The thyroid gland consists of follicles producing triiodothyronine (T3) and tetraiodothyronine or thyroxine (T4). As a second endocrine element, the thyroid contains clear cells dispersed solitarily or in small groups in and between the epithelial walls of the follicles. These cells, called parafollicular cells or C cells (from clear cells), are the source of the blood calcium level-lowering hormone, calcitonin (reviews: Nunez and Gershon 1978b; Ericson and Sundler 1984).
KeywordsSecretory Granule Follicular Cell Thyroid Follicular Cell Parafollicular Cell Neuroectodermal Origin
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