SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Hyperthyroidism

172

The endocrine system and particular endocrine organs, including the thyroid, undergo important functional changes during aging. The prevalence of thyroid disorders increases with age and numerous morphological and physiological changes of the thyroid gland during the process of aging are well-known. It is to be stressed that the clinical course of thyroid diseases in the elderly differs essentially from that observed in younger individuals, because symptoms are more subtle and are often attributed to normal aging. Subclinical hypo- and hyperthyroidism, as well as thyroid neoplasms, require special attention in elderly subjects. Intriguingly, decreased thyroid function, as well as thyrotropin (TSH) levels – progressively shifting to higher values with age – may contribute to the increased lifespan.This short review focuses on recent findings concerning the alterations in thyroid function during aging, including these which may potentially lead to extended longevity, both in humans and animals.

Concepts: Thyroid disease, Hypothyroidism, Hashimoto's thyroiditis, Hyperthyroidism, Thyroid, Graves' disease, Endocrine system, Triiodothyronine

171

Autoimmune thyroid disease (AITD), including Graves' disease (GD) and Hashimoto’s thyroiditis (HT), is one of the most common of the immune-mediated diseases. To further investigate the genetic determinants of AITD, we conducted an association study using a custom-made single-nucleotide polymorphism (SNP) array, the ImmunoChip. The SNP array contains all known and genotype-able SNPs across 186 distinct susceptibility loci associated with one or more immune-mediated diseases. After stringent quality control, we analysed 103 875 common SNPs (minor allele frequency >0.05) in 2285 GD and 462 HT patients and 9364 controls. We found evidence for seven new AITD risk loci (P < 1.12 × 10(-6); a permutation test derived significance threshold), five at locations previously associated and two at locations awaiting confirmation, with other immune-mediated diseases.

Concepts: Bioinformatics, Single-nucleotide polymorphism, Thyroid disease, Genetic genealogy, Hashimoto's thyroiditis, Hyperthyroidism, Thyroid, Minor allele frequency

170

C.RF-Tshr(hyt/hyt) mice have a mutated thyroid stimulating hormone receptor (P556L-TSHR) and these mice develop severe hypothyroidism. We found that C.RF-Tshr(hyt/wild) heterozygous mice are also in a hypothyroid state. Thyroid glands from C.RF-Tshr(hyt/wild) mice are smaller than those from wild-type mice, and (125)I uptake activities of the former are significantly lower than those in the latter. When TSHR (TSHR(W)) and P556L-TSHR (TSHR(M)) cDNAs were cloned and co-transfected into HEK 293 cells, the cells retained (125)I-TSH binding activity, but cAMP response to TSH was decreased to about 20% of HEK 293 cells transfected with TSHR(W) cDNA. When TSHR(W) and TSHR(M) were tagged with eCFP or eYFP, we observed fluorescence resonance energy transfer (FRET) in HEK 293 cells expressing TSHR(W)-eCFP and TSHR(W)-eYFP in the absence of TSH, but not in the presence of TSH. In contrast, we obtained FRET in HEK 293 cells expressing TSHR(W)-eCFP and TSHR (M)-eYFP, regardless of the presence or absence of TSH. These results suggest that P556L TSHR has a dominant negative effect on TSHR(W) by impairing polymer to monomer dissociation, which decreases TSH responsiveness and induces hypothyroidism in C.RF-Tshr(hyt/wild) mice.

Concepts: DNA, Thyroid-stimulating hormone, Hypothyroidism, Hashimoto's thyroiditis, Hyperthyroidism, Thyroid hormone, Förster resonance energy transfer, HEK cell

169

Thyroid hormone is essential for normal metabolism and development, and overt abnormalities in thyroid function lead to common endocrine disorders affecting approximately 10% of individuals over their life span. In addition, even mild alterations in thyroid function are associated with weight changes, atrial fibrillation, osteoporosis, and psychiatric disorders. To identify novel variants underlying thyroid function, we performed a large meta-analysis of genome-wide association studies for serum levels of the highly heritable thyroid function markers TSH and FT4, in up to 26,420 and 17,520 euthyroid subjects, respectively. Here we report 26 independent associations, including several novel loci for TSH (PDE10A, VEGFA, IGFBP5, NFIA, SOX9, PRDM11, FGF7, INSR, ABO, MIR1179, NRG1, MBIP, ITPK1, SASH1, GLIS3) and FT4 (LHX3, FOXE1, AADAT, NETO1/FBXO15, LPCAT2/CAPNS2). Notably, only limited overlap was detected between TSH and FT4 associated signals, in spite of the feedback regulation of their circulating levels by the hypothalamic-pituitary-thyroid axis. Five of the reported loci (PDE8B, PDE10A, MAF/LOC440389, NETO1/FBXO15, and LPCAT2/CAPNS2) show strong gender-specific differences, which offer clues for the known sexual dimorphism in thyroid function and related pathologies. Importantly, the TSH-associated loci contribute not only to variation within the normal range, but also to TSH values outside the reference range, suggesting that they may be involved in thyroid dysfunction. Overall, our findings explain, respectively, 5.64% and 2.30% of total TSH and FT4 trait variance, and they improve the current knowledge of the regulation of hypothalamic-pituitary-thyroid axis function and the consequences of genetic variation for hypo- or hyperthyroidism.

Concepts: Genetics, Atrial fibrillation, Hypothyroidism, Hyperthyroidism, Thyroid, Thyroid hormone, Endocrine system, Triiodothyronine

168

BACKGROUND: We would like to investigate the if IMRT produced better target coverage and dose sparing to adjacent normal structures as compared with 3DCRT and LOF for patients with Graves' ophthalmopathy treated with retro-orbital irradiation. METHODS: Ten consecutive patients diagnosed with Graves' ophthalmopathy were prospectively recruited into this study. An individual IMRT, 3DCRT and LOF plan was created for each patient. Conformity index (CI), homogeneity index (HI) and other dosimetric parameters of the targets and organs-at-risk (OAR) generated by IMRT were compared with the other two techniques. RESULTS: Mann–Whitney U test demonstrated that CI generated by IMRT was superior to that produced by 3DCRT and LOF (p=0.005 for both respectively). Similarly HI with IMRT was proven better than 3DCRT (p=0.007) and LOF (p=0.005). IMRT gave rise to better dose sparing to some OARs including globes, lenses and optic nerves as compared with 3DCRT but not with LOF. CONCLUSIONS: IMRT, as compared with 3DCRT and LOF, was found to have a better target coverage, conformity and homogeneity and dose sparing to some surrounding structures, despite a slight increase but clinically negligible dose to other structures. Dosimetrically it might be a preferred treatment technique and a longer follow up is warranted to establish its role in routine clinical use.

Concepts: Hospital, Thyroid disease, Hyperthyroidism, Target Corporation, Graves' ophthalmopathy

157

Background The use of levothyroxine to treat subclinical hypothyroidism is controversial. We aimed to determine whether levothyroxine provided clinical benefits in older persons with this condition. Methods We conducted a double-blind, randomized, placebo-controlled, parallel-group trial involving 737 adults who were at least 65 years of age and who had persisting subclinical hypothyroidism (thyrotropin level, 4.60 to 19.99 mIU per liter; free thyroxine level within the reference range). A total of 368 patients were assigned to receive levothyroxine (at a starting dose of 50 μg daily, or 25 μg if the body weight was <50 kg or the patient had coronary heart disease), with dose adjustment according to the thyrotropin level; 369 patients were assigned to receive placebo with mock dose adjustment. The two primary outcomes were the change in the Hypothyroid Symptoms score and Tiredness score on a thyroid-related quality-of-life questionnaire at 1 year (range of each scale is 0 to 100, with higher scores indicating more symptoms or tiredness, respectively; minimum clinically important difference, 9 points). Results The mean age of the patients was 74.4 years, and 396 patients (53.7%) were women. The mean (±SD) thyrotropin level was 6.40±2.01 mIU per liter at baseline; at 1 year, this level had decreased to 5.48 mIU per liter in the placebo group, as compared with 3.63 mIU per liter in the levothyroxine group (P<0.001), at a median dose of 50 μg. We found no differences in the mean change at 1 year in the Hypothyroid Symptoms score (0.2±15.3 in the placebo group and 0.2±14.4 in the levothyroxine group; between-group difference, 0.0; 95% confidence interval [CI], -2.0 to 2.1) or the Tiredness score (3.2±17.7 and 3.8±18.4, respectively; between-group difference, 0.4; 95% CI, -2.1 to 2.9). No beneficial effects of levothyroxine were seen on secondary-outcome measures. There was no significant excess of serious adverse events prespecified as being of special interest. Conclusions Levothyroxine provided no apparent benefits in older persons with subclinical hypothyroidism. (Funded by European Union FP7 and others; TRUST ClinicalTrials.gov number, NCT01660126 .).

Concepts: Clinical trial, Thyroid-stimulating hormone, Hypothyroidism, Hashimoto's thyroiditis, Hyperthyroidism, Thyroid, Thyroid hormone, Placebo

83

 To estimate the effectiveness and safety of thyroid hormone treatment among pregnant women with subclinical hypothyroidism.

Concepts: Childbirth, Prolactin, Thyroid disease, Constipation, Hypothyroidism, Hyperthyroidism, Thyroid, Thyroid hormone

29

Several reports have suggested that propylthiouracil (PTU) may be safer than methimazole (MMI) for treating thyrotoxicosis during pregnancy because congenital malformations have been associated with the use of MMI during pregnancy.

Concepts: Developmental biology, Hyperthyroidism, Congenital disorder, Centers for Disease Control and Prevention, Congenital disorders, Methimazole, Congenital, Congenital abnormality

28

AIMS: Understanding the exact relationship between serum thyrotropin/thyroid stimulating hormone (TSH) and free thyroxine (FT(4)) is a prerequisite for improving diagnostic reliability and clinical decision making. METHODS: We (1) retrospectively studied the relationship between TSH and FT(4) in a large unselected clinical sample (n=6641) of primary hypothyroid, euthyroid and hyperthyroid subjects, and (2) applied a mathematical model of thyroid hormone feedback control to assess the relation between structural parameters and TSH levels in the different functional states. RESULTS: When separately analysing total sample and untreated subjects, the correlation slope for logTSH versus FT(4) for hypothyroid subjects was significantly different from that of the euthyroid panel and hyperthyroid subjects (the latter being compromised by reaching the TSH assay’s lower detection limit). As trends between functional states changed, each functional segment appeared to become differently regulated. Theoretical modelling and sensitivity analysis revealed that the influence of various structural parameters on TSH levels also depends on the overall function of the feedback loop. CONCLUSIONS: Our data suggest that the states of hypothyroidism, euthyroidism and hyperthyroidism can be regarded as differently regulated entities. The apparent complexity could be replicated by mathematical modelling suggesting a hierarchical type of feedback regulation involving patterns of operative mechanisms unique to each condition. For clinical purposes and assay evaluation, neither the standard model relating logTSH with FT(4), nor an alternative model based on non-competitive inhibition can be reliably represented by a single correlation comparing all samples for both hormones in one all-inclusive group.

Concepts: Physics, Thyroid-stimulating hormone, Thyroid disease, Hypothyroidism, Hyperthyroidism, Thyroid, Thyroid hormone, Triiodothyronine

28

A serum metabonomic profiling method based on ultra-performance liquid chromatography/time-of-flight mass spectrometry (UHPLC/TOF-MS) was applied to investigate the metabolic changes in hypothyroid rats induced by propylthiouracil (PTU). With Significance Analysis of Microarray (SAM) for classification and selection of biomarkers, 13 potential biomarkers in rat serum were screened out. Furthermore, Ingenuity Pathway Analysis (IPA) was introduced to deeply analyze unique pathways of hypothyroidism that were primarily involved in sphingolipid metabolism, fatty acid transportation, phospholipid metabolism and phenylalanine metabolism. Our results demonstrated that the metabonomic approach integrating with IPA was a promising tool for providing a novel methodological clue to systemically dissect the underlying molecular mechanism of hypothyroidism.

Concepts: Amino acid, Nutrition, Fatty acid, Triglyceride, Fat, Lipid, Hyperthyroidism, Fatty acid synthase