5-Hydroxyindoles and the Thyroid

Publisher Summary This chapter discusses the role of 5-hydroxyindoles on thyroid gland. It presents a link between the morphology, histogenesis, and function of parafollicular cells with medullary carcinoma of the thyroid. It is suggested (1) that the lateral thyroid anlage plays a significant role in the development of the human thyroid, and that some of its derivatives persist throughout life; (2) that some cells from the lateral thyroid anlage give rise to the parafollicular system, which differs in morphology and function from the follicular. This cell system is able to concentrate 5-HTP and has a high content of 5-HT together with its enzymes of synthesis and degradation, 5-HTP decarboxylase and monoamine oxidase (MAO); (3) that medullary carcinoma of the thyroid is a tumor of parafollicular cells. It is associated with a clinical syndrome of watery diarrhea and may be associated with a raised 5-HIAA excretion; and (4) that the morphology, histogenesis, and function of medullary carcinoma distinguish it from other types of thyroid carcinoma.