Absent elevations in growth hormone, factor VIII related antigen, and plasminogen activator activity during exercise...

In cross-sectional studies elevations in growth hormone (GH), factor VIII related antigen (VIIIR:Ag), and plasminogen activator activity (PAA) have been connected with diabetic retinopathy. To evaluate the importance of these factors for the development of retinopathy, we have carried out a prospective study. In a primary study GH, VIIIR:Ag, and PAA were evaluated during a 25 min exercise test in 22 insulin dependent diabetes mellitus (IDDM) patients. After 5-7 years, the patients were re-evaluated and the presence of retinopathy in the follow-up study was correlated to the findings in the primary study. Patients with retinopathy in the primary or the second study (n = 14) showed a significant increase in GH (p less than 0.05) during the first 5 min of exercise compared with patients without retinopathy. Moreover, the 14 retinopathy patients showed further significant elevations in GH (p less than 0.001), VIIIR:Ag (p less than 0.01) and PAA (p less than 0.001) during the remaining 20 min of exercise. In contrast, patients without retinopathy (n = 8) in the follow-up study, did not show significant elevations in GH, VIIIR:Ag, and PAA during exercise. A lack of rise in GH, VIIIR:Ag, and PAA during exercise seems to indicate a resistance to retinopathy in IDDM patients.