Problems in standardization of digitalis-like substance assays by means of competitive immunological methods.

340 CLINICALCHEMISTRY. Vol. 33, No. 2, 1987 parathyroid gland, medullothyroid gland, and pancreas f3 cells), l,25-dihydroxyvitamin D, and enzymes are involved (3,4). Moreover, arteriosclerosis and atherosclerosis are calcium-dependent (3, 5). In IDD women, the significant negative correlation between P1Ca and total cholesterol might be accounted for by the internalization of the calcium or even the cholesterol in the artery wall at a younger age, depending on whether cholesterol or calcium increased in their plasma. Thus, an increase in plasma cholesterol could allow P1-Ca to penetrate into the artery intima, to form atherosclerotic plaques in patients for whom atherosclerosis is very common and occurs early (4). The Bogalusa Heart Study (Framingham Junior survey) has just provided additional proof that cholesterol is one, if not the major, cause of atherosclerosis (6). Could calcium be the missing piece in this puzale of atherosclerotic plaque formation? Once again, biological results are not the same for both sexes (2-4). The epidemiologic, clinical, ergometric, and therapeutic particularities of women presenting with coronary insufficiency have just been described (7). Our results raise questions that were not resolved in that study, and suggest that much work remains to be done.