Endocrine Abstracts

Circadian clocks regulate the adaptation of the organism to the rotation of the earth around its axis. In mammals the circadian timing system is comprised of numerous cellular oscillators throughout the brain and the body. In the hypothalamic suprachiasmatic nucleus a circadian pacemaker is synchronized to the external light/dark cycle via direct innervation along the retinohypothalamic tract. From the SCN, peripheral clocks are synchronized by neuronal, endocrine and behavior...

Under non-stressed conditions adrenal glucocorticoid (GC) secretion shows strong circadian rhythms with blood levels peaking around wake-up time (i.e. in the morning in humans and at the beginning of the night in nocturnal rodents). These diurnal variations are primarily regulated by rhythmic activation of the hypothalamic–pituitary–adrenal (HPA) axis and the secretion of ACTH from the pituitary. While circadian HPA axis activity is ultimately controlled by the circa...