An Endocrinologist's Guide to the Clock

Abstract

Research into the molecular clock provides a novel window onto endocrine and metabolic disease. These advances present new avenues for diagnostic and therapeutic strategies.

Male-female differences in 6-sulfatoxymelatonin excretion in hypopituitary patients

“…Indirectly, the clock system directs secretion through slow-wave sleep which is strongly associated with GH release, although the precise mechanism of circadian influence is not understood. There is a sexual dimorphism of plasma GH with distinct male and female patterns of growth, which may be clock-determined (1). The evaluation of 6-sulfatoxymelatonin in GH deficient adults Arch Endocrinol Metab.…”

“…2016;60/3 secretory pulses of serum melatonin during sleep might possibly allow us to elucidate these discrepancies. Such evaluation would obviously require a supplementary experimental design, including multiple blood samples all over the night in order to study melatonin nocturnal peaks (1,28).…”

“…We have demonstrated in a recent paper decreased 6-sulphatoxymelatonin (6-SM) excretion in male GH-deficient children and adolescents (11). Taking into account that there is sexual dimorphism of plasma GH with distinct male and female patterns of growth, which may be clock-determined (1), and considering that melatonin is a key hormone in the biological clock and in the day/night cycle, we decided to evaluate melatonin secretion in a group of GH-deficient male and female adults on and off replacement therapy, by measuring the excretion of its major urinary metabolite 6-SM (12,13). To evaluate possible alterations in the circadian rhythm of melatonin secretion in this group of patients, we decided to perform not only 24 hour urinary measurements, but also measurements in diurnal and nocturnal samples and to calculate nighttime-daytime delta values.…”

“…The relationships between melatonin and different pituitary hormones and sex steroids have been extensively studied; however, the relationship between growth hormone (GH) and melatonin remains unclear (1)(2)(3). Pineal gland can influence GH-IGF-1 function and, in mechanism of this dependence, changes in endogenous melatonin concentrations seem to develop an important role.…”

The role of sleep duration in diabetes and glucose control

“…Normally metabolic and physiological pathways are coordinated to this 24-h cycle by an endogenous clock enabling our bodies to coordinate appropriate physiological processes to the time of day. Research in animals and human subjects suggests that the advent of a 24/7 lifestyle that disrupts our natural sleep cycles and their alignment to the external light-dark cycle is important in the regulation of energy balance and glucose metabolism (1)(2)(3) . Sleep curtailment has become a prevalent behaviour in the Western and developing world where it is estimated that average sleep duration has declined by almost 2 h in the past 50 years (4) .…”