[Factors affecting normal levels of insulin, cortisol, STH, thyroxine and triiodothyronine]

Published "normal" values of some hormones have an excessively wide range and unequal mean values because the material on which these values are based is from subjects suffering from different diseases which only apparently are not associated with the investigated hormone, or else the specimens are obtained under non-standard conditions (malnutrition, stress, alcohol etc.). This wide range of normal values may hide incipient pathological processes and is not suitable even as control group. The investigation is based on the assessment of insulin, growth hormone (GH), cortisol, thyroxine (T4) and triiodothyronine (T3) in a group of blood donors. The assembled results were compared with two other groups of blood donors and a group of obese subjects. The following findings were assembled: We recommend to lower the upper borderline of "normal" insulinaemia from the recommended value of 26 to 20 i.u./l, as the original range may comprise milder forms of hyperinsulinism which is recently assumed to participate in the genesis of type 2 diabetes, hypertension, coronary ischemia and polycystic ovaries. Elevated normal values of serum insulin may be obtained also from blood donors who usually have breakfast before the blood is collected. The wide range of cortisolaemia is due to the diurnal rhythm. The basal value is raised by a declining blood sugar level, alcohol, obesity and of course, varying forms of stress. The upper range of cortisolaemia at 8 a.m. should not be beyond the range of 140-690 nmol/l. GH secretion is governed by an individual 3.5-hour cycle as well as changes of the blood sugar level, e. g. during the OGTT: the declining blood sugar level raises the GH level.(ABSTRACT TRUNCATED AT 250 WORDS)