Circadian rhythm of ACTH secretion

(A) Pulse analysis of plasma ACTH concentrations in samples obtained at 10-minute intervals for 24 hours. The line represents the plasma ACTH concentration at any moment as predicted by a computer-generated deconvolution program. (B) Computer-calculated ACTH secretion rate at any moment. The circadian rhythm in plasma ACTH concentrations and, therefore, of cortisol secretion and plasma cortisol concentrations is a function of the variation in the amplitude, not the frequency, of ACTH secretory pulses. To convert pg/mL to pmol/L, multiply by 0.22.