OBJECTIVE The use of high doses of the ergot-derived dopamine agonist cabergoline (> 3 mg/day), especially with cumulative doses > 4000 mg, has been associated with an increase in cardiac valvular thickening and significant (moderate to severe) regurgitation. Whether lower doses commonly used in the treatment of prolactinomas (0.25-3 mg/week) are also associated with significant valvulopathy is controversial. The mitral valve tenting area, a subclinical index of leaflet stiffening, has also been correlated with the cumulative dose of cabergoline and severity of valvular regurgitation. METHODS We performed transthoracic echocardiography (TTE) on 50 prolactinoma patients (48% macroprolactinomas, 52% microprolactinomas, 30 male, 20 female, age 51.2 +/- 2.2 years, mean +/- SEM) who had been taking cabergoline for 6.6 +/- 0.5 years (range 1-13 years) with cumulative doses of 443 +/- 53 mg, to determine the prevalence of significant valvular thickening (> 0.5 cm) and regurgitation, and measured the mitral valve tenting area and height. The results were compared to those from age- and sex-matched controls with normal left ventricular function. RESULTS No significant valvular thickening or regurgitation of any valve was detected in the prolactinoma group and the prevalence of mild valvular regurgitation was not higher than in the case-control group. The mitral valve tenting area and height were not significantly greater than in the control group. There was no correlation between tenting area or height and cumulative cabergoline dose. CONCLUSIONS We found no evidence of increased mitral valve tenting area/height, valvular thickening or significant regurgitation with the long-term administration of the commonly used doses of cabergoline to treat prolactinoma.