Modulation of Fas-mediated apoptosis of human thyroid epithelial cells by IgG from patients with Graves' disease (GD) and idiopathic myxoedema

The expression of two autoimmune thyroid diseases, GD and idiopathic myxoedema, is associated with antibodies to the thyroid-stimulating hormone (TSH) receptor. Thyroid stimulating antibodies (TSAb) in GD are TSH agonists and cause hyperthyroidism as well as goitre, whereas thyroid stimulation blocking antibodies (TSBAb) in idiopathic myxoedema are TSH antagonists and cause hypothyroidism and thyroid atrophy. We investigated the effect of antibodies to TSH receptor on Fas-mediated apoptosis of thyroid epithelial cells (thyrocytes). Human IgG was isolated from healthy donors, patients with GD and idiopathic myxoedema. Human thyrocytes were obtained from surgical specimens. Thyrocytes were cultured in the presence or absence of human IgG with or without interferon-gamma (IFN-γ) or IL-1β for a specified time. After incubation, we examined the level of cAMP in cultured supernatants and both Fas and Bcl-2 expression on thyrocytes. In addition, we examined anti-Fas-mediated apoptosis of thyrocytes. Fas expression on thyrocytes was significantly down-regulated by Graves' IgG and TSH, although idiopathic myxoedema IgG did not affect Fas expression on thyrocytes. Idiopathic myxoedema IgG abrogated the effect of TSH on both cAMP production and inhibition of Fas expression on thyrocytes. Treatment of thyrocytes with IL-1β or IFN-γ caused a marked augmentation of Fas expression on thyrocytes. The increase of Fas expression of thyrocytes induced by IL-1β or IFN-γ was significantly suppressed in the presence of TSH or Graves' IgG. Anti-Fas-induced apoptosis of thyrocytes was observed in thyrocytes treated with IL-1β or IFN-γ, but was markedly inhibited in the presence of TSH or Graves' IgG. Furthermore, idiopathic myxoedema IgG abrogated most of the inhibitory effect of TSH on Fas-mediated apoptosis of thyrocytes treated with IL-1β or IFN-γ. Bcl-2 expression of thyrocytes did not change after stimulation with TSH, Graves' IgG, idiopathic myxoedema IgG, IL-1β or IFN-γ. These results suggest that TSAb found in Graves' patients may be potentially involved in the development of goitre by inhibition of Fas-mediated apoptosis of thyrocytes. In addition, TSBAb inhibit the action of TSH and increase the sensitivity toward Fas-mediated apoptosis of thyrocytes, inducing thyroid atrophy seen in patients with idiopathic myxoedema.     

Prolonged suppressed thyroid-stimulating hormone levels in hyperthyroidism in a neonate born to a mother with Graves' disease

Abstract We report here a case of neonatal hyperthyroidism born to a mother, whose pregnancy was complicated by poorly controlled Graves' disease. The patient demonstrated exophthalmos and marked goiter at birth, indicating the existence of thyrotoxicosis in utero. The mother's Graves' disease was well controlled in the third trimester, resulting in a slightly lower level of free thyroxine (FT₄) in the umbilical cord blood serum; however, thyroid-stimulating hormone (TSH) was undetectable. Thyroid-stimulating hormone remained undetectable for 2 months, while FT₄ levels varied in the course. This case suggests that severe and prolonged thyrotoxicosis in utero, due to poor control of pregnancy with Graves' disease, might induce unresponsiveness of the hypothalamo-pituitary system in the newborn.     

Direct visualization of membrane clustering and endocytosis of thyrotropin into cultured thyroid cells

We prepared a highly fluorescent conjugate of thyrotropin (TSH) which retains approximately 25% of the binding affinity of native TSH towards TSH receptor and approximately 25% of the potency of the native hormone in stimulating the accumulation of cAMP in thyroid cells. Using an image-intensified microscopy system, we observed that our fluorescent TSH bound specifically to diffusely distributed membrane receptors on live rat or bovine embryo thyroid cells grown in culture. At 37 degrees C the fluorescent hormone formed visible patches which were internalized and subsequently degraded. Hence, TSH, like other polypeptide hormones, is internalized by a process of receptor-mediated endocytosis. The addition of bivalent antibodies against the fluorophore rhodamine, to thyroid cells that were previously exposed to sub-optimal concentrations of rhodamine TSH, elicited maximal stimulation of the thyroid adenyl cyclase. Monovalent Fab' fragments did not enhance the response of rhodamine TSH. Therefore we conclude that enhanced surface clustering of TSH molecules increases their capacity to stimulate the adenyl cyclase of thyroid cells.     

Graves病患者促甲状腺激素受体抗体与肝功能指标的关系

目的 探讨Graves病患者促甲状腺激素受体抗体（TRAb）与肝功能各指标间的关系。方法 选取 2014年1月—2018年6月南京中医药大学附属医院内分泌科收治的Graves病患者231例。其中,男性53例, 女性178例。检测所有患者TRAb、甲状腺功能及肝功能指标;通过非参数检验、Logistic回归模型分析及ROC曲线,分析Graves病患者肝功能异常指标与TRAb的关联性。结果 231例患者中,有58.4%患者存在不同程度的肝功能受损;TRAb水平四分位分组后发现,随着TRAb水升高,游离三碘甲腺原氨酸（FT3）和游离甲状腺素（FT4）上升（P?<0.05）,而肝功能指标中只有碱性磷酸酶（ALP）的组间比较,差异有统计学意义 （P?<0.05）;在控制性别、年龄、FT3、FT4和其他肝功能指标后,Logistic回归模型分析结果显示,随着TRAb水平升高,血清ALP升高的相对危险度增加（P?<0.05）,TRAb水平四分位的OlR值达3.284（95% CI：1.221, 8.832）;ROC曲线分析显示,当TRAb≥11.96?IU/L时,ALP升高的危险增加。结论 TRAb水平是Graves病 患者ALP升高的影响因素。     

Thyroid effects of endocrine disrupting chemicals

In recent years, many studies of thyroid-disrupting effects of environmental chemicals have been published. Of special concern is the exposure of pregnant women and infants, as thyroid disruption of the developing organism may have deleterious effects on neurological outcome. Chemicals may exert thyroid effects through a variety of mechanisms of action, and some animal experiments and in vitro studies have focused on elucidating the mode of action of specific chemical compounds. Long-term human studies on effects of environmental chemicals on thyroid related outcomes such as growth and development are still lacking. The human exposure scenario with life long exposure to a vast mixture of chemicals in low doses and the large physiological variation in thyroid hormone levels between individuals render human studies very difficult. However, there is now reasonably firm evidence that PCBs have thyroid-disrupting effects, and there is emerging evidence that also phthalates, bisphenol A, brominated flame retardants and perfluorinated chemicals may have thyroid disrupting properties.     

Mildly elevated thyroid-stimulating hormone is associated with endothelial dysfunction and severe preeclampsia among pregnant women with insufficient iodine intake in Eastern Cape province,South Africa

BackgroundPreeclampsia and hypothyroidism are associated with endothelial dysfunction. Iodine deficiency is a risk factor for subclinical hypothyroidism in pregnancy. However, there is a paucity of data on the relationship between iodine nutrition state in pregnancy, the degree of endothelial dysfunction, and the risk of preeclampsia.MethodsNinety-five normotensive pregnant women, 50 women with preeclampsia with no severe features, and 50 women with severe preeclampsia were enrolled into the current study from the maternity units of Nelson Mandela Academic Hospital and Mthatha Regional Hospitals in Eastern Cape Province, South Africa. Urinary iodine concentration (UIC), serum markers of thyroid function, aortic augmentation index, and pulse wave velocity (PWV) were compared.ResultsMedian UIC was 167.5, 127.7, and 88.5 µg/L, respectively for normotensive pregnant women, those with preeclampsia and severe preeclampsia (p = .150). Participants with severe preeclampsia had significantly higher median thyroid-stimulating hormone (TSH) and oxidized LDL than normotensive and preeclamptic women without severe features (respectively 3.0, 2.3, and 2.3 IU/L; 1.2, 1.0, and 1.0 IU/L, p < .05). The median Aortic augmentation index was 7.5, 19.0, and 21.0 (p < .001), and the pulse wave velocity 5.1, 5.7, and 6.3, respectively for normotensive, preeclampsia, and severe preeclampsia participants (both p < .001). In linear regressions, TSH, age, and hypertensive disease were independent predictors of elevated PWV.ConclusionUpper normal-range TSH levels in women with severe preeclampsia were associated with markers of endothelial dysfunction. The low UIC and trend towards the elevation of thyroglobulin suggest that inadequate iodine intake may have increased TSH levels and indirectly caused endothelial dysfunction.     

Somatostatin receptors: From signaling to clinical practice

Somatostatin is a peptide with a potent and broad antisecretory action, which makes it an invaluable drug target for the pharmacological management of pituitary adenomas and neuroendocrine tumors. Somatostatin receptors (SSTR1, 2A and B, 3, 4 and 5) belong to the G protein coupled receptor family and have a wide expression pattern in both normal tissues and solid tumors. Investigating the function of each SSTR in several tumor types has provided a wealth of information about the common but also distinct signaling cascades that suppress tumor cell proliferation, survival and angiogenesis. This provided the rationale for developing multireceptor-targeted somatostatin analogs and combination therapies with signaling-targeted agents such as inhibitors of the mammalian (or mechanistic) target of rapamycin (mTOR). The ability of SSTR to internalize and the development of rabiolabeled somatostatin analogs have improved the diagnosis and treatment of neuroendocrine tumors.     

Recovery of insulin sensitivity and Slc2a4 mRNA expression depend on T3 hormone during refeeding

Objective

GLUT4 protein, encoded by the Slc2a4 gene, plays a key role in muscle glucose uptake, and its expression decreases in muscles under insulin resistance. Slc2a4/GLUT4 decreases with fasting and rapidly increases with refeeding and the same occurs to plasma glucose, amino acids, insulin and T3. Thus, they might be potential regulators of the Slc2a4 gene, which makes them promising targets for strategies to improve GLUT4 expression. Herein, we investigate the role of metabolic–hormonal parameters triggered by refeeding upon the Slc2a4 expression.

Materials/Methods

Plasma glucose/insulin/T3, and gastrocnemius Slc2a4 mRNA contents were measured in rats studied at the end of 48-h fasting, and subsequently at: i) 2–4 h after spontaneous refeeding; ii) 2–4 h after T3 injection, without refeeding; and iii) 0.5–2 h after intravenous infusion of insulin, insulin + glucose and insulin + amino acids, without refeeding.

Results

Refeeding increased plasma glucose/insulin/T3 and muscle Slc2a4 mRNA, reverting insulin resistance. Post-fasting infusions surprisingly induced a further Slc2a4 mRNA decrease (~ 20%, P < 0.05 vs. fasting), but T3 injection induced a ~ 2-fold increase in Slc2a4 mRNA, 2–4 h later (P < 0.001). Moreover, T3 increased glycemia and insulinemia to the 2 h-refed rats levels, suggesting that T3 elevation is a key factor to the mechanisms of metabolic balance during refeeding.

Conclusions

Refeeding induces a rapid increase in muscle Slc2a4 expression, not associated with increased plasma glucose, insulin or amino acids, but highly correlated to increased plasma T3 concentration. This result points out T3 hormone as a powerful Slc2a4 enhancer, an effect that may be acutely explored in situations of insulin resistance.     

碘与亚临床甲状腺功能减退症的关系

碘是人体必需微量元素,过多过少都会影响人体健康。碘缺乏疾病引起的关注较多,而碘过量有损健康的宣传却较少。长期过量碘摄入影响甲状腺功能,所致甲状腺疾病发病率明显上升,其中甲状腺功能减退症和亚临床甲状腺功能减退症的患病率呈增加趋势。过量碘摄入致亚临床甲状腺功能减退症和甲状腺功能减退症是一个从量变到质变的过程,应当加强公共卫生、临床工作中对碘摄入量的控制和管理,制订因地制宜、因人而异的碘摄入量标准。