Massimo Tonacchera

Bio: Massimo Tonacchera is an academic researcher from University of Pisa. The author has contributed to research in topics: Thyroid & Thyrotropin receptor. The author has an hindex of 42, co-authored 160 publications receiving 5230 citations. Previous affiliations of Massimo Tonacchera include Université libre de Bruxelles & University of Calabria.

Relative potencies and additivity of perchlorate, thiocyanate, nitrate, and iodide on the inhibition of radioactive iodide uptake by the human sodium iodide symporter.

Abstract: The presence of perchlorate (ClO(4) (-)) in some U.S. drinking water supplies has raised concern about potential adverse thyroidal health effects, because ClO(4) (-) is known to competitively inhibit iodide uptake at the sodium iodide symporter (NIS). Humans are nutritionally and environmentally exposed to other competitive inhibitors of iodide uptake, including thiocyanate (SCN(-)) and nitrate (NO(3) (-)). The joint inhibiting effects of these three anions was studied by exposing Chinese hamster ovary cells stably expressing human NIS to varying concentrations of each anion separately, and in combination, and conducting measurements of (125)I(-) uptake. The entire data set was fit to a single Hill equation using maximum likelihood. The relative potency of ClO(4) (-) to inhibit (125)I(-) uptake at the NIS was found to be 15, 30 and 240 times that of SCN(-), I(-), and NO(3) (-) respectively on a molar concentration basis, with no evidence of synergism. These results are consistent with a common mode of action by these anions of simple competitive interaction, in which a concentration of any one of ClO(4) (-) SCN(-), and NO(3) (-), occurring either individually or as part of a mixture of the three anions, is indistinguishable from a concentration or dilution of either one of the remaining two ions in inhibiting iodine uptake at the NIS.

Somatic mutations causing constitutive activity of the thyrotropin receptor are the major cause of hyperfunctioning thyroid adenomas: identification of additional mutations activating both the cyclic adenosine 3',5'-monophosphate and inositol phosphate-Ca2+ cascades.

Abstract: A series of somatic mutations of the TSH receptor gene have been demonstrated in hyperfunctioning thyroid adenomas. The mutations studied up to now cause constitutive (i.e. TSH-independent) activation of the cAMP-regulatory cascade only. As a follow-up to our original study, we have now completely sequenced exon number 10 of the TSH receptor gene in the same series of toxic adenomas. An activating mutation was found in nine of 11 tumors. In addition to the mutations already described, two isoleucine residues belonging to the first and second extracellular loops of the receptor (Ile486 and Ile568) were found mutated. Two different adenomas were found to harbor a different amino acid substitution at residue 486 (Ile486Phe, Ile486Met). Ile568 was mutated to threonine in one. When studied by transfection in COS-7 cells, all three mutations caused very strong activation of the cAMP-regulatory cascade. In addition, the Ile486Phe and, to a lesser extent, the Ile486Met and Ile568Thr mutants stimulated constitutiv...

Somatic and germline mutations of the TSH receptor gene in thyroid diseases.

Abstract: Under physiological circumstances, thyrotropin (TSH) is the primary hormone that controls thyroid function and growth. TSH acts by binding to its receptor at the basolateral membrane of thyroid follicular cells. The TSH receptor is a member of the large family of G protein-coupled receptors, which share a similar structural pattern: seven transmembrane segments connected by three extra and three intracellular loops. Together with the receptors for other glycoprotein hormones LH/CG and FSH, the TSH receptor has a long aminoterminal domain that has been shown to encode the specificity for hormone recognition and binding. The G protein-coupled receptors share a common mode of intracellular signalling: They control the on/off state of a variety of trimeric G proteins (G{alpha}{beta}{gamma}) by stimulating the exchange of GDP for GTP on the {alpha} subunit (G{alpha}). The result is that G{alpha} or G{beta}{gamma}, after dissociation of the trimer, will interact with downstream effectors of the receptor. In the case of the TSH receptor, the main G protein involved is Gs, which activates adenylyl cyclase via Gs{alpha}. In some species, including man, the TSH receptor is also capable of activating phospholipase C (via Gq), thus stimulating the production of diacylglycerol and inositolphosphate (IP{sub 3}). However, higher concentrationsmore » of TSH are required to activate phospholipase C, compared with adenylyl cyclase. As a consequence, the main second messenger of TSH effects on the human thyroid is cyclic AMP. The present review will summarize recent findings identifying mutations of the TSH receptor gene as a cause for thyroid diseases. 59 refs., 4 figs.« less

Expression of IP-10/CXCL10 and MIG/CXCL9 in the thyroid and increased levels of IP-10/CXCL10 in the serum of patients with recent-onset Graves' disease.

Abstract: Both mRNA and protein expression of the chemokines IP-10/CXCL10 and Mig/CXCL9, as well as of their receptor, CXCR3, were assessed in the thyroid glands of 16 patients suffering from Graves' disease (GD). In addition, IP-10/CXCL10 levels were measured in the serum of 50 GD patients. Expression of IP-10/CXCL10, Mig/CXCL9, and CXCR3 was poor or absent in normal thyroid tissue from patients undergoing thyroidectomy because of primary localized thyroid tumors, while both the chemokines and their receptor were present in most thyroid glands of patients affected by GD. IP-10/CXCL10 and Mig/CXCL9 localized to infiltrating lymphocytes and macrophages, as well as to resident epithelial follicular cells, whereas CXCR3 was mainly found at the level of infiltrating inflammatory cells and endothelial cells from large and small vessels. Of note, maximal expression of IP-10/CXCL10 and Mig/CXCL9 was found in the thyroid gland of patients with recent-onset GD and was correlated with interferon (IFN)-γ. Accordingly, high levels of IP-10/CXCL10 could be measured in the serum of patients with short-duration GD. Taken together, the results of this study demonstrate that the CXCR3-binding chemokines IP-10/CXCL10 and Mig/CXCL9 play an important role in the recruitment of cells and in the amplification of inflammation in GD. They also suggest that the production of these chemokines by resident follicular epithelial cells may contribute to the recruitment of CXCR3-expressing type 1 T-helper cells in the initial phases of GD.

Functional characteristics of three new germline mutations of the thyrotropin receptor gene causing autosomal dominant toxic thyroid hyperplasia.

Abstract: We report three unrelated families in which hyperthyroidism associated with thyroid hyperplasia was transmitted in an autosomal dominant fashion, in the absence of signs of autoimmunity. Exon 10 of the TSH receptor gene was directly sequenced after PCR amplification from DNA of peripheral leukocytes. In one family, a C to A transversion resulted in an S505R substitution in the third transmembrane segment; in the second, an A to T transversion caused a N650Y substitution in the sixth transmembrane segment; and in the third family, an A to G transition resulted in an N670S substitution in the seventh transmembrane segment. When expressed by transfection in COS-7 cells, each mutated receptor displayed an increase in constitutive stimulation of cAMP production; no effect on basal accumulation of inositol phosphates (IP) could be detected. In binding studies, cells transfected with wild-type or mutated receptors showed similar levels of expression, with the mutated receptors displaying similar or slightly increased affinity for bovine TSH (bTSH) binding. Cells transfected with S505R and N650Y mutants showed a similar cAMP maximal TSH-stimulated accumulation over the cells transfected with the wild type, whereas N670S transfectants showed a blunted response with an increase in EC50. A higher IP response to 100 mU/mL bTSH over that obtained with the wild-type receptor was obtained in cells transfected with N650Y; in contrast, cells transfected with S505R showed a blunted IP production (50% less), and the N670S mutant completely lost the ability to stimulate IP accumulation in response to bTSH. The differential effects of individual mutations on stimulation by bTSH of cAMP or IP accumulation suggest that individual mutant receptors may achieve different active conformations with selective abilities to couple to Gs alpha and to Gq alpha.

2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer: The American Thyroid Association Guidelines Task Force on Thyroid Nodules and Differentiated Thyroid Cancer.

Abstract: Background: Thyroid nodules are a common clinical problem, and differentiated thyroid cancer is becoming increasingly prevalent. Since the American Thyroid Association's (ATA's) guidelines for the management of these disorders were revised in 2009, significant scientific advances have occurred in the field. The aim of these guidelines is to inform clinicians, patients, researchers, and health policy makers on published evidence relating to the diagnosis and management of thyroid nodules and differentiated thyroid cancer. Methods: The specific clinical questions addressed in these guidelines were based on prior versions of the guidelines, stakeholder input, and input of task force members. Task force panel members were educated on knowledge synthesis methods, including electronic database searching, review and selection of relevant citations, and critical appraisal of selected studies. Published English language articles on adults were eligible for inclusion. The American College of Physicians Guideline Gr...

2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum

Abstract: Background: Thyroid disease in pregnancy is a common clinical problem. Since the guidelines for the management of these disorders by the American Thyroid Association (ATA) were first published in 2...

Clinical spectrum of obesity and mutations in the melanocortin 4 receptor gene.

Abstract: Background Melanocortin 4 receptor (MC4R) deficiency is the commonest monogenic form of obesity. However, the clinical spectrum and mode of inheritance have not been defined, pathophysiological mechanisms leading to obesity are poorly understood, and there is little information regarding genotype–phenotype correlations. Methods We determined the nucleotide sequence of the MC4R gene in 500 probands with severe childhood obesity. Family studies were undertaken to examine cosegregation of identified mutations with obesity. Subjects with MC4R deficiency underwent metabolic and endocrine evaluation; the results were correlated with the signaling properties of mutant receptors. Results Twenty-nine probands (5.8 percent) had mutations in MC4R; 23 were heterozygous, and 6 were homozygous. Mutation carriers had severe obesity, increased lean mass, increased linear growth, hyperphagia, and severe hyperinsulinemia; homozygotes were more severely affected than heterozygotes. Subjects with mutations retaining residual...

Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and Postpartum The American Thyroid Association Taskforce on Thyroid Disease During Pregnancy and Postpartum

Abstract: Pregnancy has a profound impact on the thyroid gland and thyroid function. The gland increases 10% in size during pregnancy in iodine-replete countries and by 20%– 40% in areas of iodine deficiency. Production of thyroxine (T4) and triiodothyronine (T3) increases by 50%, along with a 50% increase in the daily iodine requirement. These physiological changes may result in hypothyroidism in the later stages of pregnancy in iodine-deficient women who were euthyroid in the first trimester. The range of thyrotropin (TSH), under the impact of placental human chorionic gonadotropin (hCG), is decreased throughout pregnancy with the lower normal TSH level in the first trimester being poorly defined and an upper limit of 2.5 mIU/L. Ten percent to 20% of all pregnant women in the first trimester of pregnancy are thyroid peroxidase (TPO) or thyroglobulin (Tg) antibody positive and euthyroid. Sixteen percent of the women who are euthyroid and positive for TPO or Tg antibody in the first trimester will develop a TSH that exceeds 4.0 mIU/L by the third trimester, and 33%–50% of women who are positive for TPO or Tg antibody in the first trimester will develop postpartum thyroiditis. In essence, pregnancy is a stress test for the thyroid, resulting in hypothyroidism in women with limited thyroidal reserve or iodine deficiency, and postpartum thyroiditis in women with underlying Hashimoto’s disease who were euthyroid prior to conception. Knowledge regarding the interaction between the thyroid and pregnancy/the postpartum period is advancing at a rapid pace. Only recently has a TSH of 2.5 mIU/L been accepted as the upper limit of normal for TSH in the first trimester. This has important implications in regards to interpretation of the literature as well as a critical impact for the clinical diagnosis of hypothyroidism. Although it is well accepted that overt hypothyroidism and overt hyperthyroidism have a deleterious impact on pregnancy, studies are now focusing on the potential impact of subclinical hypothyroidism and subclinical hyperthyroidism on maternal and