Endocrine Abstracts

Endogenous biological rhythms are commonplace throughout the natural world and can be broadly categorised as being ultradian (period <24-h), circadian (period of ~24-h), or infradian (period >24-h). Circadian rhythms have been studied in detail in mammalian species, including humans. These rhythms are driven by cell autonomous clocks found in the suprachiasmatic nuclei (SCN) of the hypothalamus and also throughout the rest of the body. Circadian clocks influence the bo...

The activity of the hypothalamic–pituitary–adrenal (HPA) axis is characterized by an ultradian (pulsatile) pattern of glucocorticoid secretion that is critical for optimal transcriptional, neuroendocrine and behavioural responses to glucocorticoids. We have investigated the molecular mechanisms underlying the origin of glucocorticoid ultradian rhythm within the rat adrenal gland. We show that this rhythm of glucocorticoids depends on highly dynamic processes within a...

Changes in hormone output to regulate physiological processes is a feature of all endocrine systems, with the added complication that for many systems, the pattern as well as level of output, determines the response of target tissues. Periodic patterns of hormone secretion can occur over multiple time scales, from ultradian to circadian, infradian, and circannual and may be dependent on physiological status. The activity and output of lactotroph and somatotroph cells of the pi...