That the islet tissue is not uniform in its make-up and hence may show variation in its ability to produce insulin is indicated by the varying percentages of the three types of cells: A cells, 10 -40%, B cells, 60-90%, D cells, 2-8%.
The obvious interpretation of these facts is that, although every individual is born with the anatomical and physiological machinery for producing insulin, the potential rates of production probably vary through a 10-fold or greater range. In some diabetics, for instance, the insulin-producing capacity becomes a limiting factor early in life; in others the machinery may limp along, and diabetes may not appear until the individuals become adults; in still others the individuals may be non-diabetic through middle age only to have the deficiency show up when the aging process is well along. Some individuals probably have throughout life the capacity for producing just about the right amount of insulin; in others the tendency may be to product too much with a resulting hyperinsulinism which may be mild or severe. The existence of this enormous graduation in the capability for producing insulin – which may, of course, be modified by various environmental influences and particularly aging- seems to square with all the known facts. The fact that some chronically thin people hae been successfully treated with insulin so that they have gained weight (fat deposits) suggest that these individuals may tend to be deficient in insulin production. It is well known, however, that obesity and diabetes are often associated with each other, and this association is in line with the conclusion that diabetes may have several etiologies depending upon the endocrine pattern of the individual who be comes afflicted.
This discussion should not imply that the problem of diabetes revolves wholly around the ability to produce insulin. There is evidence that such other organs of the body as the pituitary, the thyroids, the adrenals, and the liver all have their effects on carbohydrate metabolism and influence the prevention, onset and progress of diabetes.