Clinical and Radiographic Characteristics Related to Hyperprolactinemia in Nonfunctioning Pituitary Adenomas

Hyperprolactinemia in patients with nonfunctioning pituitary adenomas (NFPAs) has been explained by the stalk compression of large pituitary adenomas. However, not all large NFPAs are associated with high serum prolactin levels. We aimed to elucidate and compare clinical, hormonal, and radiographic characteristics of NFPAs with and without hyperprolactinemia.

We included 201 patients with clinically NFPAs who underwent transsphenoidal surgery performed by a single surgeon during 2010-2017 at a single center in Korea. We measured the three-dimensional diameters (anteroposterior [AP], width, height) and volumes of NFPA on magnetic resonance imaging. We conducted morning basal hormone measurements and dynamic tests preoperatively and 3 months postoperatively.

All NFPAs were macroadenomas, and mean tumor volume was 10.4 ± 7.7 cm³. Of 201 patients, 59 (29.4%) had preoperative hyperprolactinemia. Hormone recovery rate was higher in patients with hyperprolactinemia compared with patients without hyperprolactinemia after age, sex, body mass index, tumor volume, and gross total resection adjustments (odds ratio [95% confidence interval]: 2.55 [1.10-5.92]). Tumor width/AP diameter ratio positively correlated with serum prolactin levels (r = 0.186, P = 0.008). Tumor volume was not significantly different between the 2 groups.

Preoperative prolactin level is a useful marker to predict hormone recovery after surgery. Patients with NFPA and hyperprolactinemia tended to have a higher width/AP diameter ratio. Hyperprolactinemia of NFPA is more likely affected by tumor growth pattern, such as width/AP diameter ratio, than tumor volume.