The major clinical feature of a prolactin deficiency is the inhibition of lactation in women. There are a number of factors that may cause this deficiency that include psychogenic and normal variants.
The most important cause that needs to be considered is hypopituitarism (caused by Sheehan's Syndrome). This is a condition where there is a postpartum necrosis of the pituitary gland. Other hormone deficiencies should be investigated in this case.