Hypoprolactinemia can result from autoimmune disease, hypopituitarism, growth hormone deficiency, hypothyroidism, excessive dopamine action in the tuberoinfundibular pathway and/or the anterior pituitary, and ingestion of drugs that activate the D receptor, such as direct D receptor agonists like bromocriptine and pergolide, and indirect D receptor activators like amphetamines (through the induction of dopamine release).

Guidelines for diagnosing hypoprolactinemia are defined as prolactin levels below 3 µg/L in women, and 5 µg/L in men.