Corticotropin-releasing hormone
Corticotropin-releasing hormone (CRH) (also known as corticotropin-releasing factor (CRF) or corticoliberin; corticotropin may also be spelled corticotrophin) is a peptide hormone involved in stress responses. It is a releasing hormone that belongs to corticotropin-releasing factor family. In humans, it is encoded by the CRH gene.[5] Its main function is the stimulation of the pituitary synthesis of adrenocorticotropic hormone (ACTH), as part of the hypothalamic–pituitary–adrenal axis (HPA axis).
Corticotropin-releasing hormone (CRH) is a 41-amino acid peptide derived from a 196-amino acid preprohormone. CRH is secreted by the paraventricular nucleus (PVN) of the hypothalamus in response to stress. Increased CRH production has been observed to be associated with Alzheimer's disease and major depression,[6] and autosomal recessive hypothalamic corticotropin deficiency has multiple and potentially fatal metabolic consequences including hypoglycemia.[5]
In addition to being produced in the hypothalamus, CRH is also synthesized in peripheral tissues, such as T lymphocytes, and is highly expressed in the placenta. In the placenta, CRH is a marker that determines the length of gestation and the timing of parturition and delivery. A rapid increase in circulating levels of CRH occurs at the onset of parturition, suggesting that, in addition to its metabolic functions, CRH may act as a trigger for parturition.[5]
A recombinant version for diagnostics is called corticorelin (INN).
The 41-amino acid sequence of CRH was first discovered in sheep by Vale et al. in 1981.[29] Its full sequence is:
The rat and human peptides are identical and differ from the ovine sequence only by 7 amino acids.[30]
Role in non-mammalian vertebrates[edit]
In mammals, studies suggest that CRH has no significant thyrotropic effect. However, in representatives of all non-mammalian vertebrates, it has been found that, in addition to its corticotropic function, CRH has a potent thyrotropic function, acting with TRH to control the hypothalamic–pituitary–thyroid axis (TRH has been found to be less potent than CRH in some species).[31][32]
