New Insights into the Hypothalamic-Pituitary-Thyroid Axis

Duntas, Leonidas H.

doi:10.4183/aeb.2016.125

Cited by 4 publications

(5 citation statements)

References 27 publications

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“…Blood concentrations of fT 4 and fT 3 are maintained within a narrow range, which remains constant throughout life with little intra-individual variability ( 1 , 2 ). This constancy probably reflects an individual’s pituitary “set point” ( 3 ). This close relationship is important because of the wide array of physiological activities that thyroid hormones influence.…”

Section: Introductionmentioning

confidence: 99%

Thyroid testing in acutely ill patients may be an expensive distraction

Premawardhana

2017

Biochemia Medica

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In health, an efficient negative feedback mechanism maintains serum thyroid hormone concentrations within an exquisitely controlled narrow range. Therefore any change that occurs to thyroid hormones in intrinsic thyroid disease is concordant and easy to interpret. Optimal functioning of the many tissues they influence is thereby facilitated. The situation in acute illnesses is different. Mechanisms that operate in these circumstances influence the hypothalamic-pituitary-thyroid axis and its components producing thyroid test results, which are discordant, do not fit recognizable patterns and are difficult to interpret. The yield of abnormalities is also low (about 7%). As many studies indicate, thyroid tests are expensive and consume large amounts of the hospital budget and resources of hospital laboratories. Other studies have shown that when abnormalities are detected, clinicians do not intervene or follow up these subjects. Therefore the clinical utility of thyroid testing in acutely ill patients is debatable. Interventions to change requestor behaviour with regard to thyroid testing in acutely ill subjects and the success of some audit and educational interventions are worthy of note. Thyroid testing in acutely ill patients is often an expensive distraction and is of limited clinical value. Targeted thyroid testing should be offered in this group only to those with: (a) symptoms or signs of thyroid disease e.g. goiter or orbitopathy; (b) risk factors for thyroid disease, previous or family history of thyroid disease; (c) taking drugs which potentially affect thyroid function e.g. thyroxine replacement therapy, amiodarone, lithium, mechanistic target of rapamycin (mTOR) inhibitors, interferon, alemtuzumab etc; (d) unexplained tachydysrhythmias.

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Section: Introductionmentioning

confidence: 99%

Thyroid testing in acutely ill patients may be an expensive distraction

Premawardhana

2017

Biochemia Medica

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“…Thyroid hormones (TH), which include thyroxine (T4) and triiodothyronine (T3), play important roles in early development, growth, and metabolism in vertebrates. TH synthesis and secretion are controlled by the hypothalamus‐pituitary axis 36 . Thyroid‐stimulating hormone, a glycoprotein secreted by the pituitary gland, acts on thyroid follicular cells and controls the synthesis and secretion of TH 37 .…”

Section: Discussionmentioning

confidence: 99%

“…TH synthesis and secretion are controlled by the hypothalamus-pituitary axis. 36 Thyroid-stimulating hormone, a glycoprotein secreted by the pituitary gland, acts on thyroid follicular cells and controls the synthesis and secretion of TH. 37 Thyrotropinreleasing hormone (TRH) is a tripeptide synthesized by the hypothalamus and acts on the pituitary gland to regulate the secretion of thyroid-stimulating hormone.…”

Section: Bpaf Exposure Affects Thyroid Function In Marine Medaka Embryosmentioning

confidence: 99%

Toxic effects of bisphenol AF on the embryonic development of marine medaka (Oryzias melastigma)

Huang

Gao

Chen

et al. 2023

Environmental Toxicology

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Bisphenol AF (BPAF), an emerging environmental endocrine disruptor, has been detected in surface waters worldwide and has adverse effects on aquatic organisms. The accumulation of BPAF in oceans and its potential toxic effect on marine organisms are important concerns. In this study, the effects of BPAF (10, 100, 1, and 5 mg/L) on marine medaka (Oryzias melastigma) were evaluated, including effects on the survival rate, heart rate, hatchability, morphology, and gene expression in embryos. The survival rate of marine medaka embryos was significantly lower after treatment with 5 mg/L BPAF than in the solvent control group. Exposure to 1 mg/L and 5 mg/L BPAF significantly reduced hatchability. Low‐dose BPAF (10 μg/L) significantly accelerated the heart rate of embryos, while high‐dose BPAF (5 mg/L) significantly decreased the heart rate. BPAF exposure also resulted in notochord curvature, pericardial edema, yolk sac cysts, cardiovascular bleeding, and caudal curvature in marine medaka. At the molecular level, BPAF exposure affected the transcript levels of genes involved in the thyroid system (dio1, dio3a, trhr2, tg, and thra), cardiovascular system (gata4, atp2a1, and cacna1da), nervous system (elavl3 and gap43), and antioxidant and inflammatory systems (sod, pparβ, and il‐8) in embryos. These results indicate that BPAF exposure can alter the expression of functional genes, induce abnormal development, and reduce the hatching and survival rates in marine medaka embryos. Overall, BPAF can adversely affect the survival and development of marine medaka embryos, and BPAF may not be an ideal substitute for BPA.

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“…The classical feedback regulation of the HPT axis is the primary mechanism for chronically maintaining the circulating free TH levels within the physiological range ( 15 ). The TSH-releasing hormone (TRH) is synthesized as a neurohormone in the paraventricular nucleus (PVN) of the hypothalamus.…”

Section: Introduction - Homeostatic Regulation Of Thyroid Hormonesmentioning

confidence: 99%

Intrathyroidal feedforward and feedback network regulating thyroid hormone synthesis and secretion

Zhang

2022

Front. Endocrinol.

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Thyroid hormones (THs), including T4 and T3, are produced and released by the thyroid gland under the stimulation of thyroid-stimulating hormone (TSH). The homeostasis of THs is regulated via the coordination of the hypothalamic-pituitarythyroid axis, plasma binding proteins, and local metabolism in tissues. TH synthesis and secretion in the thyrocytes-containing thyroid follicles are exquisitely regulated by an elaborate molecular network comprising enzymes, transporters, signal transduction machineries, and transcription factors. In this article, we synthesized the relevant literature, organized and dissected the complex intrathyroidal regulatory network into structures amenable to functional interpretation and systems-level modeling. Multiple intertwined feedforward and feedback motifs were identified and described, centering around the transcriptional and posttranslational regulations involved in TH synthesis and secretion, including those underpinning the Wolff-Chaikoff and Plummer effects and thyroglobulin-mediated feedback regulation. A more thorough characterization of the intrathyroidal network from a systems biology perspective, including its topology, constituent network motifs, and nonlinear quantitative properties, can help us to better understand and predict the thyroidal dynamics in response to physiological signals, therapeutic interventions, and environmental disruptions.

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New Insights into the Hypothalamic-Pituitary-Thyroid Axis

Cited by 4 publications

References 27 publications

Thyroid testing in acutely ill patients may be an expensive distraction

Thyroid testing in acutely ill patients may be an expensive distraction

Toxic effects of bisphenol AF on the embryonic development of marine medaka (Oryzias melastigma)

Intrathyroidal feedforward and feedback network regulating thyroid hormone synthesis and secretion

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