The neurohypophysial hormones form a
family
Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
of structurally and functionally related
peptide hormones. Their representatives in humans are
oxytocin
Oxytocin is a peptide hormone and neuropeptide normally produced in the hypothalamus and released by the posterior pituitary. Present in animals since early stages of evolution, in humans it plays roles in behavior that include Human bonding, ...
and
vasopressin. They are named after the location of their release into the blood, the
neurohypophysis (another name for the posterior pituitary).
Most of the circulating oxytocin and vasopressin hormones are synthesized in
magnocellular neurosecretory cells of the
supraoptic nucleus and
paraventricular nucleus of the hypothalamus. They are then transported in neurosecretory granules along axons within the
hypothalamo-neurohypophysial tract by
axoplasmic flow to
axon terminals forming the pars nervosa of the posterior pituitary. There, they are stored in
Herring bodies
Herring bodies or neurosecretory bodies are structures found in the posterior pituitary. They represent the terminal end of the axons from the hypothalamus, and hormones are temporarily stored in these locations. They are neurosecretory termin ...
and can be released into the circulation on the basis of hormonal and synaptic signals with assistance from
pituicytes.
Oxytocin mediates contraction of the
smooth muscle of the uterus and mammary gland, while vasopressin has
antidiuretic action on the kidney, and mediates vasoconstriction of the peripheral vessels.
Due to the similarity of the two hormones, there is cross-reaction: oxytocin has a slight antidiuretic function, and high levels of
AVP can cause uterine contractions.
In common with most active peptides, both hormones are synthesised as larger protein precursors that are enzymatically converted to their mature forms.
Members of this family are found in birds, fish, reptiles and amphibians (mesotocin, isotocin, valitocin, glumitocin, aspargtocin, vasotocin, seritocin, asvatocin, phasvatocin), in worms (annetocin, nematocin), octopuses (cephalotocin, octopressin), insects (locupressin, inotocin) and in molluscs (conopressins G and S).
Animals that ''lack'' a hormone from this family include fruit flies, and at least some mosquitos, silkworms, and honeybees.
References
{{InterPro content, IPR000981
Protein families
Hormones
Peptides