. Thyroid hormones regulate bone metabolism, and the role of subclinical hypothyroidism on bone mineral density (BMD) is still controversial. Hence, this study aims to assess the association of subclinical hypothyroidism with femoral osteopenia and osteoporosis in individuals aged 50 years or older.

METHODOLOGY

This retrospective cohort study was carried out with 864 outpatients having at least one result for TSH levels before the first record of dual-energy X-ray absorptiometry (DXA). The primary endpoints were osteopenia (-2.5 standard deviation (SD) <T-score <-1.0SD) and osteoporosis (T-score ≤-2.5SD). Cox proportional hazards regression assessed the association of subclinical hypothyroidism (TSH ≥4.5 mIU/L) with osteopenia and osteoporosis in unadjusted and covariate-adjusted models. Hazard ratios (HR) and 95% confidence intervals (95%CI) were calculated, and p-values <0.05 were considered statistically significant.

RESULTS

There was no significant association between subclinical hypothyroidism and femoral osteopenia in either unadjusted [HR: 1.149 (0.835-1.580); p=0.394] or fully covariate-adjusted models [HR: 1.069 (0.774-1.477); p=0.687]. Subclinical hypothyroidism was associated with femoral osteoporosis in the unadjusted analysis [HR: 1.981 (1.044-3.757); p= 0.036], but a lack of association occurred and remained after successive covariate-adjustments analyses [HR: 1.392 (0.615-3.152); p=0.428].

CONCLUSION

Subclinical hypothyroidism is not independently associated with either femoral osteopenia or osteoporosis in individuals aged 50 years or older over a four-year follow-up time.

A Novel Strategy for Selective Thyroid Hormone Determination Based on an Electrochemical Biosensor with Graphene Nanocomposite

This article presents a novel and selective electrochemical bioassay with antibody and laccase for the determination of free thyroid hormone (free triiodothyronine, fT3). The biosensor was based on a glassy carbon electrode modified with a Fe₃O₄@graphene nanocomposite with semiconducting properties, an antibody (anti-PDIA3) with high affinity for fT3, and laccase, which was responsible for catalyzing the redox reaction of fT3. The electrode modification procedure was investigated using a cyclic voltammetry technique, based on the response of the peak current after modifications. All characteristic working parameters of the developed biosensor were analyzed using differential pulse voltammetry. Obtained experimental results showed that the biosensor revealed a sensitive response to fT3 in a concentration range of 10-200 µM, a detection limit equal to 27 nM, and a limit of quantification equal to 45.9 nM. Additionally, the constructed biosensor was selective towards fT3, even in the presence of interference substances: ascorbic acid, tyrosine, and levothyroxine, and was applied for the analysis of fT3 in synthetic serum samples with excellent recovery results. The designed biosensor also exhibited good stability and can find application in future medical diagnostics.

Reduced Bone Mass and Increased Osteocyte Tartrate-Resistant Acid Phosphatase (TRAP) Activity, But Not Low Mineralized Matrix Around Osteocyte Lacunae, Are Restored After Recovery From Exogenous Hyperthyroidism in Male Mice

Hyperthyroidism causes secondary osteoporosis through favoring bone resorption over bone formation, leading to bone loss with elevated bone fragility. Osteocytes that reside within lacunae inside the mineralized bone matrix orchestrate the process of bone remodeling and can themselves actively resorb bone upon certain stimuli. Nevertheless, the interaction between thyroid hormones and osteocytes and the impact of hyperthyroidism on osteocyte cell function are still unknown. In a preliminary study, we analyzed bones from male C57BL/6 mice with drug-induced hyperthyroidism, which led to mild osteocytic osteolysis with 1.14-fold larger osteocyte lacunae and by 108.33% higher tartrate-resistant acid phosphatase (TRAP) activity in osteocytes of hyperthyroid mice compared to euthyroid mice. To test whether hyperthyroidism-induced bone changes are reversible, we rendered male mice hyperthyroid by adding levothyroxine into their drinking water for 4 weeks, followed by a weaning period of 4 weeks with access to normal drinking water. Hyperthyroid mice displayed cortical and trabecular bone loss due to high bone turnover, which recovered with weaning. Although canalicular number and osteocyte lacunar area were similar in euthyroid, hyperthyroid and weaned mice, the number of terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL)-positive osteocytes was 100% lower in the weaning group compared to euthyroid mice and the osteocytic TRAP activity was eightfold higher in hyperthyroid animals. The latter, along with a 3.75% lower average mineralization around the osteocyte lacunae in trabecular bone, suggests osteocytic osteolysis activity that, however, did not result in significantly enlarged osteocyte lacunae. In conclusion, we show a recovery of bone microarchitecture and turnover after reversal of hyperthyroidism to a euthyroid state. In contrast, osteocytic osteolysis was initiated in hyperthyroidism, but its effects were not reversed after 4 weeks of weaning. Due to the vast number of osteocytes in bone, we speculate that even minor individual cell functions might contribute to altered bone quality and mineral homeostasis in the setting of hyperthyroidism-induced bone disease. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

The risk between thyrotropin suppression and bone mineral density in differentiated thyroid cancer

BACKGROUND

The effect of thyroid stimulating endocrine (TSH) suppression medical aid on bone mineral density (BMD) of patients with differentiated thyroid carcinoma (DTC) or differentiated thyroid malignant neoplastic disease is still controversial. Our aim was to investigate the effect of TSH suppression therapy on BMD of patients with DTC.

METHODS

A total of 1651 DTC patients with TSH-suppression medical care were analyzed by RevMan 5.3 software (https://training.cochrane.org/online-learning/core-software/revman/revman-5-download) in the present study. The PubMed and Embase databases were consistently hunted for works revealed through July 29, 2022.

RESULTS

The results indicated that a significant association between femoral bone mineral density (FN-BMD) (P = .02) or lumbar spine bone mineral density (L-BMD) (P = .04) and DTC patients with TSH-suppression therapy. However, the total hip bone mineral density (TH-BMD) was not significantly related to DTC patients with TSH-suppression therapy (P = .11). For premenopausal women, it was shown that TH-BMD (P = .02) or L-BMD (P = .01) were closely related to DTC patients with TSH-suppression therapy. However, there was no relationship between FN-BMD and DTC patients with TSH-suppression therapy (P = .06). For postmenopausal women, TH-BMD was closely related to DTC patients with TSH-suppression therapy (P = .02). It was revealed that there was no significant difference between L-BMD (P = .16) or FN-BMD (P = .26) and DTC patients with TSH-suppression therapy. For men, there was no relationship between FN-BMD (P = .94) or L-BMD (P = .29) and DTC patients with TSH-suppression therapy.

CONCLUSION

Our systematic review has demonstrated that TSH inhibition treatment mainly influence the TH-BMD or L-BMD of the DTC patients who were premenopausal women; the TH-BMD of the DTC patients who were postmenopausal women. In addition, there was no influence on the FN-BMD or L-BMD of the DTC patients who were men.

Rickets in a child with prolonged acquired hypothyroidism secondary to Hashimoto's thyroiditis

Summary

Skeletal abnormalities with delayed bone age and decreased linear bone growth are commonly found in children with prolonged juvenile hypothyroidism. However, rachitic bone abnormalities have not been previously reported in children with acquired hypothyroidism. Here, we present a case of newly found rickets in an 8-year-old female with untreated acquired hypothyroidism secondary to Hashimoto's thyroiditis. Laboratory finding for abnormalities in calcium/phosphorus homeostasis and hormones that regulate skeletal health was normal. Her radiographic anomalies resolved with levothyroxine treatment alone, suggesting that hypothyroidism was the etiology of the rickets. To our knowledge, this is the first case report of rickets associated with long-standing severe acquired hypothyroidism that resolved exclusively with thyroid repletion.

Learning points

Thyroid hormone plays an important role in bone mineralization. Prolonged hypothyroidism can result in rachitic bone abnormalities noted on radiographs. Hypothyroidism should be considered in the evaluation of a child with rickets.

Thyroid and bone turnover markers in type 2 diabetes: results from the METAL study

OBJECTIVE

We aimed to evaluate whether thyroid hormones, autoimmune and thyroid homeostasis status were related to bone turnover in type 2 diabetes.

METHODS

The data were obtained from a cross-sectional study, the METAL study. In this study, 4209 participants (2059 men and 2150 postmenopausal women) with type 2 diabetes were enrolled. Thyroid function, thyroid antibodies and three bone turnover markers (BTMs), including a large N-mid fragment of osteocalcin (N-MID osteocalcin), β-C-terminal cross-linked telopeptides of type I collagen (β-CTX) and procollagen type I N-terminal propeptide (P1NP), were measured. Thyroid homeostasis parameters, including the sum activity of step-up deiodinases (SPINA-GD), thyroid secretory capacity (SPINA-GT), Jostel's TSH index (TSHI) and the thyrotroph thyroid hormone resistance index (TTSI), were calculated. The associations of thyroid parameters with BTMs were analyzed using linear regression.

RESULTS

Free and total triiodothyronine were positively associated with N-MID osteocalcin and P1NP in both sexes and positively associated with β-CTX in postmenopausal women. Thyroid-stimulating hormone was negatively associated with β-CTX in postmenopausal women, and free thyroxine was negatively associated with N-MID osteocalcin and P1NP in men. SPINA-GD was positively associated with N-MID osteocalcin and P1NP in both sexes. There was a positive relationship of SPINA-GT with β-CTX, a negative relationship of TTSI with β-CTX, and a negative relationship of TSHI with β-CTX and P1NP in postmenopausal women.

CONCLUSIONS

Among men and postmenopausal women with type 2 diabetes, significant associations were observed between N-MID osteocalcin, β-CTX and P1NP with thyroid function and thyroid homeostasis. Further prospective studies are warranted to understand the causal relationship and underlying mechanism.

Developmental toxicity of bromoacetamide via the thyroid hormone receptors-mediated disruption of thyroid hormone homeostasis in zebrafish embryos

Bromoacetamide (BAcAm) is a nitrogenous disinfection by-product. We previously found that BAcAm induced developmental toxicity in zebrafish embryos, but the underlying mechanisms remain to be elucidated. Since thyroid hormones (THs) homeostasis is crucial to development, we hypothesized that disruption of THs homeostasis may play a role in the developmental toxicity of BAcAm. In this study, we found BAcAm exposure significantly increased mortality and malformation rate, decreased hatching rate and body length, inhibited the locomotor capacity in zebrafish embryos. BAcAm elevated TSH, T₃ and T₄ levels, down-regulated T₃/T₄ ratios, and up-regulated mRNA expression changes of THs related genes (trh, tsh, tg, nis, tpo, dio1, dio2, ugt1ab，klf9 and rho), but down-regulated mRNA expression changes of TH receptors (tr α and tr β). Up-regulated tr α and tr β mRNAs by rescue treatment confirmed that both tr α and tr β were involved in the developmental toxicity of BAcAm. In conclusion, our study indicates disruption of THs homeostasis via the thyroid hormone receptors was responsible for the developmental toxicity of BAcAm.

Differences in pathways contributing to thyroid hormone effects on postnatal cartilage calcification versus secondary ossification center development

The proximal and distal femur epiphyses of mice are both weight-bearing structures derived from chondrocytes but differ in development. Mineralization at the distal epiphysis occurs in an osteoblast-rich secondary ossification center (SOC), while the chondrocytes of the proximal femur head (FH), in particular, are directly mineralized. Thyroid hormone (TH) plays important roles in distal knee SOC formation, but whether TH also affects proximal FH development remains unexplored. Here, we found that TH controls chondrocyte maturation and mineralization at the FH in vivo through studies in thyroid stimulating hormone receptor (Tshr^-/-) hypothyroid mice by X-ray, histology, transcriptional profiling, and immunofluorescence staining. Both in vivo and in vitro studies conducted in ATDC5 chondrocyte progenitors concur that TH regulates expression of genes that modulate mineralization (Ibsp, Bglap2, Dmp1, Spp1, and Alpl). Our work also delineates differences in prominent transcription factor regulation of genes involved in the different mechanisms leading to proximal FH cartilage calcification and endochondral ossification at the distal femur. The information on the molecular pathways contributing to postnatal cartilage calcification can provide insights on therapeutic strategies to treat pathological calcification that occurs in soft tissues such as aorta, kidney, and articular cartilage.

T4 rather than TSH correlates with BMD among euthyroid adults

PURPOSE

The objective of this study was to evaluate the association between thyroid hormone and bone mineral density (BMD) among euthyroid adults.

METHODS

This cross-sectional study researched the information from the National Health and Nutrition Examination Survey 2007-2010. We included 3,759 euthyroid participants finally. We used multivariate linear regression models to evaluate the linear relationship between the thyroid hormone profile and BMD. Subgroup analyses stratified by gender and age were further performed. Moreover, the nonlinear relationship was characterized by fitted smoothing curves and generalized additive models, and logistic regression models were used to determine the association of thyroid-stimulating hormone (TSH) and thyroxine (T4) with previous fractures.

RESULTS

The weighted multivariable linear regression models showed no association between TSH and BMD. Free thyroxine (FT4), T4, free triiodothyronine (FT3), and total triiodothyronine (T3) were negatively associated with the total femur BMD and the total spine BMD after adjusting for all covariates. Subgroup analyses demonstrated that all groups had a negative association between T4 and BMD, even in patients with osteopenia/osteoporosis. The nonlinear relationship characterized by smooth curve fittings and generalized additive models suggested that an obvious U-shaped, an inverted U -shaped, and an L - shaped curve was exhibited between thyroid hormone and BMD in the different subgroups. In addition, normal high-level T4 was associated with an increased prevalence of previous fractures than normal low-level T4.

CONCLUSIONS

In this sample of euthyroid adults, T4 exhibits a negative correlation with BMD, regardless of age and gender, in subjects with either normal or lowered BMD. Moreover, high-normal FT4 was associated with an increased prevalence of previous fractures. TSH was not associated with variations of BMD and the fracture risk.

Endocrine Regulation on Bone by Thyroid

BACKGROUND

As an endocrine organ, the thyroid acts on the entire body by secreting a series of hormones, and bone is one of the main target organs of the thyroid.

SUMMARY

This review highlights the roles of thyroid hormones and thyroid diseases in bone homeostasis.

CONCLUSION

Thyroid hormones play significant roles in the growth and development of bone, and imbalance of thyroid hormones can impair bone homeostasis.

Inhibition of Metamorphosis, Thyroid Gland, and Skeletal Ossification Induced by Hexavalent Chromium in Bufo gargarizans Larvae

Hexavalent chromium (Cr [VI]) is one of the major detrimental heavy metal pollutants. In the present study, Bufo gargarizans were exposed to 0, 52, 104, 208, and 416 μg/L Cr (VI) from Gosner stage 2 until metamorphosis; and growth, development, and histological characteristics of the thyroid gland and skeletal ossification were examined. The results demonstrated that the survival rate of larvae exposed to Cr (VI) was not different from that measured in animals from the control group. However, high levels of Cr (VI) (104, 208, and 416 μg/L) were associated with significantly delayed growth and development. The suppression of skeletal ossification was observed at high Cr (VI) levels. Besides, histological alterations of the thyroid gland, such as follicular cell hyperplasia, colloid depletion, and peripheral colloid vacuolation, were found in 52 to 416 μg/L Cr (VI) treatments. The results of the present study highlight reductions in growth and development as well as percent metamorphosis and skeletal ossification due to histological alteration of the thyroid gland during exposure to Cr (VI) in B. gargarizans larvae. The present investigation could provide a basis for understanding the detrimental effects of Cr (VI) in amphibian larvae. Environ Toxicol Chem 2021;40:2474-2483. © 2021 SETAC.

Thyroid hormone and thyroid hormone nuclear receptors: History and present state of art

The present review traces the road leading to discovery of L-thyroxine, thyroid hormone (3,5,3´-triiodo-L-thyronine, T₃) and its cognate nuclear receptors. Thyroid hormone is a pleio-tropic regulator of growth, differentiation, and tissue homeostasis in higher organisms. The major site of the thyroid hormone action is predominantly a cell nucleus. T₃ specific binding sites in the cell nuclei have opened a new era in the field of the thyroid hormone receptors (TRs) discovery. T₃ actions are mediated by high affinity nuclear TRs, TRalpha and TRbeta, which function as T₃-activated transcription factors playing an essential role as transcription-modulating proteins affecting the transcriptional responses in target genes. Discovery and characterization of nuclear retinoid X receptors (RXRs), which form with TRs a heterodimer RXR/TR, positioned RXRs at the epicenter of molecular endocrinology. Transcriptional control via nuclear RXR/TR heterodimer represents a direct action of thyroid hormone. T₃ plays a crucial role in the development of brain, it exerts significant effects on the cardiovascular system, skeletal muscle contractile function, bone development and growth, both female and male reproductive systems, and skin. It plays an important role in maintaining the hepatic, kidney and intestine homeostasis and in pancreas, it stimulates the beta-cell proliferation and survival. The TRs cross-talk with other signaling pathways intensifies the T₃ action at cellular level. The role of thyroid hormone in human cancers, acting via its cognate nuclear receptors, has not been fully elucidated yet. This review is aimed to describe the history of T₃ receptors, starting from discovery of T3 binding sites in the cell nuclei to revelation of T₃ receptors as T₃-inducible transcription factors in relation to T₃ action at cellular level. It also focuses on milestones of investigation, comprising RXR/TR dimerization, cross-talk between T₃ receptors, and other regulatory pathways within the cell and mainly on genomic action of T₃. This review also focuses on novel directions of investigation on relationships between T₃ receptors and cancer. Based on the update of available literature and the author's experimental experience, it is devoted to clinicians and medical students.

Thyroid-stimulating hormone decreases the risk of osteoporosis by regulating osteoblast proliferation and differentiation

BACKGROUND

As the incidence of secretory osteoporosis has increased, bone loss, osteoporosis and their relationships with thyroid-stimulating hormone (TSH) have received increased attention. In this study, the role of TSH in bone metabolism and its possible underlying mechanisms were investigated.

METHODS

We analyzed the serum levels of free triiodothyronine (FT3), free thyroxine (FT4), and TSH and the bone mineral density (BMD) levels of 114 men with normal thyroid function. In addition, osteoblasts from rat calvarial samples were treated with different doses of TSH for different lengths of time. The related gene and protein expression levels were investigated.

RESULTS

A comparison of the BMD between the high-level and low-level serum TSH groups showed that the TSH serum concentration was positively correlated with BMD. TSH at concentrations of 10 mU/mL and 100 mU/mL significantly increased the mRNA levels of ALP, COI1 and Runx2 compared with those of the control (P < 0.05, P < 0.01). Bone morphogenetic protein (BMP)2 activity was enhanced with both increased TSH concentration and increased time. The protein levels of Runx2 and osterix were increased in a dose-dependent manner.

CONCLUSIONS

The circulating concentrations of TSH and BMD were positively correlated with normal thyroid function in males. TSH promoted osteoblast proliferation and differentiation in rat primary osteoblasts.

Vitamin K in Vertebrates' Reproduction: Further Puzzling Pieces of Evidence from Teleost Fish Species

Vitamin K (VK) is a fat-soluble vitamin that vertebrates have to acquire from the diet, since they are not able to de novo synthesize it. VK has been historically known to be required for the control of blood coagulation, and more recently, bone development and homeostasis. Our understanding of the VK metabolism and the VK-related molecular pathways has been also increased, and the two main VK-related pathways-the pregnane X receptor (PXR) transactivation and the co-factor role on the γ-glutamyl carboxylation of the VK dependent proteins-have been thoroughly investigated during the last decades. Although several studies evidenced how VK may have a broader VK biological function than previously thought, including the reproduction, little is known about the specific molecular pathways. In vertebrates, sex differentiation and gametogenesis are tightly regulated processes through a highly complex molecular, cellular and tissue crosstalk. Here, VK metabolism and related pathways, as well as how gametogenesis might be impacted by VK nutritional status, will be reviewed. Critical knowledge gaps and future perspectives on how the different VK-related pathways come into play on vertebrate's reproduction will be identified and proposed. The present review will pave the research progress to warrant a successful reproductive status through VK nutritional interventions as well as towards the establishment of reliable biomarkers for determining proper nutritional VK status in vertebrates.

Subclinical thyroid dysfunction, bone mineral density, and osteoporosis in a middle-aged Korean population

Thyroid dysfunction is associated with the loss of bone density (osteoporosis). However, the connection between subclinical thyroid dysfunction and osteoporosis remains controversial. This study found no apparent association between subclinical hypothyroidism or subclinical hyperthyroidism and bone mineral density (BMD) in the lumbar spine and femur.

INTRODUCTION

The present study examined the relationship between subclinical thyroid dysfunction and BMD in healthy middle-aged adults.

METHODS

A total of 25,510 healthy Koreans with normal free thyroxine levels were enrolled from January 2011 to December 2016, and 91% of subjects visited only once. The average age of the 15,761 women was 45, and the average age of the 9749 men was 48. Levels of thyroid-stimulating hormone (TSH) and BMD were recorded in all subjects. BMD was measured using dual-energy X-ray absorptiometry.

RESULTS

No apparent association was found between subclinical thyroid dysfunction and BMD in the lumbar spine, femur-neck, and proximal femur sites compared with a euthyroid group. Age, body mass index (BMI), and postmenopausal status affected BMD in women, and only BMI affected BMD in men. Subclinical hypothyroidism was independently associated with a lower risk of osteoporosis (odds ratio 0.657, 95% confidence interval 0.464-0.930) in 4710 postmenopausal women.

CONCLUSIONS

No apparent association was found between subclinical hypothyroidism or subclinical hyperthyroidism defined on single TSH measurement and BMD at the lumbar spine and femur in a large cohort of middle-aged men and women. Subclinical hypothyroidism was independently associated with a lower risk of osteoporosis in postmenopausal women.

Effects of Propranolol on Bone, White Adipose Tissue, and Bone Marrow Adipose Tissue in Mice Housed at Room Temperature or Thermoneutral Temperature

Growing female mice housed at room temperature (22°C) weigh the same but differ in body composition compared to mice housed at thermoneutrality (32°C). Specifically, mice housed at room temperature have lower levels of white adipose tissue (WAT). Additionally, bone marrow adipose tissue (bMAT) and cancellous bone volume fraction in distal femur metaphysis are lower in room temperature-housed mice. The metabolic changes induced by sub-thermoneutral housing are associated with lower leptin levels in serum and higher levels of Ucp1 gene expression in brown adipose tissue. Although the precise mechanisms mediating adaptation to sub-thermoneutral temperature stress remain to be elucidated, there is evidence that increased sympathetic nervous system activity acting via β-adrenergic receptors plays an important role. We therefore evaluated the effect of the non-specific β-blocker propranolol (primarily β₁ and β₂ antagonist) on body composition, femur microarchitecture, and bMAT in growing female C57BL/6 mice housed at either room temperature or thermoneutral temperature. As anticipated, cancellous bone volume fraction, WAT and bMAT were lower in mice housed at room temperature. Propranolol had small but significant effects on bone microarchitecture (increased trabecular number and decreased trabecular spacing), but did not attenuate premature bone loss induced by room temperature housing. In contrast, propranolol treatment prevented housing temperature-associated differences in WAT and bMAT. To gain additional insight, we evaluated a panel of genes in tibia, using an adipogenesis PCR array. Housing temperature and treatment with propranolol had exclusive as well as shared effects on gene expression. Of particular interest was the finding that room temperature housing reduced, whereas propranolol increased, expression of the gene for acetyl-CoA carboxylase (Acacb), the rate-limiting step for fatty acid synthesis and a key regulator of β-oxidation. Taken together, these findings provide evidence that increased activation of β₁ and/or β₂ receptors contributes to reduced bMAT by regulating adipocyte metabolism, but that this pathway is unlikely to be responsible for premature cancellous bone loss in room temperature-housed mice.

Thermoneutral housing attenuates premature cancellous bone loss in male C57BL/6J mice

Mice are a commonly used model to investigate aging-related bone loss but, in contrast to humans, mice exhibit cancellous bone loss prior to skeletal maturity. The mechanisms mediating premature bone loss are not well established. However, our previous work in female mice suggests housing temperature is a critical factor. Premature cancellous bone loss was prevented in female C57BL/6J mice by housing the animals at thermoneutral temperature (where basal rate of energy production is at equilibrium with heat loss). In the present study, we determined if the protective effects of thermoneutral housing extend to males. Male C57BL/6J mice were housed at standard room temperature (22°C) or thermoneutral (32°C) conditions from 5 (rapidly growing) to 16 (slowly growing) weeks of age. Mice housed at room temperature exhibited reductions in cancellous bone volume fraction in distal femur metaphysis and fifth lumbar vertebra; these effects were abolished at thermoneutral conditions. Mice housed at thermoneutral temperature had higher levels of bone formation in distal femur (based on histomorphometry) and globally (serum osteocalcin), and lower global levels of bone resorption (serum C-terminal telopeptide of type I collagen) compared to mice housed at room temperature. Thermoneutral housing had no impact on bone marrow adiposity but resulted in higher abdominal white adipose tissue and serum leptin. The overall magnitude of room temperature housing-induced cancellous bone loss did not differ between male (current study) and female (published data) mice. These findings highlight housing temperature as a critical experimental variable in studies using mice of either sex to investigate aging-related changes in bone metabolism.

Thyroid hormone modulation during zebrafish development recapitulates evolved diversity in danionin jaw protrusion mechanics

Protrusile jaws are a highly useful innovation that has been linked to extensive diversification in fish feeding ecology. Jaw protrusion can enhance the performance of multiple functions, such as suction production and capturing elusive prey. Identifying the developmental factors that alter protrusion ability will improve our understanding of fish diversification. In the zebrafish protrusion arises postmetamorphosis. Fish metamorphosis typically includes significant changes in trophic morphology, accompanies a shift in feeding niche and coincides with increased thyroid hormone production. We tested whether thyroid hormone affects the development of zebrafish feeding mechanics. We found that it affected all developmental stages examined, but that effects were most pronounced after metamorphosis. Thyroid hormone levels affected the development of jaw morphology, feeding mechanics, shape variation, and cranial ossification. Adult zebrafish utilize protrusile jaws, but an absence of thyroid hormone impaired development of the premaxillary bone, which is critical to jaw protrusion. Premaxillae from early juvenile zebrafish and hypothyroid adult zebrafish resemble those from adults in the genera Danionella, Devario, and Microdevario that show little to no jaw protrusion. Our findings suggest that evolutionary changes in how the developing skulls of danionin minnows respond to thyroid hormone may have promoted diversification into different feeding niches.

Wnt3a downregulates thyroid hormone-induced osteocalcin expression in osteoblasts

Wnt3a is a crucial modulator of bone metabolism through the canonical Wnt/β-catenin signaling pathway in bone-forming osteoblasts. We previously reported that the expression of osteocalcin is stimulated by triiodothyronine (T₃) at least in part through the activation of p38 mitogen-activated protein (MAP) kinase but not p44/p42 MAP kinase in osteoblast-like MC3T3-E1 cells. In the present study, we investigated the effect of Wnt3a on the T₃-induced osteocalcin expression in these cells. Wnt3a suppressed the release of osteocalcin induced by T₃. The inhibitory effect of Wnt3a was dose-dependent between 0.3 and 30 ng/ml. SB216763, an inhibitor of glycogen synthase kinase-3β, that reduces the phosphorylation of β-catenin, inhibited the T₃-induced osteocalcin release. Wnt3a, as well as SB216763, reduced the expression of osteocalcin mRNA induced by T₃. The transcriptional activity induced by T₃, assessed by a luciferase activity, was also suppressed by both Wnt3a and SB216763. In contrast, Wnt3a did not markedly affect the T₃-stimulated phosphorylation of p38 MAP kinase. These results suggested that Wnt3a downregulates the T₃-stimulated osteocalcin expression in MC3T3-E1 cells, and the suppressive effect of Wnt3a is independent of p38 MAP kinase.

Paradigms of Dynamic Control of Thyroid Hormone Signaling

Thyroid hormone (TH) molecules enter cells via membrane transporters and, depending on the cell type, can be activated (i.e., T4 to T3 conversion) or inactivated (i.e., T3 to 3,3'-diiodo-l-thyronine or T4 to reverse T3 conversion). These reactions are catalyzed by the deiodinases. The biologically active hormone, T3, eventually binds to intracellular TH receptors (TRs), TRα and TRβ, and initiate TH signaling, that is, regulation of target genes and other metabolic pathways. At least three families of transmembrane transporters, MCT, OATP, and LAT, facilitate the entry of TH into cells, which follow the gradient of free hormone between the extracellular fluid and the cytoplasm. Inactivation or marked downregulation of TH transporters can dampen TH signaling. At the same time, dynamic modifications in the expression or activity of TRs and transcriptional coregulators can affect positively or negatively the intensity of TH signaling. However, the deiodinases are the element that provides greatest amplitude in dynamic control of TH signaling. Cells that express the activating deiodinase DIO2 can rapidly enhance TH signaling due to intracellular buildup of T3. In contrast, TH signaling is dampened in cells that express the inactivating deiodinase DIO3. This explains how THs can regulate pathways in development, metabolism, and growth, despite rather stable levels in the circulation. As a consequence, TH signaling is unique for each cell (tissue or organ), depending on circulating TH levels and on the exclusive blend of transporters, deiodinases, and TRs present in each cell. In this review we explore the key mechanisms underlying customization of TH signaling during development, in health and in disease states.

The effect of suppressive thyroxine therapy in nodular goiter in postmenopausal women and 2 year's bone mineral density change

The efficacy of thyroxine suppressive therapy in reducing nodular growth and its effect to bone mineral density (BMD) in postmenopausal women is still debated. This study aimed to evaluate the therapeutic effect of thyroxine and its influence on BMD. Postmenopausal women with nodular or multinodular goiter during 2013-2015 at Chang Gung Memorial Hospital were enrolled and retrospectively traced back to the first date of visit or treatment. Ninety-four eligible patients were enrolled, of whom 45 were thyroxine-treated (LT-4 group) and 49 were treatment-naïve (control group). Data, including volume of nodules, were analyzed retrospectively. BMD was measured in each LT-4 group patient since the year of enrollment. Nodular volumes were reduced in both LT-4 (from 4.89 ± 4.46 to 4.10 ± 4.57 mL, p = 0.033) and control group (3.48 ± 4.36 to 3.09 ± 2.88 mL, p = 0.239) at initial 2-year follow-up. Nodular volume in LT-4 group increased insignificantly (from 4.89 ± 4.46 to 4.91 ± 5.40 mL, p = 0.711) at the end of 7-year follow-up. The best cut-off predictive nodular volume that may have responded to thyroxine is 2.6 mL (AUC, 0.740; sensitivity, 0.750; specificity, 0.733) during first 2 year. Lumbar spine, total hip and femoral neck BMD were not significantly changed during 2 year's thyroxine suppression therapy. In conclusion, thyroxine suppressive therapy in postmenopausal women had significant reduction in nodule volume at initial 2 years of treatment, especially in volume larger than 2.6 mL. Prolonged thyroxine treatment did not benefit nodular size reduction and may affect BMD minimally in postmenopausal women.

The Association of Thyroid Function With Bone Density During Childhood

CONTEXT

Although the skeleton is a well-known thyroid hormone target organ, very little data are available on the association of thyroid function with bone outcomes during childhood.

OBJECTIVE

To study the association of thyroid function with bone mass during childhood.

DESIGN, SETTING, AND PARTICIPANTS

Population-based prospective cohort including 4204 children with TSH and free T4 (FT4) measured at the age of 6 years.

MAIN OUTCOME MEASURES

Bone density was assessed by a total body dual-energy X-ray absorptiometry scan at the median age of 6 years (95% range, 5.6 to 7.9) and at the age of 10 years (95% range, 9.0 to 10.9) in 4204 and 3404 participants, respectively.

RESULTS

There was an inverse association of TSH with bone mineral density (BMD) at the age of 6 (β -0.028 ± 0.011, P = 0.009) and with follow-up measurements at the age of 10 (β -0.027 ± 0.011, P = 0.014), but not with bone mineral content (BMC) at the age of 6 (β -0.028 ± 0.015, P = 0.06) or for follow-up measurements of BMC at the age of 10 (β -0.011 ± 0.015, P = 0.47). There was an inverse association of FT4 with BMD (β -0.016 ± 0.006, P = 0.014) and BMC (β -0.023 ± 0.009, P = 0.009) cross-sectionally, and also at the age of 10 years (BMD: β -0.018 ± 0.007, P = 0.007; BMC: β -0.021 ± 0.009, P = 0.020).

CONCLUSION

A higher FT4 concentration is associated with lower bone mass at the age of 6 and at the age of 10 years. These data provide insights into the effects of thyroid function on bone physiology during childhood.

Differences in the auxological characters of children with short stature - Differential diagnostic possibilities of hypothyreosis

This study aimed to define the differences in growth characteristics in the three most frequent causes of growth retardation - growth hormone deficiency, hypothyreosis and constitutional delay of growth and development - in order to provide diagnostic means for distinguishing these disorders. The study included 166 children with growth disorders aged 4-18 years. The height for age, the bone age using the TW3 method, the predicted height as the target height and the current prediction using the TW3 method were studied. For bone age, the radius, ulna and short bones compartment (RUS) and carpal bones (CARP) were evaluated separately and the difference in their delay in relation to chronological age (ΔBA_RUS_CARP) was determined. The relationship of the studied variables with sex and the underlying diagnosis was tested and the relationship of hypothyreosis and growth data was estimated. The model was tested on the growth data of 104 randomly selected patients with a growth disorder. The largest significant distinction was demonstrated by the difference ΔBA_RUS_CARP in hypothyreosis. The created linear regression model was highly statistically significant (χ² = 19.4, p < 0.0001) and showed high selectivity (0.609, 95% CI 0.409; 0.808) as well as high specificity (0.864, 95% CI 0.781; 0.946). The clinical validity of the model demonstrated a 61% predictive value for the detection and an 81% successful specification of hypothyreosis. The study demonstrated the possibility of distinguishing suspected hypothyreosis from other causes of growth retardation based on differences in severity of the ossification delay in skeletal compartments of the hand.

TSH-receptor antibodies may prevent bone loss in pre- and postmenopausal women with Graves' disease and Graves' orbitopathy

OBJECTIVE

Thyrotoxicosis is established risk factor for osteoporosis due to increased bone turnover. Glucocorticoids often administered for Graves' orbitopathy (GO) have additional negative effect on bone mineral density (BMD). Our aim was to examine the influence of thyroid hormones, TSH, TSH-receptor antibodies (TRAb) and glucocorticoid treatment on bone in women with Graves' thyrotoxicosis and Graves' orbitopathy (GO).

SUBJECTS AND METHODS

Forty seven women with Graves' disease, mean age 55.6 ± 12.8 (23 women with thyrotoxicosis and 24 hyperthyroid with concomitant GO and glucocorticoid therapy) and 40 age-matched healthy female controls were enrolled in the study. We analyzed clinical features, TSH, FT4, FT3, TRAb, TPO antibodies. BMD of lumbar spine and hip was measured by DEXA and 10-year fracture risk was calculated with FRAX tool.

RESULTS

The study showed significantly lower spine and femoral BMD (g/cm2) in patients with and without GO compared to controls, as well as significantly higher fracture risk. Comparison between hyperthyroid patients without and with orbitopathy found out significantly lower spine BMD in the first group (p = 0.0049). Negative correlations between FT3 and femoral neck BMD (p = 0.0001), between FT4 and BMD (p = 0.049) and positive between TSH and BMD (p = 0.0001), TRAb and BMD (p = 0.026) were observed. Fracture risk for major fractures and TRAb were negatively associated (p = 0.05). We found negative correlation of BMD to duration of thyrotoxicosis and cumulative steroid dose.

CONCLUSIONS

Our results confirm the negative effect of hyperthyroid status on BMD. TRAb, often in high titers in patients with GO, may have protective role for the bone, but further research is needed.

Fish as a model to assess chemical toxicity in bone

Environmental toxicology has been expanding as growing concerns on the impact of produced and released chemical compounds over the environment and human health are being demonstrated. Among the toxic effects observed in organisms exposed to pollutants, those affecting skeletal tissues (osteotoxicity) have been somehow overlooked in comparison to hepato-, immune-, neuro- and/or reproductive toxicities. Nevertheless, sub-lethal effects of toxicants on skeletal development and/or bone maintenance may result in impaired growth, reduced survival rate, increased disease susceptibility and diminished welfare. Osteotoxicity may occur by acute or chronic exposure to different environmental insults. Because of biologically and technically advantagous features - easy to breed and inexpensive to maintain, external and rapid rate of development, translucent larvae and the availability of molecular and genetic tools - the zebrafish (Danio rerio) has emerged in the last decade as a vertebrate model system of choice to evaluate osteotoxicity. Different experimental approaches in fish species and analytical tools have been applied, from in vitro to in vivo systems, from specific to high throughput methodologies. Current knowledge on osteotoxicity and underlying mechanisms gained using fish, with a special emphasis on zebrafish systems, is reviewed here. Osteotoxicants have been classified into four categories according to the pathway involved in the transduction of the osteotoxic effects: activation/inhibition of membrane and/or nuclear receptors, alteration of redox condition, mimicking of bone constituents and unknown pathways. Knowledge on these pathways is also reported here as it may provide critical insights into the development, production and release of future chemical compounds with none or low osteotoxicity, thus promoting the green/environmental friendly chemistry.

Reference and Influential Factors of Serum Bone Markers in Chinese Adolescents

This study aimed to establish reference ranges of bone markers in Chinese adolescents between the age of 12 and 16, and to search these markers’ characteristics and influential factors. Personal information and fasting blood samples were collected from 174 healthy adolescents in Northeast China. Serum levels of PINP, ALP, β-CrossLaps, calcium, phosphate, PTH, 25(OH)D and TSH were measured. Reference ranges were established for PINP [(85.55–2,028.75)ng/ml], ALP [(53.88–463.63)U/L], β-CrossLaps [(0.16–1.19)ng/ml], calcium [(2.35–2.70)mmol/L], phosphate [(1.17–2.06)mmol/L] and PTH [(2.64–43.36)μg/L] in this population. We observed that bone formation markers PINP and ALP levels were evidently higher when compared to kit references for adults. Reference ranges for calcium, phosphate and PTH also differed from those provided by kit manuals. Serum ALP, PINP, phosphate and PTH changed with age (all P < 0.005), and were significantly higher in boys than in girls (all P < 0.05). Serum 25(OH)D and TSH levels didn’t correlate with PINP, ALP and β-CrossLaps (all P > 0.05). In conclusion, unique reference ranges should be provided for adolescents. BMI, sex and age independently influence certain serum bone markers in adolescents. Vitamin D deficiency is widespread. Serum levels of vitamin D and TSH may not influence bone turnover markers in this population.

Thyroid hormone analogs for the treatment of dyslipidemia: past, present, and future

OBJECTIVE

Treatment of dyslipidemia is a major burden for public health. Thyroid hormone regulates lipid metabolism by binding the thyroid hormone receptor (TR), but the use of thyroid hormone to treat dyslipidemia is not indicated due to its deleterious effects on heart, bone, and muscle. Thyroid hormone analogs have been conceived to selectively activate TR in the liver, thus reducing potential side-effects.

METHODS

The authors searched the PubMed database to review TR and the action of thyromimetics in vitro and in animal models. Then, all double-blind, placebo controlled trials that analyzed the use of thyroid hormone analog for the treatment of dyslipidemia in humans were included. Finally, the ongoing research on the use of TR agonists was searched, searching the US National Institutes of Health Registry and the WHO International Clinical Trial Registry Platform (ICTRP).

RESULTS

Thyromimetics were tested in humans for the treatment of dyslipidemia, as a single therapeutic agent or as an add-on therapy to the traditional lipid-lowering drugs. In most trials, thyromimetics lowered total cholesterol, low-density lipoprotein cholesterol, and triglycerides, but their use has been associated with adverse side-effects, both in pre-clinical studies and in humans.

CONCLUSIONS

The use of thyromimetics for the treatment of dyslipidemia is not presently recommended. Future possible clinical applications might include their use to promote weight reduction. Thyromimetics might also represent an interesting alternative, both for the treatment of non-alcoholic steatohepatitis, and type 2 diabetes due to their positive effects on insulin sensitivity. Finally, additional experimental and clinical studies are needed for a better comprehension of the effect(s) of a long-term therapy.

Effects of Bone Marrow Mesenchymal Stem Cells-Conditioned Medium on Tibial Partial Osteotomy Model of Fracture Healing in Hypothyroidism Rats

Background

Hypothyroidism is associated with dysfunction of the bone turnover with reduced osteoblastic bone formation and osteoclastic bone resorption. Mesenchyme stem cells (MSCs) secrete various factors and cytokines that may stimulate bone regeneration. The aim of this study was to determine the effects of MSCs-conditioned medium (CM) in hypothyroidism male rats after inducing bone defect.

Methods

: In this study, 24 male rats were randomly assigned to three groups: (I) hypothyroidism+bone defect (HYPO), (II) hypothyroidism+bone defect+CM (HYPO+CM), and (III) no hypothyroidism+bone defect (control). Four weeks after surgery, the right tibia was removed, and immediately, biomechanical and histological examinations were performed.

Results

The results showed a significant reduction in bending stiffness (32.64±3.99), maximum force (14.63±1.89), high stress load (7.59±2.31), and energy absorption (12.68±2.12) at the osteotomy site in hypothyroidism rats in comparison to the control and hypothyroidism+condition medium groups (P<0.05). There was also a significant decrease in the trabecular bone volume (3.86±3.88) and the number of osteocytes (5800±859.8) at the osteotomy site in hypothyroidism rats compared to the control and hypothyroidism+condition medium groups (P<0.01 and P<0.02, respectively).

Conclusion

The present study suggests that the use of the CM can improve the fracture regeneration and accelerates bone healing at the osteotomy site in hypothyroidism rats.

Vitamin A Affects Flatfish Development in a Thyroid Hormone Signaling and Metamorphic Stage Dependent Manner

Vitamin A (VA) and retinoid derivatives are known morphogens controlling vertebrate development. Despite the research effort conducted during the last decade, the precise mechanism of how VA induces post-natal bone changes, and particularly those operating through crosstalk with the thyroid hormones (THs) remain to be fully understood. Since effects and mechanisms seem to be dose and time-dependent, flatfish are an interesting study model as they undergo a characteristic process of metamorphosis driven by THs that can be followed by external appearance. Here, we studied the effects of VA imbalance that might determine Senegalese sole (Solea senegalensis) skeletogenetic phenotype through development of thyroid follicles, THs homeostasis and signaling when a dietary VA excess was specifically provided during pre-, pro- or post-metamorphic stages using enriched rotifers and Artemia as carriers. The increased VA content in enriched live prey was associated to a higher VA content in fish at all developmental stages. Dietary VA content clearly affected thyroid follicle development, T3 and T4 immunoreactive staining, skeletogenesis and mineralization in a dose and time-dependent fashion. Gene expression analysis showed that VA levels modified the mRNA abundance of VA- and TH-specific nuclear receptors at specific developmental stages. Present results provide new and key knowledge to better understand how VA and TH pathways interact at tissue, cellular and nuclear level at different developmental periods in Senegalese sole, unveiling how dietary modulation might determine juvenile phenotype and physiology.

Resveratrol suppresses thyroid hormone‑induced osteocalcin synthesis in osteoblasts

Resveratrol, a polyphenolic compound that is present in grape skins, berries and red wine, may be beneficial for human health through its anti‑inflammatory and anti‑oxidant effects. It has been previously demonstrated that resveratrol exerts its biological effects primarily via sirtuin 1 (SIRT1) activation. We previously reported that triiodothyronine (T3) induces osteocalcin synthesis in osteoblast‑like MC3T3‑E1 cells, and that p38 mitogen‑activated protein (MAP) kinase mediates the T3‑stimulated synthesis of osteocalcin. The present study investigated the effect of resveratrol on T3‑induced osteocalcin synthesis and its underlying mechanism in MC3T3‑E1 cells. Cultured cells were stimulated with T3, and osteocalcin release from MC3T3‑E1 cells was measured by ELISA and phosphorylation of p38 MAP kinase was analyzed by western blotting. Resveratrol significantly suppressed the release of osteocalcin stimulated by T3, and SRT1720, a SIRT1 activator, significantly reduced T3‑induced osteocalcin release. The expression level of osteocalcin mRNA stimulated by T3 was significantly attenuated by resveratrol and T3‑induced transactivation activity of the thyroid hormone‑responsive element was significantly diminished by resveratrol. However, only limited effects of resveratrol on the T3‑induced phosphorylation of p38 MAP kinase were observed. The results of the present study demonstrated that resveratrol suppresses T3‑stimulated osteocalcin synthesis at a point upstream of transcription in osteoblasts, and that the inhibitory effect of resveratrol is mediated, at least partially, through SIRT1 activation. These results indicate that there may be a novel role for the polyphenol in the modulation of bone metabolism.

Congenital Hypothyroidism and Bone Remodeling Cycle

OBJECTIVE

The present study aimed to evaluate the biochemical markers of bone turnover in children with congenital hypothyroidism during the course of treatment as compared to healthy children selected as controls.

METHODS

The study included 31 children with congenital hypothyroidism and 29 healthy children. In both groups, we evaluated serum procollagen type-1 N-terminal propeptide (PINP) and tartrate-resistant acid phosphatase type 5b isoform (TRACP 5b) levels as bone turnover markers.

RESULTS

In both groups, thyroid hormone levels were within normal limits. The levels of vitamin D were significantly higher in the cases with congenital hypothyroidism. Although PINP levels were not found to be different, TRACP 5b levels which are related to osteoclastic activities were significantly higher in the control group.

CONCLUSION

We did not detect an increase in bone resorption in patients with congenital hypothyroidism, despite long-term treatment with LT4. Our results suggest that with effective vitamin D treatment and thyroxin replacement, congenital hypothyroidism is not a deleterious factor for bone turnover.

Physiological Bone Remodeling: Systemic Regulation and Growth Factor Involvement

Bone remodeling is essential for adult bone homeostasis. It comprises two phases: bone formation and resorption. The balance between the two phases is crucial for sustaining bone mass and systemic mineral homeostasis. This review highlights recent work on physiological bone remodeling and discusses our knowledge of how systemic and growth factors regulate this process.

Subclinical hypothyroidism in childhood - current knowledge and open issues

Subclinical hypothyroidism is defined as serum levels of TSH above the upper limit of the reference range, in the presence of normal concentrations of total T₄ or free T₄. This biochemical profile might be an indication of mild hypothyroidism, with a potential increased risk of metabolic abnormalities and cardiovascular disease recorded among adults. Whether subclinical hypothyroidism results in adverse health outcomes among children is a matter of debate and so management of this condition remains challenging. Mild forms of untreated subclinical hypothyroidism do not seem to be associated with impairments in growth, bone health or neurocognitive outcome. However, ongoing scientific investigations have highlighted the presence of subtle proatherogenic abnormalities among children with modest elevations in their TSH levels. Although current findings are insufficient to recommend levothyroxine treatment for all children with mild asymptomatic forms of subclinical hypothyroidism, they highlight the potential need for assessment of cardiovascular risk among children with this condition. Increased understanding of the early metabolic risk factors associated with subclinical hypothyroidism in childhood will help to improve the management of affected individuals.

Low Normal TSH levels are Associated with Impaired BMD and Hip Geometry in the Elderly

Subclinical hyperthyroidism is known to be associated with the risk of fractures in elderly people. However, there are few studies assessing whether low normal thyroid-stimulating hormone (TSH) levels affect bone density and geometry. Here, we aimed to assess the influence of the TSH level on bone mineral density (BMD) and geometry in elderly euthyroid subjects. This was a cross-sectional cohort study. A total of 343 men and 674 women with euthyroidism were included and analyzed separately. The subjects were divided into tertiles based on the serum TSH level. The BMD and geometry were measured using dual-energy X-ray absorptiometry and a hip structural analysis program. Multiple regression analysis was used to compute the odds ratios of osteoporosis in the lower TSH tertile group and the association between geometry parameters and the TSH level. We found that the femoral neck and total hip BMDs were lower in the lower TSH tertile group. In women, the cross-sectional area and cortical thickness of the femur were negatively associated with the TSH level in all three regions (the narrow neck, intertrochanter, and femoral shaft); however, in men, these geometry parameters were significantly associated with the TSH level only in the intertrochanter region. The buckling ratio, a bone geometry parameter representing cortical instability, was significantly higher in the lower TSH tertile group in all three regions in women, but not in men. Our results indicated that lower TSH levels in the euthyroid range are related to lower BMD and weaker femoral structure in elderly women.

Attenuation by incretins of thyroid hormone-stimulated osteocalcin synthesis in osteoblasts

Incretins, the polypeptide hormone glucose- dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) secreted from the small intestine after nutrient ingestion, are generally known to stimulate insulin secretion from pancreatic β-cells. We previously demonstrated that triiodothyronine (T₃) stimulates osteocalcin synthesis at least in part through p38 mitogen-activated protein kinase in osteoblast-like MC3T3-E1 cells. In the present study, we investigated the effects of GIP and GLP-1 on T₃-stimulated osteocalcin synthesis and the mechanism of action involved in MC3T3-E1 cells. GIP and GLP-1 markedly suppressed the T₃-stimulated osteocalcin release. GIP and GLP-1 significantly attenuated the expression levels of osteocalcin mRNA induced by T₃. The T₃-stimulated transactivation activity of the thyroid hormone-responsive element was reduced by GIP and GLP-1. These results suggest that incretins repressed the T₃-stimulated osteocalcin synthesis in osteoblast-like MC3T3-E1 cells, and the suppressive effect of incretins was mediated through transcriptional levels.

Impaired skeletal health in patients with chronic atrophic gastritis

OBJECTIVE

In chronic atrophic gastritis (CAG), destruction of gastric parietal cells causes anacidity and hypergastrinemia. Use of proton pump inhibitors, which also induces gastric anacidity, is associated with increased fracture rates. Our objectives were to study possible differences in bone mineral density (BMD) and bone quality in patients with CAG compared to controls.

MATERIAL AND METHODS

We performed a cross-sectional study on 17 CAG patients aged 54 ± 13 years and 41 sex- and age-matched controls. Lumbar and femoral BMD and bone quality assessed by lumbar trabecular bone score (TBS) were measured by DXA, and bone material strength (BMS) by microindentation of the tibia. Serum bone markers (CTX, P1NP, sclerostin, osteocalcin, OPG, RANKL) were analyzed.

RESULTS

We found lower lumbar BMD Z-score (-0.324 ± 1.096 versus 0.456 ± 1.262, p = 0.030), as well as a higher frequency of osteoporosis at the lumbar spine (p = 0.046) and osteopenia at total hip (p = 0.019) in patients compared to controls. In a post hoc subgroup analysis, we observed that the differences were confined to the male patients. TBS also tended to be lower in male patients (p = 0.059), while BMS did not differ between the groups. Osteocalcin, sclerostin, OPG, and OPG/RANKL ratio were lower in patients compared to controls, while CTX and P1NP did not differ between the groups.

CONCLUSIONS

We observed lower lumbar BMD, increased frequency of osteopenia and osteoporosis in male, but not female patients with CAG. Bone markers suggest a decrease in bone formation and increased bone resorption in CAG patients compared to controls.

Changes in bone mineral density and trabecular bone score in Graves' disease patients after anti-thyroid therapy

Objective

The purpose of this study was to evaluate changes in bone quantity based on bone mineral density (BMD) and bone quality based on trabecular bone score (TBS) in Graves' disease patients after anti-thyroid therapy.

Research design and method

This retrospective study included premenopausal female and male patients with Graves' disease who received BMD measurement more than two times during treatment. BMD and thyroid function tests with free thyroxine (FT4), total triiodothyronine (T3), thyroid stimulating hormone (TSH), and TSH receptor antibody (TRAb) levels were collected two times during follow-up. TBS was calculated using TBS insight^® software (version 2.1) from dual-energy X-ray absorptiometry images.

Results

Thirty Graves' disease patients (17 males, 56%; 13 premenopausal females, 44%) with a mean age of 35.3 ± 9.9 years were included. The mean follow-up period was 20.7 ± 8.5 months. The median levels of FT4, TSH and TRAb improved at follow-up [2.55 ng/dL (Interquartile range (IQR) 2.07–3.78) to 1.28 ng/dL (IQR 1.23–1.39), 0.015 mIU/L (IQR 0.01–0.04) to 0.89 mIU/L (IQR 0.35–1.55), 17.0 IU/L (IQR 5.0–40.3) to 5.0 IU/L (5.0–6.0), respectively; p < 0.001]. Median BMD (lumbar spine) values also improved from 1.118 g/cm² (IQR 1.000–1.119) to 1.167 g/cm² (IQR 1.050–1.219) (p = 0.001) at follow-up. TBS increased from 1.377 (IQR 1.299–1.422) to 1.390 (IQR 1.327–1.430) after treatment (p = 0.038).

Conclusion

Both bone quality and density improved after anti-thyroid treatment in premenopausal female and male Graves' disease patients.

Thyroid hormone receptor-β1 signaling is critically involved in regulating secondary ossification via promoting transcription of the Ihh gene in the epiphysis

Thyroid hormone (TH) action is mediated through two nuclear TH receptors, THRα and THRβ. Although the role of THRα is well established in bone, less is known about the relevance of THRβ-mediated signaling in bone development. On ther basis of our recent finding that TH signaling is essential for initiation and formation of secondary ossification center, we evaluated the role of THRs in mediating TH effects on epiphysial bone formation. Two-day treatment of TH-deficient Tshr(-/-) mice with TH increased THRβ1 mRNA level 3.4-fold at day 7 but had no effect on THRα1 mRNA level at the proximal tibia epiphysis. Treatment of serum-free cultures of tibias from 3-day-old mice with T3 increased THRβ1 expression 2.1- and 13-fold, respectively, at 24 and 72 h. Ten-day treatment of Tshr(-/-) newborns (days 5-14) with THRβ1 agonist GC1 at 0.2 or 2.0 μg/day increased BV/TV at day 21 by 225 and 263%, respectively, compared with vehicle treatment. Two-day treatment with GC1 (0.2 μg/day) increased expression levels of Indian hedgehog (Ihh) 100-fold, osterix 15-fold, and osteocalcin 59-fold compared with vehicle at day 7 in the proximal tibia epiphysis. Gel mobility shift assay demonstrated that a putative TH response element in the distal promoter of mouse Ihh gene interacted with THRβ1. GC1 treatment (1 nM) increased Ihh distal promoter activity 20-fold after 48 h in chondroctyes. Our data suggest a novel role for THRβ1 in secondary ossification at the epiphysis that involves transcriptional upregulation of Ihh gene.

Reduced bone mineral density in glycogen storage disease type III: evidence for a possible connection between metabolic imbalance and bone homeostasis

INTRODUCTION

Glycogen storage disease type III (GSDIII) is an inborn error of carbohydrate metabolism caused by deficient activity of glycogen debranching enzyme (GDE). It is characterized by liver, cardiac muscle and skeletal muscle involvement. The presence of systemic complications such as growth retardation, ovarian polycystosis, diabetes mellitus and osteopenia/osteoporosis has been reported. The pathogenesis of osteopenia/osteoporosis is still unclear.

OBJECTIVES

The aim of the current study was to evaluate the bone mineral density (BMD) in GSDIII patients and the role of metabolic and endocrine factors and physical activity on bone status.

METHODS

Nine GSDIII patients were enrolled (age 2-20years) and compared to eighteen age and sex matched controls. BMD was evaluated by Dual-emission-X-ray absorptiometry (DXA) and Quantitative ultrasound (QUS). Clinical and biochemical parameters of endocrine system function and bone metabolism were analyzed. Serum levels of the metabolic control markers were evaluated. Physical activity was evaluated by administering the International Physical Activity Questionnaire (IPAQ).

RESULTS

GSDIII patients showed reduced BMD detected at both DXA and QUS, decreased serum levels of IGF-1, free IGF-1, insulin, calcitonin, osteocalcin (OC) and increased serum levels of C-terminal cross-linking telopeptide of type I collagen (CTX). IGF-1 serum levels inversely correlated with AST and ALT serum levels. DXA Z-score inversely correlated with cholesterol and triglycerides serum levels and directly correlated with IGF-1/IGFBP3 molar ratio. No difference in physical activity was observed between GSDIII patients and controls.

DISCUSSION

Our data confirm the presence of reduced BMD in GSDIII. On the basis of the results, we hypothesized that metabolic imbalance could be the key factor leading to osteopenia, acting through different mechanisms: chronic hyperlipidemia, reduced IGF-1, Insulin and OC serum levels. Thus, the mechanism of osteopenia/osteoporosis in GSDIII is probably multifactorial and we speculate on the factors involved in its pathogenesis.

Slipped capital femoral epiphysis and associated hypothyroidism. A review of the literature with two classic case examples

Slipped capital femoral epiphysis (SCFE) is a relatively common hip disorder often seen in overweight, peripubertal children. Although the exact etiology is uncertain, it is generally accepted that underlying endocrinopathies play a role in the pathogenesis. Hypothyroidism is the endocrine disorder cited most commonly in association with SCFE, and patients often have no history of thyroid dysfunction at the time of presentation. Despite being a well-recognized risk factor, recommendations for screening thyroid function in patients with typical presentations of SCFE have not been deemed cost-effective; however, there is data to support screening for hypothyroidism in patients with atypical presentations of SCFE or short stature. Hypothyroidism may have a significant impact on healing and bone union after surgical management of SCFE and there is a paucity of case reports in the literature describing potential peri- and postoperative complications. We performed a systematic review of the literature of all reported cases of SCFE with associated hypothyroidism using the search terms, which demonstrated a physiologic relationship between hypothyroidism and SCFE. Two case reports of SCFE in patients with hypothyroidism and associated complications are presented with the literature review. There is a physiologic relationship between thyroid dysfunction and SCFE, and we postulate that profound hypothyroidism may contribute to delayed healing or nonunion in patients undergoing operative management. We support the recommendation to screen patients with short stature, atypical presentation of SCFE, or perisistent nonunion after surgery. In cases of hypothyroidism, we recommend thyroid hormone replacement and laboratory confirmation of return to euthyroid state prior to operative intervention.

Thyrotropin serum levels are differentially associated with biochemical markers of bone turnover and stiffness in women and men: results from the SHIP cohorts

In two large German population-based cohorts, we showed positive associations between serum thyrotropin (TSH) concentrations and the Fracture Risk Assessment score (FRAX) in men and positive associations between TSH concentrations and bone turnover markers in women.

INTRODUCTION

The role of thyroid hormones on bone stiffness and turnover is poorly defined. Existing studies are confounded by differences in design and small sample size. We assessed the association between TSH serum concentrations and bone stiffness and turnover in the SHIP cohorts, which are two population-based cohorts from a region in Northern Germany comprising 2654 men and women and 3261 men and women, respectively.

METHODS

We calculated the bone stiffness index using quantitative ultrasound (QUS) at the calcaneus, employed FRAX score for assessment of major osteoporotic fractures, and measured bone turnover markers, N-terminal propeptide of type I procollagen (P1NP), bone-specific alkaline phosphatase (BAP), osteocalcin, and type I collagen cross-linked C-telopeptide (CTX) in all subjects and sclerostin in a representative subgroup.

RESULTS

There was no association between TSH concentrations and the stiffness index in both genders. In men, TSH correlated positively with the FRAX score both over the whole TSH range (p < 0.01) and within the reference TSH range (p < 0.01). There were positive associations between TSH concentrations and P1NP, BAP, osteocalcin, and CTX (p < 0.01) in women but not in men. There was no significant association between TSH and sclerostin levels.

CONCLUSIONS

TSH serum concentrations are associated with gender-specific changes in bone turnover and stiffness.

Relationship of anthropometric measurements to thyroid nodules in a Chinese population

OBJECTIVE

Previous studies have found that overweight and obesity are related to numerous diseases, including thyroid cancer and thyroid volume. This study evaluates the relationship between body size and the presence of thyroid nodules in a Chinese population.

METHODS

A total of 6793 adults and 2410 children who underwent thyroid ultrasonography were recruited in this cross-sectional study in Hangzhou, Zhejiang Province, China, from March to October, 2010. Sociodemographic characteristics and potential risk factors of thyroid nodules were collected by questionnaire. Height and weight were measured using standard protocols. Associations of height, weight, body mass index (BMI) and body surface area (BSA) with the presence of thyroid nodules were evaluated using multiple logistic regression models.

RESULTS

After adjustment for potential risk factors, an increased risk of thyroid nodule incidence was associated with height (OR 1.15, 95% CI 1.02 to 1.30), weight (OR 1.40, 95% CI 1.24 to 1.58), BMI (OR 1.26, 95% CI 1.11 to 1.42) and BSA (OR 1.43, 95% CI 1.27 to 1.62) in all adults, but most obviously in women. In children, similar associations were observed between risk of thyroid nodule incidence and weight, BMI and BSA, but not height. BSA was the measurement most significantly associated with thyroid nodules in both adults and children.

CONCLUSIONS

This study identified that the presence of thyroid nodules was positively associated with weight, height, BMI and BSA in both women and girls. It suggests that tall, obese individuals have increased susceptibility to thyroid nodules.

TRIAL REGISTRATION NUMBER

NCT01838629.

Hyperthyroidism and Hypothyroidism in Male Mice and Their Effects on Bone Mass, Bone Turnover, and the Wnt Inhibitors Sclerostin and Dickkopf-1

Thyroid hormones are key regulators of bone homeostasis, and Wnt signaling has been implicated in thyroid hormone-associated bone loss. Here we tested whether hyperthyroidism and hypothyroidism interfere with dickkopf-1 (DKK1) and sclerostin, two inhibitors of Wnt signaling. Twelve-week-old male C57BL/6 mice were rendered either hyperthyroid or hypothyroid. Hyperthyroid mice displayed decreased trabecular (-54%, P < .001) and cortical bone density (-5%, P < .05) and reduced cortical thickness (-15%, P < .001), whereas hypothyroid mice showed a higher trabecular bone density (+26%, P < .001) with unchanged cortical bone parameters. Histomorphometry and biochemical markers of bone remodeling indicated high bone turnover in hyperthyroid mice and low bone turnover in hypothyroid mice. In vivo, serum DKK1 concentrations were decreased in hyperthyroid mice (-24%, P < .001) and increased in hypothyroid mice (+18%, P < .01). The increase of the number of DKK1-positive cells in hypothyroid mice was confirmed at the tissue level. Interestingly, sclerostin was increased in both disease models, although to a higher extent in hyperthyroid mice (+50%, P < .001, and +24%, P < .05). Serum sclerostin concentrations adjusted for bone mass were increased by 3.3-fold in hyperthyroid (P < .001) but not in hypothyroid mice. Consistently, sclerostin mRNA expression and the number of sclerostin-positive cells were increased in hyperthyroid but not in hypothyroid mice. Our data show that thyroid hormone-induced changes in bone remodeling are associated with a divergent regulation of DKK1 and sclerostin. Thus, the modulation of Wnt signaling by thyroid hormones may contribute to thyroid hormone-associated bone disease and altered expression of Wnt inhibitors may emerge as potential therapeutic targets.