title: An endocrinologist's guide to the clock.
abstract: BACKGROUND
  It has long been recognized that a "biological clock" residing in the suprachiasmatic nucleus controls circadian or daily variations in physiological processes. Old observations are now being revisited after the discovery of the cellular mechanism of timekeeping, the molecular clock, an autoregulatory feedback loop of transcription factors that cycles over a period of approximately 24 h. Its functioning or breakdown impinges upon the physiology and pathophysiology of numerous systems, including the endocrine system and metabolism. Here we provide an introduction to those aspects of the clock most relevant to the endocrinologist.
  
  
  METHODS
  Articles were identified by searching PubMed using the search terms "circadian" and "clock" and refining results to include articles relating to endocrinology and metabolism.
  
  
  RESULTS
  We discuss current understanding of the mechanisms through which hormonal and metabolic axes fall under the influence of the circadian clock. Of particular interest is the complex interaction of genetic and environmental factors in determining health or disease states.
  
  
  CONCLUSIONS
  Research into the molecular clock provides a novel window onto endocrine and metabolic disease. These advances present new avenues for diagnostic and therapeutic strategies.
authors.affiliation: Division of Cardiovascular and Diabetes Research, LIGHT Laboratories, University of Leeds, Clarendon Way, Leeds LS2 9JT, United Kingdom.
authors.forename: Madhu J
authors.initials: MJ
authors.lastname: Prasai
authors.forename: Ida
authors.initials: I
authors.lastname: Pernicova
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Grant
authors.forename: Eleanor M
authors.initials: EM
authors.lastname: Scott
mesh_terms: D000818:Animals; D001683:Biological Clocks / Q000502:physiology*; D021081:Chronobiology Disorders / Q000150:complications; D004700:Endocrine System Diseases / Q000175:diagnosis / Q000209:etiology* / Q000378:metabolism / Q000628:therapy; D004704:Endocrinology / Q000639:trends*; D017408:Guidelines as Topic; D006728:Hormones / Q000494:pharmacology / Q000502:physiology; D006801:Humans; D008659:Metabolic Diseases / Q000175:diagnosis / Q000209:etiology* / Q000378:metabolism / Q000628:therapy; D008954:Models, Biological
chemical_list: D006728:Hormones