The molecular biology of thyrotroph pituitary neuroendocrine tumors.

Pituitary neuroendocrine tumors (PitNETs), which were formerly known as pituitary adenomas, are classified in 5th Edition of the WHO Classification of Endocrine and Neuroendocrine Tumors. Since thyrotroph PitNETs are rare PitNETs, most previous studies about former thyroid stimulating hormone (TSH)-secreting pituitary adenoma have focused on a small number of cases. However, the diagnostic rate of thyrotroph PitNET has increased because of increased sensitivity of serum TSH measurement and widespread recognition that thyrotroph PitNETs are the cause of syndrome of inappropriate secretion of TSH (SITSH). Therefore, knowledge on the molecular mechanism of thyrotroph PitNET is gradually accumulating. Recently, comprehensive chromosomal, genetic, and epigenomic alterations in thyrotroph PitNET have been revealed with the availability of comprehensive gene and protein analyses, and the nature of thyrotroph PitNET is gradually being elucidated. However, further analysis is needed to determine whether the causes of these changes are directly responsible for the development of tumors.