Serum proinsulin and insulin levels were measured on 55 normal or overweight women before and after oral glucose administration. The proinsulin proportion of basal total insulin was 70% in women of normal weight. With increasing overweight the relation shifted in favour of insulin. After stimulation with glucose, proinsulin levels were significantly raised, analogous to total insulin, but les marked than the latter. The increased total insulin excretion in obesity was, therefore, largely due to insulin and less to proinsulin. The greater the overweight the later maximal insulin levels were reached after oral glucose administration: proinsulin peaks occurred later than insulin peaks. Measurement of areas from single values and corresponding times for proinsulin and insulin, after stimulation, indicated their significant correlation with the degree of overweight. In women of more than 70% overweight (Broca index), reactive proinsulin and insulin excretion decreased again despite an increase in body weight. They had a definitely reduced carbohydrate tolerance. After reduction in body weight previously increased proinsulin levels fell again. The significance of higher proinsulin levels in fasting subjects, which increased after stimulation and with overweight but were in percentage terms less than those of reactive insulin, remains unexplained.
An ivestigation has been performed in 49 women about the influence exerted on the glucose-tolerance, insulin and proinsulin secretion by hormonal contraceptives of different types and compositions. A disturbed dynamics of the insulin secretion with elevated values in the OGTT at two and three hours has been proven at a nearly equal degree using combined preparations (Anacyclin, Eugynon, Neogynon, Mikrogynon) or sequential preparations (Kombiquens, Ovanon). Though there has been interference with the glucose tolerance, the serum proinsulin in the OGTT showed increased levels too. When a combined preparation was applied, the proinsulin values were significantyl higher compared to a sequential type contraceptive. The observed disturbance of the insulin and proinsulin secretion is explained by a decreased sensitivity to insulin in the peripheral fat tissue. The actual dose of the estrogen-gestagen components has no influence on the described changes. Elevated insulin levels are demonstrable already during the first treatment cycle. The degree of the disturbance is independent of the duration of the medicamentous application during the first 6 contraceptive months. After withdrawal of the respective contraceptive steroid the insulin secretion showed nearly normal dynamics during the subseqeunt menstrual cycle.
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