Pituitary glycoprotein hormone receptors in non-endocrine organs

Although glycoprotein hormones are usually regarded as pituitary–endocrine signals, their receptors can be found in non-endocrine tissues. High expression of selected receptors in the pituitary–endocrine axis is key to mammalian endocrine regulation. We hypothesize that peripheral receptor distribution during development and in secondary organs reflects older but still-applicable functions, with their concentration in the pituitary a more recent evolutionary advancement. We extrapolate additional functions of these receptors by analogy of homologous receptors in older phyla, with emphasis on the bony fishes (teleosts). Studies of the multiple roles of the glycoprotein hormone receptors are likely to uncover novel endocrine functions and axes, and highlight the potential of these receptors as novel therapeutic targets.