Plasma epinephrine and norepinephrine response to stimuli in autonomic neuropathy of type 2 diabetes mellitus

Abstract

The objective of this study was to examine epinephrine and norepinephrine plasma levels in patients with clinical type 2 diabetes mellitus, at different stages of autonomic neuropathy. Eighteen patients were classified in groups without (n = 6) and with early (n = 6), definite (n = 3) and severe (n = 3) neuropathy. Blood catecholamine levels were measured after the Valsalva maneuver, cold exposure and orthostatic tests. The norepinephrine basal levels were lower in patients with severe neuropathy (0.4 ± 0.2 nmol/l), compared with the group with no neuropathy (1.3 ± 0.5 nm/l, p = 0.034), or with early neuropathy (1.3 ± 0.7 nm/l, p = 0.035). After the Valsalva maneuver, no increase was found in the group with severe alteration. In patients without neuropathy, cold exposure induced a peak of norepinephrine at 5 min (Δ = 1.9 ± 1.6 nmol/l). The increase was lower in groups with definite and severe damage. In patients with definite or moderate neuropathy, the orthostatic test induced minimal or no response. The epinephrine response to the maneuvers was not significant, and no differences were found among the groups. Norepinephrine basal levels and cold responses are diminished in patients with definite and severe autonomic neuropathy. This provides further evidence on their impaired response to stress. The comparable epinephrine levels in patients with or without autonomic neuropathy indicates that adrenal medullar function is not significantly altered.