parafolikulære

Parafollicular is a term used in biology and medicine to describe structures or cells that are located adjacent to or around a follicle. The most common context for this term is in relation to hair follicles, where parafollicular cells might refer to specific cells in the skin surrounding the hair follicle. These cells can play a role in the follicle's growth cycle, immune response, or signaling pathways.

Another significant use of the term "parafollicular" is in the context of the thyroid gland. Here, it refers to parafollicular cells, also known as C cells. These cells are distinct from the follicular cells that produce thyroid hormones. Parafollicular cells are responsible for synthesizing and secreting calcitonin, a hormone that plays a role in calcium and phosphate metabolism by lowering blood calcium levels. In histological examinations of thyroid tissue, the location and appearance of these parafollicular cells are important for diagnosing various thyroid conditions, including C-cell hyperplasia and medullary thyroid carcinoma. The precise arrangement and density of parafollicular cells can provide diagnostic clues.