Approach to the Patient With Dopamine-Resistant Microprolactinoma

Prolactinoma is a significant cause of hyperprolactinemia and the most common type of pituitary tumor. Women of fertile age are most commonly affected, and the clinical picture is characterized by galactorrhea, oligo-amenorrhea, and infertility. In microprolactinomas, which represent more than 60% of cases in women before menopause, there is usually no concern about the mass effect. Therefore, management can be expectant if there are no symptoms or in a patient in the postmenopausal period; oral contraceptive in the presence of hypogonadism and no desire for pregnancy; dopamine agonist (DA) in the presence of bothersome galactorrhea, hypogonadism, and the desire for fertility; and neurosurgery in selected noninvasive cases. Resistance to DA occurs in less than 10% of cases. Although the reduction in dopamine receptor subtype 2 expression is considered the primary cause of DA resistance, the underlying mechanisms are not yet completely elucidated. The main concern in resistant cases is the risk of symptomatic tumor growth during assisted reproduction techniques and pregnancy. Other conditions in which hyperprolactinemia could be implicated, such as metabolic parameters, osteoporosis, and breast cancer risk are also discussed. Understanding the mechanisms of DA resistance can lead to the opening of new treatment strategies.