Prolactin as a marker of successful catheterization during IPSS in patients with ACTH-dependent Cushing's syndrome.
BACKGROUND
Anomalous venous drainage can lead to false-negative inferior petrosal sinus sampling (IPSS) results. Baseline inferior petrosal sinus to peripheral (IPS/P) prolactin ratio higher than 1.8 ipsilateral to the highest ACTH ratio has been proposed to verify successful catheterization. Prolactin-normalized ACTH IPS/P ratios may differentiate Cushing's disease (CD) from ectopic ACTH syndrome (EAS).


OBJECTIVE
Our objective was to examine the utility of prolactin measurement during IPSS.


METHODS
We conducted a retrospective analysis of prolactin levels in basal and CRH-stimulated IPSS samples in ACTH-dependent Cushing's syndrome (2007-2010).


RESULTS
Twenty-five of 29 patients had a pathologically proven diagnosis (17 CD and eight EAS). IPSS results were partitioned into true positive for CD (n = 16), true negative (n = 7), false negative (n = 1), and false positive (n = 1). Prolactin IPS/P ratio suggested successful IPSS in eight of 11 with abnormal venograms. Baseline prolactin IPS/P ratio was helpful in two patients with abnormal venograms and false-negative (catheterization unsuccessful) or true-negative (catheterization successful) IPSS results; the normalized ratio correctly diagnosed their disease. Normalized ACTH IPS/P ratio was at least 1.3 in all with CD, but prolactin IPS/P ratios were misleadingly low in two. One patient with cyclic EAS had a false-positive IPSS when eucortisolemic (baseline prolactin IPS/P = 1.7; normalized ratio = 5.6). All other EAS patients had normalized ratios no higher than 0.7.


CONCLUSIONS
Prolactin measurement and evaluation of the venogram can improve diagnostic accuracy when IPSS results suggest EAS but is not necessary with positive IPSS results. Confirmation of hypercortisolemia remains a prerequisite for IPSS. A normalized ratio of 0.7-1.3 was not diagnostic.
Program on Reproductive and Adult Endocrinology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Sharma
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Raff
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Nieman
D000182:ACTH Syndrome, Ectopic / Q000097:blood / Q000175:diagnosis*; D000328:Adult; D000368:Aged; D003480:Cushing Syndrome / Q000097:blood / Q000175:diagnosis*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017591:Petrosal Sinus Sampling / Q000379:methods*; D011388:Prolactin / Q000097:blood*; D012189:Retrospective Studies
D011388:Prolactin