Thyroid and Parathyroid Imaging
George H. Gass, Harold M. Kaplan in Handbook of Endocrinology, 2020
The perchlorate ion, like the pertechnetate ion, is trapped in thyroid tissue but not organified.80 If administered in pharmacological quantities perchlorate will compete with iodine for thyroidal trapping.80 This has been exploited to detect defects of iodide organification when 1 g of potassium perchlorate is administered (children 3 mg/kg body weight) 2 h after the radioiodine dose.80 In normal subjects there is no change in the count rate over the thyroid before and after perchlorate administration, but in a positive test the count rate falls by at least 10% in conditions of congenital inborn errors of organification or acquired diseases such as Hashimoto’s thyroiditis.80 This test remains useful in determining the etiology of goitrous hypothyroidism in children and families, particularly where associated with deafness (Pendred’s syndrome).80
Imaging of the thyroid gland
Pallavi Iyer, Herbert Chen in Thyroid and Parathyroid Disorders in Children, 2020
I-123 is a radiotracer with a half-life of 11 hours, making it ideal for diagnostic purposes. It is used to assess NIS-regulated function of the thyroid gland and iodide coupling and organification (DUOX2–TPO) needed for thyroid hormone synthesis. Defects in organification caused by dyshormonogenesis would result in the I-123 tracer being “washed out” easily by perchlorate discharge. The test involves administering I-123 and measuring uptake 2 hours post-administration. One hour later, an oral perchlorate is administered and another thyroid uptake image is obtained. With no organification defect, the perchlorate is unable to displace the I-123 that has been organified, but if the perchlorate rapidly displaces the I-123 (greater than 5–10% decrease in uptake), then a defect in an organification step is suspected.
Biochemical and Pharmacological Rationales in Radiotracer Design
Lelio G. Colombetti in Principles of Radiopharmacology, 2019
The oldest and classical example of the biochemical approach is the use of isotopes of iodine for imaging the thyroid gland. Iodide ion is actively accumulated in the follicular colloid where it is predominantly converted to iodine by iodinase and incorporated into thyroid hormones. Myers110 reviewed the nuclear characteristics of the radioisotopes of iodine and suggested that isotopes with mass numbers of 121, 123, 125, 126, 128, 129, and 131 could have diagnostic applications. Of these, 131I (half-life of 8 days) and 125I (half-life of 60 days) are the most frequently used clinically. A number of radionuclides other than iodine are accumulated by the thyroid gland but do not undergo organification. Technetium-99m as pertechnate ion is an example and has been used for thyroid scanning. More recently, iodine-131 has also been used in the diagnosis of functional metastases of thyroid carcinoma in the liver.111,112
Excess iodine-induced lymphocytic impairment in adult rats
Published in Toxicology Mechanisms and Methods, 2019
Adipa Saha, Sandip Mukherjee, Ankita Bhattacharjee, Deotima Sarkar, Arijit Chakraborty, Arnab Banerjee, Amar K. Chandra
Iodine is found in trace amount in the human body at low concentration (15–25 mg), mostly in the thyroid gland (Hays 2001). It is an essential component of thyroid hormones (T4 and T3). Thyroid gland actively uptakes iodine, followed by its organification as formation of iodized compounds; these compounds are then used for synthesis of thyroid hormone which regulates a number of metabolic functions and promotes normal growth, development, and maturation of many organs including brain. The level of iodine intake and the occurrence of thyroid diseases is ‘U’ shaped indicating that there is an increased risk with both low and high iodine intake (Laurberg et al. 2001). For normal thyroid hormone synthesis as well as for normal thyroid function an adequate amount of iodine intake is essential. Inadequate intake of dietary iodine leads to an adaptation mechanism that includes insufficient intrathyroidal iodine, preferential synthesis and secretion of T3 as appeared to decrease T4 secretion resulting in increased secretion of thyroid stimulating hormone (TSH) that ultimately leads to enlargement of thyroid gland (goiter) and associated iodine deficiency disorders (IDDs). On the other hand, excessive intake of dietary iodine may cause thyroid dysfunction as iodine-induced hyperthyroidism, hypothyroidism or goiter. In addition, excess iodine aggravates thyroid autoimmune reactions resulting in autoimmune thyroid diseases (AITDs).
Modeling principles of protective thyroid blocking
Published in International Journal of Radiation Biology, 2022
Alexis Rump, Stefan Eder, Cornelius Hermann, Andreas Lamkowski, Manabu Kinoshita, Tetsuo Yamamoto, Junya Take, Michael Abend, Nariyoshi Shinomiya, Matthias Port
Although the three-compartment model described above should be considered as very useful for practical purposes, the disposition of inorganic and organic iodine seems to be actually more complex. This led to the development of models using several interconnected compartments to represent the thyroid permitting to better understand iodine trapping by organification in the gland (Hays 1978). A more elaborate biokinetic model including additional tissue compartments and an exchange with the gastrointestinal tract that was originally developed by Leggett (2010) was meanwhile adopted by the ICRP (2017). For the sake of completeness, it should be mentioned that other models intended for special subpopulations have been developed, e.g. to describe the age-dependent iodine disposition in children (Leggett 2017) or in pregnant or breastfeeding women, including the possibility to assess the dose absorbed by the thyroid of the embryo/fetus depending on the gestational age or the nursing infant (Berkovski 2002).
An innovative approach to polycystic ovary syndrome
Published in Journal of Obstetrics and Gynaecology, 2022
Mariano Bizzarri, Patrizia Logoteta, Giovanni Monastra, Antonio Simone Laganà
The research carried out by Unfer on inositols started from MI in PCOS and reproduction disorders and then opened innovative ways, also far beyond the PCOS therapy, in areas hitherto little or nothing explored in connection with MI or MI/DCI in the 40:1 ratio. Now we very briefly mention his studies on the use of MI in combination with oral contraceptive pill, achieving the goal to reduce the dose of the contraceptive pill (Minozzi et al. 2011) or in combination with melatonin (Vitale et al. 2016) to improve the outcome of IVF (Unfer et al. 2011b, Carlomagno et al. 2011a, Carlomagno et al. 2018). Furthermore, he tested MI in gestational diabetes mellitus (GDM), obtaining interesting results (Costabile and Unfer 2017), confirmed by other groups (Santamaria et al. 2016; Fraticelli et al. 2018; Pintaudi et al. 2018; Santamaria et al. 2018; Celentano et al. 2020). Finally, he highlighted the usefulness of MI to regulate iodine organification and thyroid hormone biosynthesis. This MI effect may increase thyroid functionality and possibly allow a quicker recovery from iodine deficiency (Barbaro et al. 2019).
Related Knowledge Centers
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