PURPOSE: Increasing evidence exists that hyperprolactinemia alters metabolic profile. The mechanism of this effect is unknown. We aimed to investigate the differences between the metabolic profile of patients with prolactinomas and nonfunctional pituitary adenomas and to evaluate the impact of other pituitary hormones on their metabolic profile. ----- METHODS: Our retrospective study included 86 consecutive patients with prolactinomas and nonfunctional adenomas (29 prolactinomas and 57 adenomas). Body mass index (BMI), blood pressure, serum prolactin, growth hormone (GH), insulin-like growth factor I (IGF-I), adrenocorticotropic hormone (ACTH), cortisol, urinary free cortisol, triiodothyronine (T3), thyroxine (T4), thyroid-stimulating hormone (TSH), dehydroepiandrosterone-sulfate (DHEA-S), testosterone in men, triglycerides, total cholesterol, HDL (high-density lipoprotein) cholesterol, LDL (Low-density lipoprotein) cholesterol, alanine-transaminase, aspartate-transaminase, fasting glucose, and C-reactive protein (CRP) were obtained for all patients. Regression analyses were performed on log-transformed data. ----- RESULTS: After adjustment for age, gender, and tumor size, prolactinomas were associated with higher BMI (OR 5.61, 95%CI 1.70-9.51, p = 0.005), LDL cholesterol (OR 3.60, 95%CI 1.35-5.93, p = 0.015), DHEA-S (OR 1.97, 95%CI 1.23-3.72, p = 0.026), and lower GH levels (OR 0.43, 95%CI 0.03-0.84, p = 0.037). In a linear multivariate regression, the association between DHEA-S, GH, and prolactin remained significant even after adjustment for BMI. GH and IGF-I were associated with BMI and LDL cholesterol, but the association diminished after adjustment for serum prolactin. ----- CONCLUSIONS: Prevalence of obesity is four times higher in patients with prolactinomas than in patients with nonfunctional adenomas. Higher DHEA-S and lower GH levels in patients with prolactinomas may have an important role in prolactin-induced metabolic effects. Further studies are needed.