OBJECTIVE: Despite the increasing evidence that primary hyperparathyroidism (PHPT) contributes to greater risk of cardiovascular morbidity and mortality, its exact role in the development of cardiovascular changes and its clinical significance are still controversial. Given the multiple influence of PHPT on the cardiovascular system, this study aimed to assess the effects of PHPT on blood pressure profile, and on features of the heart and arterial vessels in normotensive symptomless patients. DESIGN: Twenty patients (8 males and 12 females) with a median age of 51.5 years (range 44 to 65 years) were evaluated and the results were compared with those of 20 controls matched for age, gender and body mass index. Patients' parathyroid hormone levels ranged from 172 to 454 pg/ml and Ca levels ranged from 11.4 to 13.5 mg/dl. Fasting levels of glucose, insulin, total and high density lipoprotein cholesterol and triglycerides were within the normal range in all subjects recruited. METHODS: Twenty-four-hour blood pressure profile, left ventricle (LV) dimension and carotid artery anatomy were investigated, the latter two by ultrasonography. RESULTS: No difference was found between the patients and controls in blood pressure profile, when the following parameters were considered: supine systolic/diastolic pressure, average 24-h systolic, diastolic and mean arterial pressure, day-time mean arterial pressure and fall in nocturnal blood pressure (-17% and -18% respectively). Heart rate and all parameters of LV mass were similar in patients and controls. The only alteration found in patients was in significantly greater carotid intimal-medial thickness (IMT) (P<0.001). Atherosclerotic plaques were more frequent in patients than in controls, with a difference reaching a trend (40% vs 10%, chi(2)=4.8; P=0.091). Considering that the carotid IMT is considered to be a marker of systemic atherosclerosis, our finding suggests early atherosclerotic changes in PHPT. No correlation was found between the severity and cardiovascular manifestation of PHPT. CONCLUSIONS: Vascular changes may occur due to a combination of structural and functional impairments in PHPT patients, likely as a result of altered calcium metabolism and impaired equilibrium of other factors regulating vascular function. Both extent and duration of PHPT can play a relative role in the development of cardiovascular complications. Considering that PHPT is now recognized as a quite common and often symptomless endocrine disorder, the evidence of cardiovascular manifestation in normotensive patients, found by this morphological study, suggests a possible implication for the management of such patients. In this light, screening for abnormalities in cardiovascular system function should be recommended in all PHPT subjects.