The pineal gland releases melatonin into the blood stream in response to sympathetic noradrenergic stimulation of pinealocytes. This process is inhibited by light via the retino-hypothalamic-pineal pathway. Hence melatonin is predominantly released in darkness. Because serotonin is a precursor of melatonin, the intake of dietary tryptophan may also influence melatonin levels. Although the exact physiological role of melatonin in humans is unclear, it appears to be implicated in reproductive physiology, especially in terms of the onset of menarche. Low levels of melatonin also occur in depression. In this review, studies of melatonin in patients with anorexia nervosa and bulimia nervosa are considered in relation to potential abnormalities of noradrenergic function and circadian rhythm. The influence of weight loss, binging and purging, and depression on melatonin is discussed. Other studies involving the assessment of melatonin in relation to menstrual function are required. 0 7994 by john Wiley & Sons, lnc. Disturbances of cognition, psychological development, affect, perceptual functions including taste, hunger, and satiety, as well as neurobiological and metabolic abnormalities have all been implicated in etiological investigations of anorexia nervosa (AN) or bulimia nervosa (BN; Anderson & Kennedy, 1992). In many instances abnormalities are due to the secondary consequences of prolonged fasting and/or purging. The extent to which these abnormalities perpetuate AN and BN is unclear but is of much importance in understanding the course and outcome of these often chronic disorders.
The purpose of this paper is to: (1) selectively review the neurophysiology and functional aspects of the pineal gland and melatonin (MT) particularly in those areas that have potential relevance to AN and BN, (2) summarize what is known about MT production and release in AN and BN, and (3) discuss the potential relevance of these findings and their implications for future research.