Neurophysins are carrier proteins which transport the hormones oxytocin and vasopressin to the posterior pituitary from the paraventricular and supraoptic nucleus of the hypothalamus, respectively. Neurophysins are secreted from the hypothalamus along with their passenger hormones. It appears the neurophysins are parts of the precursor molecules. They are secreted from the posterior pituitary with their associated hormone (in the case of vasopressin, a glycopeptide is also secreted). The functions of the secreted neurophysin is unknown.
There are two types:
References
Neurophysins Wikipedia(Text) CC BY-SA