Urocortins (Ucns), peptides belonging to the corticotropin-releasing hormone (CRH) family, are classified into Ucn1, Ucn2, and Ucn3. They are involved in regulating several body functions by binding to two G protein-coupled receptors: receptor type 1 (CRHR1) and type 2 (CRHR2). In this review, we provide a historical overview of research on Ucns and their receptors in the mammalian endocrine system. Although the literature on the topic is limited, we focused our attention particularly on the main role of Ucns and their receptors in regulating the hypothalamic-pituitary-adrenal and thyroid axes, reproductive organs, pancreas, gastrointestinal tract, and other tissues characterized by "diffuse" endocrine cells in mammals. The prominent function of these peptides in health conditions led us to also hypothesize an action of Ucn agonists/antagonists in stress and in various diseases with its critical consequences on behavior and physiology. The potential role of the urocortinergic system is an intriguing topic that deserves further in-depth investigations to develop novel strategies for preventing stress-related conditions and treating endocrine diseases.

Cryptorchidism is the most common disorder of the sexual development in dogs, occurring in 13% of the males. Unilateral cryptorchidism is more frequent than bilateral and the right testis seems to be more frequently affected. Urocortin (UCN) is a corticotrophin-releasing hormone (CRH)-related peptide which was observed to affect several functions in male genital organs. The aim of the present study was to investigate the expression of UCN, and its receptors CRHR1 and CRHR2 by immunohistochemistry, Western blot and real-time RT-PCR in the normal and cryptic testis of the dog. The results showed that UCN, CRHR2 and CRHR1 were expressed in normal and cryptic testes. UCN-immunoreactivity (IR) was distributed in germ cells of the normal and cryptic testis. In the normal testis, CRHR2-IR was found in germ and interstitial Leydig cells. In the cryptic testis CRHR2-IR was distributed in gonocytes and interstitial Leydig cells. CRHR1-IR was distributed in the vessel smooth musculature and peritubular myoid cells. UCN and CRHR2 mRNA expression levels were lower in the cryptic than in normal testes. These results suggest that UCN and its receptors might play a role in regulating the spermatogenesis and hormonal activity of interstitial Leydig cells of the dog testis.