Subnormal prolactin responsiveness to thyrotropin-releasing hormone (TRH) in women with primary empty sella syndrome

Basal prolactin (PRL) levels and PRL responsiveness to thyrotropin-releasing hormone (TRH) were studied in 10 women with primary empty sella (PES) syndrome (mean age 38.2 yr). Hyperprolactinemia (34 to 72 ng/ml) was found in 5 patients (hyperprolactinemic PES, H-PES), whereas 5 patients showed normal (9.5 to 19 ng/ml) PRL levels (normoprolactinemic PES, N-PES). The results were compared with those obtained in 10 healthy women (mean age 32.8 yr, PRL = 7 to 15 ng/ml) and in 8 women with a PRL-secreting pituitary microadenoma (MA) (mean age 37.5 yr, PRL = 39 to 85 ng/ml). The mean basal levels of PRL were significantly higher in patients with H-PES (50.8 +/- 13.2 ng/ml) or MA (64.0 +/- 18.3 ng/ml) than in the control group (10.9 +/- 2.6 ng/ml, p less than 0.02) and in the patients with N-PES (13.9 +/- 3.7 ng/ml, p less than 0.02). In contrast, the relative maximum response (RMR) of PRL to TRH (peak PRL/basal PRL) was significantly lower in the patients with PES (both H-PES and N-PES) or MA (1.4 +/- 0.4, 2.3 +/- 0.7 and 1.2 +/- 0.2, respectively) than in the control subjects (3.6 +/- 1.1; p less than 0.02, less than 0.05 and less than 0.02, respectively). Our results show that the pituitary responsiveness to the acute stimulation with TRH is significantly decreased both in patients with a PRL-secreting pituitary MA and in those with PES. Therefore, the clinical value of the TRH test in distinguishing the PES syndromes from prolactinomas seems to be questionable.