Available online 20 July 2022, 101018

The pituitary is a very plastic organ.

Hormone production and cell number are both adjusted to fit the demands.

In the mammalian and fish pituitary, there are cells producing multiple hormones.

New endocrine cells originate from three different mechanisms.

Differences between fish and mammals might reflect the lack of studies in fishes.

The vertebrate pituitary is a dynamic organ, capable of adapting its hormone secretion to different physiological demands. In this context, endocrinologists have debated for the past 40 years if endocrine cells are mono or multi-hormonal. Since its establishment, the dominant “one cell, one hormone” model has been continuously challenged. In mammals, the use of advanced multi-staining approaches, sensitive gene expression techniques, and the analysis of tumor tissues have helped to quickly demonstrate the existence of pituitary multi-hormone cells. In fishes however, only recent advances in imaging and transcriptomics have enabled the identification of such cells. In this review, we first describe the history of the discovery of cells producing multiple hormones in mammals and fishes. We discuss the technical limitations that have led to uncertainties and debates. Then, we present the current knowledge and hypotheses regarding their origin and biological role, which provides a comprehensive review of pituitary plasticity.

pituitary

endocrine

hormone

plasticity

fish

teleost

mammals

multi-hormonal cell

proliferation

transdifferentiation

hypophysis

© 2022 The Author(s). Published by Elsevier Inc.