Diurnal Plasma Testosterone Rhythm and the Effect of Short-Term ACTH Administration on Plasma Testosterone in Man

In a group of 14 healthy male subjects significant diurnal cyclicity of plasma testosterone has been assessed by sampling blood either twice a day or 6 times a day. A significant decrease of plasma testosterone concentration has been observed during short-term administration of ACTH to 10 normal males. However, this seemingly significant ACTH effect could be fully explained by the diurnal rhythm in the plasma testosterone levels. In evaluating the acute effect of drug administration on the plasma testosterone level, allowance should be made for its diumal cyclicity.