What is the pathophysiology of prolactinomas?

Updated: Mar 25, 2018
  • Author: Venkatesh Babu Segu, MD, MBBS, DM; Chief Editor: Romesh Khardori, MD, PhD, FACP  more...
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Answer

Tumor formation is due to neoplastic transformation of anterior pituitary lactotrophs, resulting in excess synthesis and secretion of prolactin (PRL). Linkage to aryl hydrocarbon-interacting protein gene (AIP) mutation has been identified in some families with prolactinoma and in childhood-onset pituitary adenomas. [6]

Physiologically, PRL, a polypeptide hormone consisting of 199 amino acids, is regulated by hypothalamic factors. These include prolactin-releasing factors (PRFs) and prolactin-inhibitory factors (PIFs).

Dopamine (DA) is the principal PIF, and thyrotropin-releasing hormone (TRH), vasoactive intestinal peptide, and peptide histidine methionine are the putative PRFs. The physiologic role of these PRFs is not established. A delicate balance between the PRFs and PIFs normally keeps the serum PRL level within a physiologic range. Moreover, the interplay of various neurohormonal factors results in a pulsatile secretion of PRL from the pituitary. Prolactinoma is one of the several causes of pathologic hyperprolactinemia. [2, 7, 8, 9, 10]

A retrospective study by Peng et al of 102 patients found that growth hormone deficiency and hypogonadism were the most frequent types of pituitary hormone dysfunction in adult males with prolactinomas, with hypocortisolism occurring less often. [11] This observation should come as no surprise, since prolactinomas in men are often larger (macroprolactinomas) and are thus likely to cause tissue compression, in contrast to prolactinomas in women, which are often small (microprolactinomas) at the time of initial diagnosis.


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