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Anatomy and Physiology of Head and Neck Endocrine Glands
Published in R James A England, Eamon Shamil, Rajeev Mathew, Manohar Bance, Pavol Surda, Jemy Jose, Omar Hilmi, Adam J Donne, Scott-Brown's Essential Otorhinolaryngology, 2022
Parathyroid lobules contain clusters of parenchymal cells surrounded by a fibrovascular stroma with a rich capillary network. The most prominent cell type is the chief (principal) cell; chief cells are responsible for production of parathyroid hormone (PTH). Larger and less prevalent are the oxyphil cells. The function of oxyphil cells is not well understood.
Imaging of the parathyroid gland
Published in Pallavi Iyer, Herbert Chen, Thyroid and Parathyroid Disorders in Children, 2020
The most common planar method, dual-phase single-isotope imaging, utilizes a single isotope, 99mTc sestamibi, over time to obtain multiple imaging phases. In dual-phase single-isotope imaging patients receive an intravenous injection of 99mTc sestamibi, which is concentrated intracellularly in mitochondria. An initial image is performed at 10–15 minutes and then again after 90 minutes to 3 hours. In the early phase, 99mTc sestamibi distributes to the parotid, submandibular, salivary glands, thyroid gland, heart, and liver. The prominence of mitochondria-rich oxyphil cells, parathyroid adenomas, and hyperplasic parathyroid glands result in retained 99mTc sestamibi. Due to the more rapid washout of 99mTc sestamibi from the thyroid gland than hyperfunctioning parathyroid glands, delayed imaging may identify abnormal parathyroid glands (Figure 10.2).
Thyroid Hormones and Calcium Metabolism
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
Parathyroid hormone (PTH) is produced by four small glands located at the superior and inferior poles of both lobes of the thyroid gland. The parathyroid gland contains two cell types, namely, the chief cells that secrete PTH and the oxyphil cells of unknown function.
Apoptosis in Primary Hyperparathyroidism
Published in Journal of Investigative Surgery, 2018
Oliwia Anna Segiet, Łukasz Mielańczyk, Adam Piecuch, Marek Michalski, Szczepan Tyczyński, Marlena Brzozowa-Zasada, Mariusz Deska, Romuald Wojnicz
The expression of TRAIL was enhanced in both MGD and PA [35–37]. A previous study has indicated higher number of positively stained for this factor cells in MGD compared to PA [35]. Nevertheless, another trial established raised reactivity in PA [36]. There were no differences in the immunopositivity for both Fas and TRAIL in chief cells and oxyphil cells [30, 35]. Chief cells are the most important cell types in parathyroid gland because of their role in endocrine system. They synthesize PTH, which is implicated in maintaining calcium level balance. Oxyphil cells are less numerous, larger and previously were thought to be only transdifferentiated and deactivated chief cells, which play only a supportive role. However, recent studies have revealed that oxyphil cells produce PTH, parathyroid hormone-related protein (PTHrP), calcitriol, calcium-sensing receptor (CaR), glial cells missing 2, vitamin D receptor (VDR), and 25-hydroxyvitamin D-1α-hydroxylase [42]. The presence of VDR and CaR implies that oxyphil cells synthesize PTH in a regulated manner. The number of these cells is significantly increased in secondary hyperparathyroidism caused by chronic kidney disease [42].
The Value of Preoperative and Intraoperative Ultrasound in the Localization of Intrathyroidal Parathyroid Adenomas
Published in Journal of Investigative Surgery, 2022
Wei Zhao, Ruigang Lu, Li Yin, Bojun Wei, Mulan Jin, Chun Zhang, Ruijun Guo, Xiuzhang Lv
Of the 13 IPAs in our study, 10 cases were positive on Tc-99m MIBI SPECT/CT, but only 5 cases showed suspicious intrathyroid parathyroid lesions. The reason is that normal thyroid or thyroid nodules also takes up this radioisotope, so it might be difficult to accurately detect abnormal parathyroid glands within the thyroid. 2 cases of complete IPA (the size were 0.9 × 0.7 × 0.4 cm and 1.0 × 0.5 × 0.4 cm) were negative in Tc-99m MIBI SPECT/CT with the preoperative serum calcium and serum PTH were 2.75 mmol/L and 166.6 pg/mL, 2.65 mmol/L and 111.6 pg/mL, respectively. The false negative on Tc-99m MIBI SPECT/CT is mainly related to the small size of parathyroid adenomas. In a research, Jones et al.18 showed that Sestamibi (MIBI) scintigraphy had a sensitivity of 93% for adenomas >500 mg, while sensitivity was 51% for adenomas <500 mg. The cellular composition of abnormal parathyroid nodules is also a factor that affecting the accuracy of 99mTc sestamibi scintigraphy. It was reported that 122 cases of parathyroid adenomas in Tc-99m MIBI SPECT/CT, 26 (38%) cases were false negatives in 68 adenomas composed predominantly of chief cells, while false negatives were also detected in 2 (9.0%) of 23 adenomas formed predominantly by oxyphil cells and in 8 (25.8%) of 31 mixed adenomas.19 In addition, other factors that may affect the detection rate of abnormal parathyroid lesions include the level of serum calcium, serum PTH and cystic degeneration of nodules. Sestamibi-SPECT, as a functional imaging mode for the parathyroid, is helpful for the diagnosis of parathyroid lesions, especially in the localization of ectopic adenoma. However, it has limited effectiveness in the preoperative location of lesions due to other factors leading to false negativity and its unsatisfactory ability to determine sectional anatomical information.