The Transient Human Thyroid Progenitor Cell: Examining the Thyroid Continuum from Stem Cell to Follicular Cell

The development of the thyroid follicular cell has been well characterized as it progresses from the original stem cell, either embryonic or adult, through a series of transitions to form a differentiated and functional thyroid cell. In this review, we briefly outline what is known about this transitional process with emphasis on characterizing the thyroid progenitor stem cell by using data obtained from both in vitro and in vivo studies and both mouse and human cells. It is of particular importance to note the influence of independent factors that guide the transcriptional control of the developing thyroid cell as it is subjected to extracellular signals, often working via epigenetic changes, and initiating intrinsic transcriptional changes leading to a functional cell. Thyroid stem cells fall into the category of dispositional stem cells and are greatly influenced by their environment.