Endocrine Abstracts

One of the major routes for metabolism of thyroid hormones is by deiodination through the iodothyronine deiodinases, an enzyme family consisting of three members, types 1 (D1), 2 (D2) and type 3 (D3). The outer ring of thyroxin (T4) can be deiodinated by D2, leading to the formation of active hormone, triiodothyronine (T3). D2 is expressed predominantly in the brain and pituitary, but also in brown adipose tissue and muscle. Within the cell, D2 is localiz...

During illness changes in thyroid hormone metabolism occur, collectively known as the non-thyroidal illness syndrome (NTIS). NTIS is characterized by low serum thyroid hormone levels, while TSH and TRH expression do not increase, indicating a disturbance of the normal thyroid hormone feedback regulation.Although the common view was that NTIS results in overall downregulation of metabolism in order to save energy, recent work has shown that genes involved...

The “sick euthyroid syndrome” or “non-thyroidal illness syndrome” (NTIS) occurs in a large proportion of hospitalized patients and comprises a variety of alterations in the hypothalamus-pituitary-thyroid (HPT) axis that are observed during illness. One of the hallmarks of NTIS is decreased plasma triiodothyronine (T3) levels, in severe illness accompanied by low plasma thyroxine (T4) and increased plasma reverse T3 (rT3) concentrations. Downregulation of hy...

During illness changes in thyroid hormone metabolism occur, collectively known as the non-thyroidal illness syndrome (NTIS). NTIS is characterized by low serum thyroid hormone levels, while TSH and TRH expression do not increase, indicating a disturbance of the normal thyroid hormone feedback regulation.Although the common view was that NTIS results in overall downregulation of metabolism in order to save energy, recent work has shown that genes involved...

Background: Previously, we showed that thyroid hormone (TH) supplementation reduced hepatosteatosis in patients with non-alcoholic fatty liver disease (NAFLD) and was more effective in older patients. We hypothesized that intrahepatic TH concentrations may decrease with age. To investigate this issue, we examined the effects of age on intrahepatic TH concentrations in a mouse model of NAFLD.Methods: Intrahepatic TH levels and deiodinase activity were mea...

Thyroid hormone levels are strongly affected by inflammation. In a wide spectrum of diseases, ranging from critical illness in the ICU to ischemic stroke, a decrease in circulating T3 and T4 is observed without the expected increase in TSH. This disruption of the negative feedback system of the hypothalamic–pituitary–thyroid (HPT) axis is accompanied by various changes in thyroid hormone metabolism at the cellular and tissue level. C...

Resistance to thyroid hormone due to a mutation in thyroid hormone receptor alpha (RTHα) is a syndrome whose features include delayed growth and neurocognitive development. Macrophages, which derive from circulating monocytes and have recently been recognized as important thyroid hormone target cells, are innate immune cells that are capable of adopting a wide range of phenotypes. Assuming the right phenotype in the right setting is crucial as macrophage dysfunction has b...

Introduction: Physicians in our hospital notified the laboratory staff of a number of patients at the outpatient clinic with increased free T4 (fT4) concentrations without (complete) suppression of thyroid stimulating hormone (TSH). This phenomenon appeared to occur more frequently following implementation of a new automated fT4 immunoassay. The discordance between fT4 and TSH concentrations may be explained by analytical issues (not further explained here), incorrect referenc...

Fasting induces profound metabolic changes in order to decrease energy expenditure and to conserve energy. One of the major adaptations is downregulation of the hypothalamus–pituitary–thyroid (HPT) axis, characterized by decreased serum thyroid hormone levels without an increase in serum TSH or in TRH expression in the hypothalamic paraventricular nucleus (PVN). Leptin has been proposed as a critical signal initiating the neuroendocrine response to fasting as it decr...

Inactivation of the thyroid hormone transporters Mct8/Oatp1c1 in mice causes a profound TH deficiency in the CNS due to an impaired TH transport across brain barrier cells. As oligodendrocyte maturation and myelin formation requires proper thyroid hormone (TH) signaling, Mct8/Oatp1c1 double knock-out (DKO) mice exhibit a persistent state of hypomyelination similar to the situation in MCT8 deficient patients. Yet, to which extent proper myelination is dependent on the presence ...