Endocrine Abstracts

Thyroid hormones (TH) regulate (brain) development, growth, body temperature, most pathways involved in energy and structural metabolism as well as anabolic and catabolic reactions. Inadequate availability of essential trace elements (iodine, selenium, iron, zinc) limits TH biosynthesis, metabolism and action. Endocrine-disrupting chemicals (EDC), i.e., exogenous chemicals or their mixtures, can interfere with any aspect of TH synthesis, distribution, transport, metabolism, an...

Thyroid hormone (TH) biosynthesis, storage and secretion is organized in a complex series of biochemical reactions round an evolutionary conserved functional unit, the thyroid follicle, a highly vascularised epithelial structure enclosing the colloidal lumen mainly composed of thyroglobulin (Tg). The luminal apical surface of this tight epithelial monolayer is the site of H2O2 dependent TH biosynthesis and is involved in mobilization of Tg, the colloidal ...

The endogenous decarboxylated thyroid hormone (TH) metabolite 3-Iodothyronamine (3-T1AM) exerts partially TH antagonistic effects in rodents and was shown to suppress the hypothalamic pituitary thyroid axis in rats after single dose application. Therefore, it might play a role in maintaining TH homoeostasis. Among the molecular targets of 3-T1AM are G protein-coupled receptors like the trace amine associated receptor 1 (TAAR1) and adrenergic receptors. Furthermore, 3-T1AM was ...

The endogenous thyroid hormone metabolite 3,5-diiodothyronine (3,5-T2) has attracted attention as a metabolically active substance modulating metabolism via classical thyroid hormone (TH) receptor-dependent and rapid plasma membrane, cytosolic and mitochondrial signaling pathways. Accordingly, 3,5-T2 has been proposed as a potential hypolipidaemic agent without inducing thyromimetic effects and is frequently used as illicit weight-reducing agent. The objective of the present s...

Thyroid hormone transport into cells critically depends on plasma membrane transport proteins. One of these, monocarboxylate transporter 8 (MCT8), is mutated in patients suffering from a form of X-linked mental retardation, the Allan-Herndon-Dudley syndrome. These patients are characterized by abnormal thyroid hormone and TSH plasma levels indicating a role for MCT8 in the regulation of the thyroid hormone axis. Mice lacking the Mct8 gene replicate the thyroid hormone a...

Iodine (I) and selenium (Se) are two essential trace elements for regular thyroid gland functioning and thyroid hormone metabolism. Most Europeans are only marginally supplied with both elements through their daily nutrition. The mammalian organism has developed efficient and highly complex mechanisms to control I and Se uptake, metabolism and recycling. The thyroid gland is equipped with the necessary transporters and metabolizing enzymes for I uptake and bioconversion into t...

Background: Selenoproteins contain the 21st proteinogenic amino acid selenocysteine (Sec) and exert important biological functions. Selenoprotein S (SelS) has only recently been identified and appears to be implicated in type 2 diabetes and inflammation. In vitro studies have shown that SelS expression is controlled by circulating cytokine and glucose levels. Mechanistically, SelS participates in the retro-translocation during quality control in the ER and the ER-associ...

Introduction: Besides the classical thyroid hormones T4 and T3 the endogenous thyroid hormone metabolite 3,5-diiodothyronine (3,5-T2) attracted attention during the last years due to its metabolic activity. 3,5-T2 exerts thyromimetic action on the hypothalamus-pituitary-thyroid axis and the heart as well as on energy and lipid metabolism. In previous liver transcriptome analyses of 3,5-T2-treated lean and diet-induced obese male mice, effects on hepatic lipid, steroid, xenobio...

Recent findings revealed 3,5-diiodo-L-thyronine (3,5-T2) as a metabolically active iodothyronine affecting hepatic energy and lipid metabolism. Therefore, 3,5-T2 has been proposed as a potential hypolipidemic agent for treatment of obesity and its hepatic aftermath. So far only limited data exists relating to the effects of 3,5-T2 on metabolism in euthyroid mammals maintained on high-fat diet from the day of weaning onwards. Therefore, we performed a study in wh...

Introduction: Patients in need of an intensive care unit (ICU) treatment due to severe diseases often develop the non-thyroidal illness syndrome (NTI). These critically ill patients present with low thyroxine (T4), low 3,3’,5-triiodothyronine (T3) and elevated reverse T3 (rT3) serum concentrations while TSH and 3,3’-diiodothyronine (3,3’-T2) concentrations remain unaffected. To further elucidate the underlying changes ...