In the comprehensive review of hyperprolactinemia by Omar Serri and associates1 the answers to some important questions remain unclear.
Fig. 2 of the article recommends MRI of the pituitary if pathologic hyperprolactinemia is identified on repeat measurement of prolactin, but there is no definition of what constitutes pathologic hyperprolactinemia. It appears that the authors are suggesting MRI of the pituitary if the prolactin level remains elevated on repeat measurement, but what extent of elevation should lead to consideration of MRI? For example, should the physician perform imaging studies if the prolactin level is marginally elevated but still less than 100 μg/L? In clinical practice, patients with marginally elevated levels on 2 or 3 occasions often undergo imaging studies of the pituitary gland, but is this practice justified? Consideration of MRI of the pituitary is one of the most important clinical decision-making points in the management of hyperprolactinemia, so it would be helpful to have some guidance in this regard.
In addition, to what extent does nipple or breast stimulation cause elevation in prolactin levels, and how long should the patient avoid such stimulation before the repeat measurement of prolactin is performed?
Turning to the causes of this condition, Fig. 1 of the article lists anti-ulcer agents, specifically H2 antagonists, as medications causing elevation of prolactin levels. However,2 other medications, metoclopramide and domperidone2 (motility agents commonly used in patients with gastroesophageal reflux), are dopamine antagonists and are more likely than H2 antagonists to cause elevated prolactin levels. These drugs should be considered as causative agents and should be discontinued before further investigations are undertaken.
Malvinder S. Parmar Medical Director, Internal Medicine Timmins and District Hospital Timmins, Ont.