The Presence of Thyroid-Stimulation Blocking Antibody Prevents High Bone Turnover in Untreated Premenopausal Patients with Graves' Disease

TSH-secreting pituitary adenomas and bone

TSH-secreting pituitary adenoma (TSHoma) is the rarest functioning pituitary tumor, with an increasing incidence over the last decades. Diagnosis is often delayed, exposing patients to a high risk of developing chronic complications of long-standing hyperthyroidism. Although thyroid hormone excess is a recognized cause of secondary osteoporosis, very few studies have investigated skeletal damage in patients with TSHoma, with data limited to bone turnover markers (BTM) and a study on the prevalence of radiological vertebral fractures (VFs) incidentally detected on chest X-ray, whereas data on bone mineral density (BMD) are anecdotal. Bone resorption is increased in TSHoma compared to controls, whereas few case reports described osteoporosis and spine fractures as early complications of TSHoma. A high prevalence of morphometric VFs was described in TSHoma compared to nonfunctioning pituitary adenoma (NFPA). Patients with fracture were older and had higher free thyroxine (fT4) levels than patients without fracture. In this specific setting, treatment with somatostatin receptor ligands seems to have a protective role on fracture risk. Based on this evidence, a comprehensive osteometabolic evaluation should be performed in all patients with TSHoma, including assessment of BTM, measurement of BMD, and morphometric evaluation of VFs, both at diagnosis and then during follow-up, particularly in patients at high risk for fragility fractures.

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.

Pituitary crosstalk with bone, adipose tissue and brain

Traditional textbook physiology has ascribed unitary functions to hormones from the anterior and posterior pituitary gland, mainly in the regulation of effector hormone secretion from endocrine organs. However, the evolutionary biology of pituitary hormones and their receptors provides evidence for a broad range of functions in vertebrate physiology. Over the past decade, we and others have discovered that thyroid-stimulating hormone, follicle-stimulating hormone, adrenocorticotropic hormone, prolactin, oxytocin and arginine vasopressin act directly on somatic organs, including bone, adipose tissue and liver. New evidence also indicates that pituitary hormone receptors are expressed in brain regions, nuclei and subnuclei. These studies have prompted us to attribute the pathophysiology of certain human diseases, including osteoporosis, obesity and neurodegeneration, at least in part, to changes in pituitary hormone levels. This new information has identified actionable therapeutic targets for drug discovery.

IMPACT OF GRAVES' DISEASE AND ANTITHYROID DRUG THERAPY ON BONE MINERAL DENSITY - PATHOPHYSIOLOGICAL MECHANISMS AND CLINICAL RELEVANCE

Graves' disease is an autoimmune disease characterized by excessive thyroid hormone production. One of the consequences of that state can be a decrease in bone mineral density (BMD). Graves' disease is often treated with antithyroid drugs (ATD) as first line therapy, which can lead to disease remission. Moreover, recent data show that improvement in BMD can be expected. However, vitamin D deficiency can coexist along with Graves' disease, which is also involved in the process of bone remodeling. It is still not known whether lower values of vitamin D can contribute to onset of Graves' disease and if its supplementation might be helpful in therapy for hyperthyroidism. In the past couple of decades, osteopenia and osteoporosis have become a major health burden not only in post-menopausal women but also as a result of other diseases, leading to extensive research into various pathophysiological mechanisms responsible for bone remodeling. The Wnt (wingless integrated) signaling pathway is a very important factor in bone homeostasis, especially the canonical pathway. Present data indicate that stimulation of the Wnt pathway leads to bone mass increase and, in contrast, its inhibition leads to bone mass decrease. Hence, inhibitors of the canonical Wnt pathway became the focus of interest, in particular sclerostin and dickkopf 1 (DKK1). Hyperthyroidism and osteopenia/osteoporosis are quite common today and can coexist together or as separate entities. In this article, we aimed to give an overview of possible associations and potential mutual pathophysiological mechanisms.

Serum interferon levels associated with the disease activity in women with overt Graves' disease

BACKGROUND

Inflammatory cytokines participate in immune reactions and the pathogenesis of autoimmunity. Herein, we quantified four groups of inflammatory cytokines, including interferons (IFNs), the tumor necrosis factor (TNF) superfamily (TNFSF), interleukin (IL)-related cytokines, and bone and extracellular matrix remodeling-related cytokines to determine their contributions in women with overt Graves' disease (GD).

METHODS

Forty-three women with GD were enrolled in this cross-sectional study. Thirty-seven cytokines, thyroid-stimulating hormone (TSH), free thyroxine, and TSH receptor antibody (TSHRAb) were quantified. GD patients with a low TSH level at the time of sample collection were defined as having active GD.

RESULTS

Patients with active GD had higher IFN-α2, IFN-γ, IFN-λ1, and IFN-λ2 levels than those with inactive GD. In addition, certain TNFSF cytokines, including soluble cluster of differentiation 30 (sCD30), TNFSF member 14 (TNFSF14), pentraxin (PTX)-3, soluble TNF receptor 2 (sTNF-R2), and thymic stromal lymphopoietin (TSLP) were higher in active GD than in inactive GD. Moreover, active GD patients had higher IL-2, IL-12(p40), osteocalcin (OCN), and matrix metalloproteinase (MMP)-3 than inactive GD patients. All IFNs except IFN-λ1 were correlated with TSHRAb titers. Moreover, TNFSF cytokines, consisting of B-cell-activating factor, sCD30, TNFSF14, PTX-3, sTNF-R2, and TSLP, were associated with TSHRAb levels.

CONCLUSIONS

Serum IFNs could be the most remarkable cytokines in modulating the disease severity and TSHRAb titers in women with full-blown GD. Further molecular-based research to clarify the actual role of IFNs in the disease progression of GD is needed.

Graves' disease and vertebral fracture: Possible pathogenic link in postmenopausal women

BACKGROUND AND OBJECTIVE

Thyrotoxicosis is associated with accelerated bone turnover and increases the risk of fractures and osteoporosis. Graves' disease is the most common cause of hyperthyroidism. However, studies that examined risk factors associated with fragility fractures only in patients with Graves' disease are limited. Here, we investigated whether the risk of vertebral fracture (VF) of postmenopausal Graves' disease patients is high and tried to identify the risk factors for VF in that population.

DESIGN AND METHODS

Forty-three postmenopausal women with Graves' disease were enrolled. Physical and biochemical indices, thyroid indices and bone mineral density (BMD) were measured, and lateral X-rays were obtained to evaluate VFs. Age- and sex-matched healthy individuals were enrolled as the control group (n = 86).

RESULTS

The prevalence of VFs (35% vs 17%, P < .05), osteoporosis (63% vs 33%, P < .01) and severe osteoporosis (40% vs 17%, P < .01) was significantly higher in the Graves' disease group. Although there was no significant difference in either thyroid hormone levels or the positive ratio of thyroid antibodies, the prevalence of thyroid-stimulating antibody (TSAb) was significantly higher in Graves' disease patients with VF compared to without (100% vs 68%, P < .05). Multivariate logistic regression analyses adjusted for age identified Graves' disease as being associated with the presence of VFs (OR 2.72, 95% CI: 1.13-6.54, P < .05) in postmenopausal women.

CONCLUSIONS

Postmenopausal Graves' disease patients had high risks of VF and severe osteoporosis. TSAb could be involved as a risk factor for VF in postmenopausal Graves' disease.

Serum fibroblast growth factor 23 and mineral metabolism in patients with euthyroid Graves' diseases: a case-control study

This study investigated the alterations of mineral metabolism in patients with Graves' disease (GD) who achieved euthyroidism. They had higher fibroblast growth factor 23 (FGF23) and phosphorus as compared with healthy subjects. Serum FGF23 was negatively correlated with serum phosphorus. These indicated abnormal mineral metabolism even after 1.6 years of euthyroid status.

INTRODUCTION

FGF23 is involved in the mineral homeostasis, especially the regulation of serum phosphorus. Graves' disease (GD) is associated with accelerated bone turnover, hyperphosphatemia, and elevated serum FGF23. Evidence suggested that serum FGF23 decreased after a 3-month treatment of GD. However, it remains unclear whether serum FGF23, serum phosphorus, and other markers of mineral metabolism will be normalized after euthyroid status achieved.

METHODS

A total of 62 patients with euthyroid GD and 62 healthy control subjects were enrolled, and the median duration of euthyroid status was 1.6 years. Endocrine profiles including thyroid function test, autoantibodies, serum FGF23, and bone turnover markers were obtained and compared between the two groups.

RESULTS

Euthyroid GD patients had significantly higher serum FGF23 and phosphorus, and lower 25-hydroxyvitamin D (25(OH)D) and intact parathyroid hormone (iPTH) levels as compared with the control group. Serum FGF23 was significantly and negatively correlated with phosphorus level after adjusted for age, gender, calcium, iPTH, and 25(OH)D in the euthyroid GD group.

CONCLUSION

Serum phosphorus and FGF23 levels remain higher in GD patients even after euthyroid status has been achieved for a median of 1.6 years. Serum FGF23 was negatively correlated with serum phosphorus in euthyroid GD patients. Underlying mechanisms warrant further investigations.

TRIAL REGISTRATION

Registration number: NCT01660308 and NCT02620085.

Actions of pituitary hormones beyond traditional targets

Studies over the past decade have challenged the long-held belief that pituitary hormones have singular functions in regulating specific target tissues, including master hormone secretion. Our discovery of the action of thyroid-stimulating hormone (TSH) on bone provided the first glimpse into the non-traditional functions of pituitary hormones. Here we discuss evolving experimental and clinical evidence that growth hormone (GH), follicle-stimulating hormone (FSH), adrenocorticotrophic hormone (ACTH), prolactin, oxytocin and arginine vasopressin (AVP) regulate bone and other target tissues, such as fat. Notably, genetic and pharmacologic FSH suppression increases bone mass and reduces body fat, laying the framework for targeting the FSH axis for treating obesity and osteoporosis simultaneously with a single agent. Certain 'pituitary' hormones, such as TSH and oxytocin, are also expressed in bone cells, providing local paracrine and autocrine networks for the regulation of bone mass. Overall, the continuing identification of new roles for pituitary hormones in biology provides an entirely new layer of physiologic circuitry, while unmasking new therapeutic targets.

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.

Liver-specific deletion of TSHR inhibits hepatic lipid accumulation in mice

The effect of thyroid-stimulating hormone receptor (TSHR) on hepatic lipid accumulation in vivo is not fully understood. Further, while TSHR in the thyroid has been studied extensively, whether and how the absence of TSHR in the liver affects systemic energy metabolism has not yet been reported. To examine these effects, we generated hepatic TSHR conditional knockout (LT-KO) mice using Cre/LoxP recombination technology. The liver-specific TSHR-knockout (LT-KO) mice exhibited not only lower hepatic triglyceride and cholesterol contents due to modified synthesis and catabolism of lipids in the liver, but also decreased serum lipids, especially serum LDL-C levels. Abnormalities of TSHR in the thyroid affect whole-body energy balance; however, measurements taken in metabolic chambers showed that the hepatic TSHR conditional deletion had no impact on systemic energy metabolism. Unlike its critical role in maintaining the normal growth and function of the thyroid gland, our results demonstrated that hepatic TSHR is involved in liver lipid metabolism and has little effect on energy metabolism.

The characteristics of osteoporotic patients in Graves' disease patients newly diagnosed after menopause: a prospective observational study

Overt hyperthyroidism is associated with reduced bone density. The extent of restoration of reduced bone density caused by hyperthyroidism in postmenopausal Graves' disease (GD) patients has not fully been investigated. We examined 85 newly diagnosed postmenopausal GD patients, and we measured their serum thyroid hormone levels as well as their bone turnover marker levels and the bone mineral density (BMD) of their lumbar spine (LS), both femoral necks (FN), and left distal radius (DR). We prospectively observed the patients for changes in BMD and bone turnover marker levels during a 24-month period after euthyroidism had been established by ATD treatment. The median age of the subjects was 57 years old (range: 50 to 79). 46 (54.1%) patients had osteoporosis. 42 of the 46 osteoporosis patients had low BMD in the DR. The patients with osteoporosis were significantly older, had a significantly lower BMI, and had significantly higher bone turnover marker levels compared to the normal BMD patients. The best predictor of the BMD in the DR was BMD in the FN (β = 0.40, p < 0.0001). A total of 42 patients were followed up for 24 months after attainment of euthyroidism, and 19 of them were osteoporosis at the first visit. The BMD of the 19 osteoporotic patients had increased by 4.9% in the LS, 11.9% in the FN, and 9.3% in the DR at 24 months. After maintaining a euthyroid state for 24 months by means of ATD treatment, 26% of the osteoporotic patients had recovered from osteoporosis.