Advances in TRH signaling

Abstract

The activity of the hypothalamus-pituitary-thyroid axis (HPT) is coordinated by hypophysiotropic thyrotropin releasing hormone (TRH) neurons present in the paraventricular nucleus of the hypothalamus. Hypophysiotropic TRH neurons act as energy sensors. TRH controls the synthesis and release of thyrotropin, which activates the synthesis and secretion of thyroid hormones; in target tissues, transporters and deiodinases control their local availability. Thyroid hormones regulate many functions, including energy homeostasis. This review discusses recent evidence that covers several aspects of TRH role in HPT axis regulation. Knowledge about the mechanisms of TRH signaling has steadily increased. New transcription factors engaged in TRH gene expression have been identified, and advances made on how they interact with signaling pathways and define the dynamics of TRH neurons response to acute and/or long-term influences. Albeit yet incomplete, the relationship of TRH neurons activity with positive energy balance has emerged. The importance of tanycytes as a central relay for the feedback control of the axis, as well as for HPT responses to alterations in energy balance, and other stimuli has been reinforced. Finally, some studies have started to shed light on the interference of prenatal and postnatal stress and nutrition on HPT axis programing, which have confirmed the axis susceptibility to early insults.

A journey from brain to muscle across the thyroid continent

“…1 (backed by a 1,187-word long legend) of the Joseph-Bravo et al article [11], and the first two figures (backed by legends for a total of over 520 words) of the Sun et al article [10]. Noteworthy, 28.5% of the citations concern papers published in the last 5 years (2012-2016), with a remarkable 17.7% pertaining to the last 3 years (2014-2016).…”

“…Fresh stuff, indeed, and hats off to the authors! From this viewpoint, two articles stand out, namely the article by Ieni et al [6] and the one by Joseph-Bravo et al [11]. The former [6] features 86% of its references published during 2012-2016 and 64% in 2014-2016, while the corresponding numbers of the latter are and 38% and 43% [11].…”

“…From this viewpoint, two articles stand out, namely the article by Ieni et al [6] and the one by Joseph-Bravo et al [11]. The former [6] features 86% of its references published during 2012-2016 and 64% in 2014-2016, while the corresponding numbers of the latter are and 38% and 43% [11]. I wonder whether the journal should change its name from Reviews in Endocrine and Metabolic Disorders to Recent Evidence in Metabolic and endocrine Disorders, a novel denomination that would maintain the acronym REMD.…”

“…The journey begins in the top part of the body, visiting and getting to know new transcription factors engaged in TRH gene expression and signaling pathways that define the dynamics of TRH neurons' response to acute and/or long-term influences [11]. Along the journey, we will see the importance of tanycytes as a central relay for the feedback control of the hypothalamus-pituitary-thyroid (HPT) axis, and HPT responses to alterations in energy balance, and other stimuli.…”

“…Along the journey, we will see the importance of tanycytes as a central relay for the feedback control of the hypothalamus-pituitary-thyroid (HPT) axis, and HPT responses to alterations in energy balance, and other stimuli. As professional tour guides, Joseph-Bravo et al [11] are equipped with a powerful torch to let us see the interference of maternal and postnatal stress and nutrition on HPT axis programming. Thus, we can appreciate the susceptibility of the HPT axis to early insults, including the devastating effects of the endocrine disruptors.…”