Prolactin Excess and Deficiency: Epidemiology, Causes (Excluding Prolactin-Secreting Pituitary Tumors)

Abstract

Prolactin excess, defined as an increase of serum prolactin above the laboratory reference limit, is a frequent problem in endocrine practice. It affects females predominantly, but occurs in both males and females. Although in many situations hyperprolactinemia is physiological (pregnancy, lactation, nipple stimulation, or stress), it can be the consequence of a pathological condition or a drug. Any situation leading to a decreased dopaminergic inhibition of prolactin secretion or to a reduction of prolactin clearance can cause hyperprolactinemia. Psychotropic drugs, like antipsychotics or some antidepressants, are among the most frequently reported etiologies. However, occasionally the cause of prolactin excess remains unknown, and these cases are diagnosed as idiopathic hyperprolactinemias. Prolactin deficiency refers to decreased or absent serum levels of prolactin due to a loss of function of lactotroph pituitary cells. Epidemiological data of prolactin deficiency are scarce because of a relative perceived lack of clinical significance compared with other pituitary hormones. Isolated prolactin deficiency is rare; most patients have evidence of other pituitary hormone deficiencies. Sheehan’s syndrome, which usually presents with inability to breastfeed, is one of the most recognized causes of hypoprolactinemia. Finally, although prolactin disorders are mostly acquired, a genetic etiology may be possible and has to be investigated.