Diagnostic and Management Challenges of Prolactinomas; Dr. Marvin Bergsneider; SubSaharan African Grand Rounds

SUMMARY Dr. Marvin Bergsneider, who Co-Head of the Pituitary and Skull Base Surgery Section of Neurosurgery at UCLA discusses Pituitary tumors. For those of us who have forgotten pituitary physiology, all the 8 hormones related to the pituitary, come from control centers in the hypothalamus around the third ventricle. For the posterior pituitary, there are direct neural connections from the hypothalamus to the posterior pituitary for production of ADH (antidiuretic hormone) and oxytocin for lactation and uterine contractions. The Anterior pituitary is a collection of cells wrapped around the Posterior lobe embryologically from Rathke’s pouch. 5 different protein releasing factors originate from hypothalamus which stimulate the anterior lobe pituitary cells. The hormones produced by the 5 cell types in the pituitary gland control the thyroid, bone growth, liver and insulin production, adrenal and reproductive glands. The last hormone produced inhibits the production of Prolactin from the cells in the anterior lobe of the pituitary.

Tumors of these cells are called PitNET (Pituitary NeuroEndocrineTumors). All these target cells in the pituitary can form tumors, but the most common tumor site is from the prolactin producing cells. Prolactin producing cells make up 30% of pituitary tumors. Another 30% are clinically non-functional (CNF) tumors, all of which represent 20% of all the brain tumors. His talk and the discussion center on the prolactin producing cells which relate to lactation in the female and have limited clinical expression in the male, and how to distinguish them from CNF tumors.

There are many causes of hyperprolactinemia making the symptoms non-specific. In the male hyper-function of prolactin from tumors can present with erectile dysfunction or gynecomastia or from mass effect on the other hormone producing cells in the pituitary. Males usually are asymptomatic but can present late with symptoms. Females present with disturbed or absent menstruation, low libido, and/or abnormal lactation. Physicians have measured prolactin blood levels which in males can reach a high of 60 ng/ml, while in females it can be variable but is abnormal over 400 ng/ml. High levels of Prolactin are usually diagnostic of prolactinoma. The diagnostic difficulty comes with lower levels of prolactin. Dr. Bergsneider discusses the prolactin levels and sex differences in detail.

Cabergoline, a dopamine like agonist, is given to suppress the prolactin production in the pituitary cells and can shrink the tumor in 75% of patients. One third are cured with this biochemical treatment after a year. Persistence of hyper-prolactin levels occurs in the rest of the cases. Those who cannot tolerate the drug, should have surgery. In cases where the female wants pregnancy, Cabergoline must be stopped. Other reasons for surgery are mass effect and disruption of other pituitary function cells.

The explanation for the elevated prolactin levels in the past was attributed to the “Stalk Effect” or compression of the pituitary stalk. This compression prevented the hypothalamus produced Prolactin inhibiting factor (PIF) from traveling down the stalk to inhibit prolactin production at the cellular level. As a result, the uninhibited cells produce more Prolactin, leading to elevated Prolactin levels. This idea has now been replaced by the research that finds rising intra-sellar pressure from unrestricted tumor growth eventually causes other pituitary cells to dysfunction and failing pituitary hormonal production later in 85% of cases as the tumor enlarges. This is called the “Triphasic effect “ from Dr. Bergsneider’s research.

The tumor is grossly removed, endoscopically, with a high percentage of cure. Remnants can regrow; so complete removal is necessary. He shows an intra-operative video of his procedure and discusses the details of his surgery. Most places in the world can measure prolactin levels, but if that is not possible, treatment then relates to mass effect. Radiation can be used for resistant tumors. So, prolactin becomes a key to measuring the function of a large percentage of pituitary tumors. Tumors of the other pituitary gland cells can be tested for specific physiologic functions with their own specific treatments. After 100 years of work on pituitary tumors, little is still known about the origin of tumors in this small special area of the body with such a concentration of active cells at the base of the skull. How can we strop the growth of tumors in one cell line without effecting the others? Getting the specific tumor growth to stabilize metabolically or to regress by molecular treatment seems to be the most likely avenue of research to cure this disease without surgery. Does surgery make sense in the long term? From the SubSaharan African Grand Rounds. Excellent Talk; Common Problem; Video Excellent; Podcast Good but imaging helps. (Lecture 35 min Discussion 15 min). (JIA)