Reduced microvascular perfusion and reactivity in adult GH deficient patients is restored by GH replacement.

BACKGROUND

An increased cardiovascular risk and mortality in hypopituitary patients receiving conventional hormonal treatment without GH replacement have been shown in several studies. Various atherogenic risk factors including endothelial dysfunction - an early event in the atherogenesis - are more expressed in adults with GH-deficiency (GHD). Changes in microcirculation and vascular reactivity could represent an early marker of developing vascular changes.

OBJECTIVE

To evaluate the microcirculation and vascular reactivity in a GHD state before and during GH replacement. SUBJECTS, METHODS AND DESIGN: Thirteen adult patients (ten men, mean age 40+/-9 years) with severe GHD were studied. The skin microvascular perfusion and reactivity were measured by laser-Doppler flowmetry on the forearm. Two dynamic tests for vascular perfusion and reactivity were used - postocclusive reactive hyperemia (PORH) and thermal hyperemia (TH) at 44 degrees C. Measurements were performed before and after 6 and 12 months on GH replacement with a dose of GH that normalized IGF-I serum levels. The parameters of tissue perfusion and vascular reactivity measured in GHD were compared with values during GH treatment and with the results of the control group.

RESULTS

Peak flow during TH in GHD patients was significantly reduced before GH treatment when compared with healthy subjects (means+/-s.e.m., 68+/-6.6 vs 111+/-8.3 perfusion units (PU), P<0.001) and normalized on GH treatment (109+/-12.7 PU). The velocity of perfusion increase during TH before treatment was significantly reduced in GHD as well (0.84+/-0.07 vs 1.53+/-0.19 PU/s, P<0.03) and normalized on GH treatment (1.38+/-0.24 PU/s). The PORH was also significantly reduced in GHD compared with controls (PORH(max) 414+/-63 vs 528+/-58%, P<0.05) and during GH treatment was restored to values not different from controls (642+/-86%, P=NS).

CONCLUSIONS

Skin microcirculation and vascular reactivity measured by laser-Doppler flowmetry is significantly reduced in GHD adults and is restored during GH replacement therapy. Reduced tissue perfusion and reactivity probably reflect the endothelial dysfunction in the GHD state. Reduced nitric oxide production and bioavailability and also other factors like increased sympathetic activity and reduced conversion of thyroxine to triiodothyronine in the GHD state can contribute to changes in microcirculation. Restoration of vascular reactivity by GH replacement might have favorable clinical consequences on the increased vascular morbidity of GHD patients. Reduced skin microvascular perfusion and reactivity in GHD probably contribute to the impaired thermoregulation - a clinical symptom of GHD.