Alterations in cardiovascular autonomic function tests in idiopathic hyperhidrosis.

We performed cardiovascular autonomic function tests to assess sympathetic and parasympathetic functions in patients with idiopathic hyperhidrosis. We studied 35 patients with idiopathic hyperhidrosis and 35 age- and sex-matched controls. A thermoregulatory sweat test (TST) was performed in all subjects. Sweating was qualitatively (Minor's test at 22°C) and quantitatively (skin conductance) evaluated. Orthostatism, tilt to 65°, cold pressor test, deep breathing, Valsalva maneuver and hyperventilation were performed in patients and controls. A greater fall in blood pressure values was observed in patients than in controls in the upright tests (p<0.05). In particular, postural hypotension was present in a subgroup of patients (34%), in whom changes in lying-to-standing blood pressure and heart rate were greater (p<0.001) than those of the remaining patients. The TST revealed that the total body sweat rate (ml/cm(2)/min) was more pronounced in patients with postural hypotension (p<0.001) than in the other patients and controls. The skin conductance values of patients with postural hypotension were higher (p<0.001) than those of the remaining patients. A positive correlation was found between skin conductance values and postural hypotension. Dehydration and poor water intake may play a role in postural hypotension in patients with severe hyperhidrosis and pronounced thermoregulatory sweating. A significantly marked increase in parasympathetic function was observed in patients. Responses to deep breathing, Valsalva maneuver and hyperventilation were significantly greater in patients (p<0.001) than in controls. Idiopathic hyperhidrosis seems to be a complex dysfunction that involves autonomic pathways other than those related to sweating.