RESUMEN
<p><b>BACKGROUND</b>Cushing's disease (CD) presents a remarkable preponderance in female gender, and a significant minority of patients with CD presented with negative magnetic resonance imaging (MRI) findings. The aim of this study was to evaluate gender-related and MRI classification-related differences in clinical and biochemical characteristics of CD.</p><p><b>METHODS</b>We retrospectively studied 169 patients with CD, comprising 132 females and 37 males, and 33 patients had no visible adenoma on MRI.</p><p><b>RESULTS</b>We observed that male and MRI-positive patients presented with high adrenocorticotropic hormone (ACTH) values (P < 0.05). Female patients presented with higher prevalence of hirsutism and hyperpigmentation and lower prevalence of purple striae (P < 0.05). The prevalence of buffalo-hump and hypertension was greater in MRI-negative patients (P < 0.05). In addition, male patients with CD presented at a younger age compared with females (P < 0.05). Patients with fatigue and hypokalaemia presented significantly higher urinary-free cortisol, ACTH and cortisol levels compared with patients without these symptoms (P < 0.05). The prevalence of LH reduction, hyper total cholesterol (TC) and hyper low-density lipoprotein was more frequent in MRI-positive patients (P < 0.05). Hyper-TC levels and PRL reduction were more frequent in males (P < 0.05). T3, T4 and FT3 levels negatively correlated with age at diagnosis (r = -0.310, P < 0.01; r = -0.191, P < 0.05; r = -0.216, P < 0.05). T3, T4, FT3 and FT4 levels significantly negatively correlated with 8-am plasma cortisol levels (r = -0.328, P < 0.01; r = -0.195, P < 0.05; r = -0.333, P < 0.01; r = -0.180, P < 0.05). Females presented higher total protein level (P < 0.01) and lower blood urea nitrogen and serum creatinine levels (P < 0.01), compared with male patients.</p><p><b>CONCLUSIONS</b>Carefulness and caution are required in all patients with CD, because of the complexity of clinical and biochemical characteristics in CD patients of different gender and MRI classification, particularly male patients and MRI-negative patients.</p>