Thyroid Microcirculation
John H. Barker, Gary L. Anderson, Michael D. Menger in Clinically Applied Microcirculation Research, 2019
In addition to an important role in the thyroidal iodide presentation rate, thyroid blood flow would also serve to deliver thyrotropin (thyroid stimulating hormone) to this gland. As the name implies, thyrotropin is an important regulator of thyroid follicular cell function and virtually all of the activities of thyroid follicular cells can be affected by this pituitary hormone. The presentation rates of tropic hormones to other endocrine organs (e.g., the ovary and adrenal) have been postulated to be one mechanism whereby glandular function is modulated.16–18 However, to date it is unresolved whether such a phenomenon occurs in the thyroid gland. Observations that the exogenous administration of vasoactive peptides, at doses known to affect thyroid blood flow, do not appear to alter thyrotropin-induced responses do not support this possibility.19,20
Screening for phenylketonuria and congenital hypothyroidism
Micha de Winter, Mariëlle Balledux, José de Mare, Ruud Burgmeijer in Screening in Child Health Care, 2018
‘In principle there are three forms of CHT. In the most frequently seen form, primary CHT (approximately 93% of all CHT cases in the Netherlands), the cause lies in the thyroid gland. Primary CHT is characterized by the combination of low thyroxine and high thyrotropin values. In 1988, the prevalence of primary CHT was 1:3700 and in 1989, 1:2800. Both values show a great similarity to other Western countries (1:3000–1:4000)’ (Verkerk & Vaandrager 1990b). In the other two forms of CHT, secondary and tertiary CHT, (together approximately 7% of all CHT cases in the Netherlands) the cause is not the thyroid gland itself, but the inadequate stimulation of the thyroid gland by the regulating centres (the hypophysis and hypothalamus). Here low thyroxin values are found while the thyrotropin values are not raised (Meijer 1984). In its annual report for 1989, the National Committee for CHT Monitoring (Landelijke Begeleidingscommissie CHT) (LBC-CHT) (Verkerk & Vaandrager 1990b) observes with respect to the prevalence of secondary/tertiary CHT that ‘the number of patients with secondary/tertiary CHT is three, this is 1:63,000 live births. This prevalence is lower than that found in previous years. Vulsma (1991) and others report a prevalence of 1:26,000 for the period January 1981 up to and including September 1989. In addition to chance fluctuations, the fact that a significant proportion of these patients (26%) are not identified during screening plays a role.’
Neoplasia in pregnancy
Hung N. Winn, Frank A. Chervenak, Roberto Romero in Clinical Maternal-Fetal Medicine Online, 2021
Diagnosis is often made by palpation, but must be confirmed by biopsy. FNA has been shown to be a safe and effective technique in pregnant women, with false-positive results being exceedingly rare and false-negative results occurring in only 5% to 10% of cases (252). Some advocate fine-needle aspiration of all thyroid nodules prior to 20 weeks of gestation, and after 20 weeks, only those that grow during suppressive therapy should be sampled (264). Radioisotope nuclear scanning is contraindicated in pregnancy, because radioactive isotopes are taken up by the fetus. Other methods, such as ultrasound, can be used to distinguish solid-form cystic nodules. Thyroid function tests may also be helpful and can diagnose unsuspected thyroiditis. If medullary thyroid cancer is suspected, a calcitonin level should be checked as well. Normally, pregnancy witnesses a hypertrophy of the thyroid gland from follicular cell hyperplasia, and total triiodothyronine and thyroxine levels are elevated while triiodothyronine resin uptake is decreased secondary to increased thyroid-binding globulin. Thyroid-stimulating hormone is in the normal to slightly elevated range.
The Role of TPOAb in Thyroid-Associated Orbitopathy: A Systematic Review
Published in Ocular Immunology and Inflammation, 2022
Georgios Kyriakos, Alexandros Patsouras, Errika Voutyritsa, Christos Gravvanis, Eirini Papadimitriou, Paraskevi Farmaki, Lourdes Victoria Quiles-Sánchez, Vasiliki E. Georgakopoulou, Christos Damaskos, Antonio Ríos-Vergara, Luis Marín-Martínez, Evangelos Diamantis
Considering the association between TAO and thyroid dysfunction, the presence of anti-thyroid antibodies is believed to play a role in the pathogenesis and clinical status of TAO patients. The most commonly reported thyroidal antibodies are antithyroid peroxidase (TPOAb), antithyroglobulin (TgAb), and anti-thyrotropin receptor antibodies (TRAb).8 Specifically, TRAb levels showed the greatest association with TAO.9 The thyrotropin receptor is expressed not only in the thyroid follicular cells but also in the orbital fibroblasts.10 The autoimmunity directed against the receptor on orbital tissues induces infiltration of inflammatory cells, hyaluronic acid accumulation, and the orbital adipose tissue expansion, which eventually leads to the remodeling of orbital connective tissues and fibrosis in its final stage.11 However, there are still some limitations regarding its clinical use, as these antibodies are not present in all cases.12
Determination of age and sex specific TSH and FT4 reference limits in overweight and obese individuals in an iodine-replete region: Tehran Thyroid Study (TTS)
Published in Endocrine Research, 2021
Hengameh Abdi, Bita Faam, Safoora Gharibzadeh, Ladan Mehran, Maryam Tohidi, Fereidoun Azizi, Atieh Amouzegar
The relationship between thyroid function and body weight in euthyroid individuals has been considered in the literature1–3 and positive association of serum thyroid-stimulating hormone (TSH) with body weight has been reported.4,5 Leptin, a hormone produced by white adipose cells, has an important role in the regulation of thyroid function through its effect on the thyrotropin-releasing hormone (TRH) expression in the hypothalamus.6 On the other hand, TSH receptors of adipose cells and cellular signals transferred by activating the cAMP-dependent kinase pathway result in adipocyte precursor differentiation in adipocytes and lipogenesis.7 Since multiple pituitary hormone receptors are expressed in adipose tissue, the possible “hypothalamic-pituitary-adipocyte axis” has been hypothesized.8
Thyroid Feedback Quantile-based Index correlates strongly to renal function in euthyroid individuals
Published in Annals of Medicine, 2021
Sijue Yang, Shuiqing Lai, Zixiao Wang, Aihua Liu, Wei Wang, Haixia Guan
The secretion of thyroid hormone is regulated by hypothalamic-pituitary-thyroid (HPT) axis. Thyrotropin-releasing hormone (TRH) from the hypothalamus promotes the synthesis and release of TSH from the anterior pituitary, which plays an important role in all stages related to the production and secretion of thyroid hormones from the thyroid gland. The levels of TRH and TSH are in turn modulated by the negative feedback of thyroid hormones. Thyroid hormones are mainly secreted in the form of T4, which is catalyzed by deiodinases to form the bioactive T3. Both will bind to carrier proteins in the circulation and enter cells via membrane transporters. T3 then further binds to the nuclear thyroid hormone receptors. Therefore, thyroid function is regulated by the HPT axis and other factors associated with thyroid hormone conversion and bioactivity [26].
Related Knowledge Centers
- Anterior Pituitary
- Triiodothyronine
- Glycoprotein
- Thyroid
- Levothyroxine
- Pituitary Gland
- Hypothalamus
- Hypothalamic–Pituitary Hormone
- Thyrotropic Cell
- Thyrotropin-Releasing Hormone