Vascular reactivity in acromegalic patients: preliminary evidence for regional endothelial dysfunction and increased sympathetic vasoconstriction

BACKGROUND AND OBJECTIVES Hypertension is found in one-third of acromegalic patients. An heterogenous distribution of cardiac output has been recently demonstrated in acromegalic patients with an increased blood flow at the l evel of the upper limb, suggesting that acromegalic patients may have some degree of endothelial dysfunction. Elsewhere, studies involving hypopituita ry GH-deficient adults have shown that GH and/or IGF-I may have direct effe ct on endothelial function. SUBJECTS AND METHODS We thus compared cutaneous vasoreactivity responses in 10 normotensive patients with active acromegaly (A) (six women and four me n) aged 25-59 (mean, 43.2 years), whose basal GH and IGF-I levels ranged fr om 7.4 to 158 mU/l and from 401 to 1690 mu g/l, respectively, and in 10 nor mal age- and sex-matched controls (NC) by means of Laser Doppler flowmetry at the levels of the palm and the dorsum of the right hand. Circulatory ski n velocities were studied basally and after increasing skin temperature to 44 degrees C (in order to study direct nonspecific vasodilatation response which is independent of endothelial or autonomous nervous system and reflec ts normal vascular muscle function), after shear-stress (known to produce f low-dependent vasodilatation, mediated by nitric oxyde (NO) originating fro m endothelial cells) and after cold-stress applied on the opposite hand (kn own to produce vaso-constriction mediated by the sympathetic nervous system ). RESULTS The warm test induced a significant (P < 0.001) and similar increas e in both dorsal and palmar skin perfusion in A (mean +/- SD) (240 +/- 96 a nd 238 +/- 134%, respectively) and NC (232 +/- 137 and 233 +/- 73, respecti vely). Ischaemia release induced a significant increase in both dorsal and palmar skin blood flows in the two groups (P < 0.001), but reactivities in acromegalic patients were about one half of those measured in controls (22. 9 +/- 16.2% (A) vs. 46.9 25% (NC), 2P < 0.02, at the level of the dorsum; a nd 45.0 +/- 43.6% (A) vs. 104.7 +/- 40.1 (NC), 2P < 0.01, at the level of t he palm). Cold pressor test resulted in significant decreases in both cutan eous flows (P < 0.01) in the two groups, with a larger vasoconstriction (th at did not reach statistical significance) in acromegalic patients as compa red with controls (P < 0.10). CONCLUSION Vascular smooth cell ability to produce skin vasodilatation is n ormal but endothelium-dependent vasodilatation appears to be impaired while sympathetic-mediated vasoconstrictive response might be increased in acrom egaly. This endothelial dysfunction may contribute to hypertension and repr esent a risk factor for cardiovascular complications in acromegaly.