What is the thyroid gland?

The thyroid gland is the largest endocrine gland of the human body, with the main function of regulating metabolism. However, it affects every organ, ensuring a multitude of functions, from normal brain development to energy consumption and heat production.

To perform these functions, the thyroid gland receives orders from the pituitary gland through thyroid stimulating hormone (TSH), and indirectly from the hypothalamus through thyroid releasing hormone (TRH), forming the hypothalamic-pituitary-thyroid axis, which controls the function of the thyroid gland. Its name comes from its shape (“thyreos”, ancient Greek word for “shield”).

Anatomically, it is located in the middle of the neck, just below the larynx, and microscopically it consists of two types of cells with different function and origin: the follicular cells, which originate from the foregut and are responsible for the production of thyroid hormones (T3 and T4) and the parafollicular cells, which produce calcitonin (involved in bone and calcium metabolism) and have neuroendocrine origin.