Thyroid follicles

In life, many people suffer from endocrine disorders due to bad living and eating habits, which leads to thyroid diseases. In fact, there are many factors that lead to thyroid diseases. Among the many complications of thyroid diseases, thyroid follicles are relatively common. Normal people may also experience such symptoms, but many people do not understand this symptom very well. Let us take a look at what thyroid follicles are.

The follicle is composed of a single layer of thyroid follicular epithelial cells, which is a bubble-like structure filled with gelatinous fluid. The diameter of the follicles is 0.02 to 0.9 mm and they are round, oval or irregular in shape. The morphology of follicular epithelial cells and the amount of follicular visceral fluid are closely related to their functional status.

Normally, follicular epithelial cells are cuboidal. When the thyroid gland is functioning well, the cells become taller and columnar, cell division can be seen, and the amount of gelatinous fluid in the follicles decreases. When the thyroid gland is underactive, the follicular epithelial cells become shorter and flatter, and the amount of jelly-like fluid increases. The gelatinous fluid in the follicles is thyroglobulin, which is eosinophilic and homogeneously stained. The PAS reaction is positive, indicating that it is a glycoprotein secreted by follicular epithelial cells.

Main Function

It enhances the body's heat metabolism, promotes the absorption of sugar by the small intestine, and participates in the regulation of fat metabolism. In addition, it can also promote the development and maturation of tissues and organs, especially the brain and bones. Therefore, in childhood, hypothyroidism can cause cretinism.

Parafollicular cells

Parafollicular cells, also known as C cells, accumulate in clusters between follicles, with a small number embedded between follicular epithelial cells. Their luminal surface is covered by follicular epithelium. The cells are relatively large in size, and their cytoplasm is slightly lighter in HE-stained specimens. The silver plating method revealed argyrophilic granules in the basal cytoplasm, which contained calcitonin and were secreted by exocytosis.

Calcitonin is a polypeptide that lowers blood calcium by promoting osteoblasts to secrete osteoid, calcium salt deposition and inhibiting the dissolution of calcium in bones. It has been reported that mammalian parafollicular cells also contain somatostatin, norepinephrine, substance P and vasoactive intestinal peptide.

The morphology, size, number and distribution of parafollicular cells vary with the species of animal. The parafollicular cells of humans, monkeys, mice, etc. are oval and distributed in small cell groups between follicles. In contrast, the parafollicular cells of animals such as cats and dogs are round or oval in shape and accumulate between the follicles to form large cell clusters. In humans, parafollicular cells are mostly distributed in the thyroid gland around the parathyroid glands, while in mice, they are mostly distributed in the central part of the thyroid gland.