The embryology of the parathyroid glands, the thymus and certain associated rudiments

Gilmour, J. R.

doi:10.1002/path.1700450304

Cited by 167 publications

(63 citation statements)

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“…IET is an old entity, first described in 1937 by Gilmour. He reported a fetus with the thymus buried within thyroid and an instance of thymus in a similar location in an infant [11]. Parathyroid glands also have a similar embriyologic origin, and in fact there have been rare cases of IET accompanying or surrounding intrathyroidal parathyroid gland [12,13].…”

Section: Discussionmentioning

confidence: 99%

Intrathyroidal ectopic thymus in children: a sonographic survey

et al. 2017

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Aims: Intrathyroidal ectopic thymus (IET) is being increasingly reported in the radiology literature. Most of the reports are of individual cases or small series and prevalence and natural course of the pathology is not well known. The purpose of this study is to establish the prevalence of IET in children and report long term follow-up results.Material and methods: In 180 children who were examined by ultrasound (US) for other reasons, 7 patients were indentified with IET. Together with the other seven children who were already under follow-up for IET (diagnosed using US criteria), these 14 patients were followed up with US for 30 months. Size, shape, location, echotexture and internal echoes of the lesions were evaluated.Results: There were 16 lesions in 14 children. The most common appearance was a fusiform hypoechoic lesion, with punctate and linear internal echoes and well-defined but slightly irregular borders located posteriorly in the lower thirds of the thyroid. In follow-up, there were no changes in echotexture, shape or border. In 3 patients, the lesion became slightly smaller, in a 10-year-old boy slightly larger, and in an 11-year old boy the lesion disappeared. In a patient with bilateral lesions, one lesion slightly decreased in size.Conclusions: IET in children may be more common than thought. Its growth reflects that of a normal thymus. Awareness of this entity is important in order not to misdiagnose them, especially as papillary cancer, and to prevent unnecessary interventions.

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Section: Discussionmentioning

confidence: 99%

Intrathyroidal ectopic thymus in children: a sonographic survey

et al. 2017

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“…In humans, parathyroids and thymus share a common developmental origin within the third pharyngeal pouch, while a second pair of parathyroids originate from the fourth pouch (56,222,518,669). As in the animal models, the friable nature of developing parathyroids leads to thymic and other ectopic locations for fragments that detach during embryonic migration.…”

Section: Human Datamentioning

confidence: 99%

Bone Development and Mineral Homeostasis in the Fetus and Neonate: Roles of the Calciotropic and Phosphotropic Hormones

Kovacs

2014

Physiological Reviews

211

188

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Mineral and bone metabolism are regulated differently in utero compared with the adult. The fetal kidneys, intestines, and skeleton are not dominant sources of mineral supply for the fetus. Instead, the placenta meets the fetal need for mineral by actively transporting calcium, phosphorus, and magnesium from the maternal circulation. These minerals are maintained in the fetal circulation at higher concentrations than in the mother and normal adult, and such high levels appear necessary for the developing skeleton to accrete a normal amount of mineral by term. Parathyroid hormone (PTH) and calcitriol circulate at low concentrations in the fetal circulation. Fetal bone development and the regulation of serum minerals are critically dependent on PTH and PTH-related protein, but not vitamin D/calcitriol, fibroblast growth factor-23, calcitonin, or the sex steroids. After birth, the serum calcium falls and phosphorus rises before gradually reaching adult values over the subsequent 24 -48 h. The intestines are the main source of mineral for the neonate, while the kidneys reabsorb mineral, and bone turnover contributes mineral to the circulation. This switch in the regulation of mineral homeostasis is triggered by loss of the placenta and a postnatal fall in serum calcium, and is followed in sequence by a rise in PTH and then an increase in calcitriol. Intestinal calcium absorption is initially a passive process facilitated by lactose, but later becomes active and calcitriol-dependent. However, calcitriol's role can be bypassed by increasing the calcium content of the diet, or by parenteral administration of calcium.

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“…These small clusters, and often single cells, are not identifiable by conventional histology and were only revealed by high resolution in situ hybridization studies. These cells are present in both mice and humans (Phitayakorn and McHenry, 2006;Liu et al, 2010), and can be located anywhere along the path of thymus migration as well as embedded within the thymus; these trailing parathyroid cells are excellent candidates for being the source of supernumerary or accessory parathyroid glands, which are frequently seen in humans (Weller, 1933;Gilmour, 1937;Norris, 1938;Van Dyke, 1959). The misplaced parathyroid cells that remain attached to the thymus were shown to be the source of thymus-associated secreted PTH in mice; the thymus itself was also shown to express PTH, but as a self-antigen only for negative selection (and not under the control of Gcm1 or Gcm2) and not contributing to serum PTH (Liu et al, 2010).…”

Section: Thymus-parathyroid Connections: Shared Functions?mentioning

confidence: 99%

Mechanisms of thymus organogenesis and morphogenesis

2011

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The thymus is the primary organ responsible for generating functional T cells in vertebrates. Although T cell differentiation within the thymus has been an area of intense investigation, the study of thymus organogenesis has made slower progress. The past decade, however, has seen a renewed interest in thymus organogenesis, with the aim of understanding how the thymus develops to form a microenvironment that supports T cell maturation and regeneration. This has prompted modern revisits to classical experiments and has driven additional genetic approaches in mice. These studies are making significant progress in identifying the molecular and cellular mechanisms that control specification, early organogenesis and morphogenesis of the thymus.

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The embryology of the parathyroid glands, the thymus and certain associated rudiments

Cited by 167 publications

References 5 publications

Intrathyroidal ectopic thymus in children: a sonographic survey

Intrathyroidal ectopic thymus in children: a sonographic survey

Bone Development and Mineral Homeostasis in the Fetus and Neonate: Roles of the Calciotropic and Phosphotropic Hormones

Mechanisms of thymus organogenesis and morphogenesis

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