Faje A, Jones P, Swearingen B, Tritos NA. The prolactin per unit tumor volume ratio accurately distinguishes prolactinomas from secondary hyperprolactinemia due to stalk effect.
Endocr Pract 2022;
28:572-577. [PMID:
35339688 DOI:
10.1016/j.eprac.2022.03.013]
[Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 03/19/2022] [Accepted: 03/21/2022] [Indexed: 11/30/2022]
Abstract
OBJECTIVE
Prolactin levels alone are insufficient to distinguish between some cases of prolactinomas and stalk effect. We aimed to (i) formally characterize the relationship between serum prolactin and prolactinoma volume, (ii) determine a cutoff for prolactin/mm3 that accurately distinguishes prolactinomas from stalk effect, and (iii) validate this cutoff in a cohort selected to include ambiguous prolactin values ranging from 50-150 ng/ml.
METHODS
We utilized the Research Patient Database Registry and transsphenoidal surgery database in our institution to retrospectively identify adult patients with clinically nonfunctioning tumors (primary analysis n=279; validation cohort n=10) and prolactinomas (primary analysis n=94; validation cohort n=18). Solid tumor volumes were measured by Visage®7 software, and cystic foci within tumors were excluded.
RESULTS
Prolactin levels correlated strongly with prolactinoma volume (r2=0.801) but were not a relevant predictor of nonfunctioning tumor size (r2=0.015). Prolactin/mm3 values did not overlap between nonfunctioning tumors (median 0.016, interquartile range [IR] 0.009-0.028) and prolactinomas (median 0.551, IR 0.265-0.845), p<0.0001. A cutoff of 0.065 (ng/ml)/mm3 correctly discriminated between prolactinomas and nonfunctioning tumors in all 401 patients in the primary analysis and validation cohort.
CONCLUSIONS
The prolactin:volume ratio correctly distinguished all prolactinomas from stalk effect in this study, including a validation cohort specifically chosen for potential ambiguity. This study is the first formal volumetric analysis of prolactin secretion in pituitary adenomas, and our results suggest that measurement of prolactin/mm3 is a valuable tool to better characterize challenging cases of primary tumoral secretion versus secondary hyperprolactinemia due to stalk effect.
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