Endres P, Roeren T
J Clin Endocrinol Metab. 1979 May;48(5):872-3. doi: 10.1210/jcem-48-5-872.
Plasma cAMP levels were measured using a protein-binding radioassay in nine healthy volunteer subjects over a period of 24 h under standardized conditions and also after an hour of orthostatism. No circadian variations of cAMP in plasma were observed. After orthostatism, however, there was a significant rise in cAMP concentrations.