Magnetic Resonance Imaging Measurements of Pituitary Stalk Compression and Deviation in Patients with Nonprolactin-Secreting Intrasellar and Parasellar Tumors

Abstract

Prolactin (PRL) Levels are frequently elevated in patients with non-PRL-secreting adenomas or other intrasellar and parasellar diseases ("pseudoprolactinomas"). This phenomenon is believed to result from a loss of dopaminergic inhibition on pituitary lactotrophs and is known as the "stalk-section effect." Using magnetic resonance imaging scans and a high-magnification sella technique, we measured a number of parameters indicative of the disruption of normal sellar structures. The investigator was blind to the patient's diagnosis and PRL level while collecting the data. Parameters measured were the tumor size, the angular deviation of the pituitary stalk, and the degree of compression of the pituitary stalk. Measurements were obtained from 44 patients with pathologically confirmed tumors that had no immunohistochemical reactivity to PRL. PRL levels were often higher than expected. Four patients (9%) had a PRL level of more than 150 ng/ml, and three patients (7%) had a PRL level of 200 ng/ml or more. One patient with a plasmacytoma eroding the sella floor had a PRL level as high as 504 ng/ml. There was no significant correlation of PRL level and the degree of pituitary stalk compression, stalk deviation, or tumor size. PRL levels were found to be markedly elevated in some patients with a tumor causing little distortion of the pituitary stalk. Conversely, PRL levels were often normal despite evidence of massive distortion of the stalk. Therefore, magnetic resonance imaging evidence of pituitary stalk distortion cannot be used to determine the diagnosis of prolactinoma versus pseudoprolactinoma in most cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnostic pitfalls of hyperprolactinemia: the importance of sequential pituitary imaging

“…According to the previous reports, mild hyperprolactinemia, which is considered non-definitive concentration between prolactinoma and non-functioning pituitary adenoma, were defined as 90 – 200 ng/ml [8, 10, 11]. The patients with serum prolactin concentration in this range were considered as border zone cases.…”

Masked hyperprolactinemia: Tumor-derived factors inhibiting prolactin secretion caused by pituitary-stalk damage

“…Secondary hyperprolactinemia has conventionally been explained as the result of pituitary stalk damage; however, this theory remains controversial. 6,7 Given that there are competing theories, and that the results of the present study suggest otherwise, it may be profitable for us to rethink our understanding of the mechanism underlying the induction of secondary hyperprolactinemia. Based on our present findings, we propose that pituitary stalk damage alone cannot fully account for the induction of secondary hyperprolactinemia.…”

“…1 However, there are few published studies that support this theory, 1,5 and some that contradict it. 6,7 To date, the pathogenesis of secondary hyperprolactinemia remains poorly understood.…”

“…1,[5][6][7] It is possible that secondary hyperprolactinemia is influenced not only by extrasellar factors but also by intrasellar factors, including the autocrine or paracrine effects of pituitary tumors. In the present study we investigated possible extrasellar factors radiographically by using MRI (tumor size and extension morphology) and endocrinologically by monitoring the hormonal function of the pituitary gland during the insulin-induced hypoglycemia (IIH) test.…”

Sellar Toxoplasmosis and Nonfunctioning Pituitary Adenoma

“…PRL levels caused by this effect do not seem to correlate with tumor size, stalk deviation, or the degree of stalk compression (6,21). In prolactinoma, there is a correlation between PRL levels and tumor size with macroprolactinoma (>10 mm in diameter) typically being associated with PRL levels >250 mg/L (12,17,22).…”