Urinary 6-hydroxymelatonin in menstruating women

Abstract

Melatonin is synthesized in the pineal from serotonin. A prominent diurnal rhythm in melatonin production, with peak levels occurring at night, is well documented (Tamarkin et al. 1985). Melatonin is rapidly converted and excreted in urine as conjugated Ghydroxymelatonin (6HMT). Night-time (NT) plasma melatonin levels correlate significantly with NT 6-HMT levels in urine (Lang et al. 1981), which correlate with 24-hr urinary excretion totals for 6-HMT (Lang et al. 1981; Markey et al. 1985). Urine sampling provides a noninvasive method of investigating melatonin excretion, avoiding the disruption of frequent NT plasma sampling. Psychiatric researchers have been interested in melatonin as an endogenous marker for mood disorders, especially for recurrent subtypes. BeckFriis and others (1984, 1985; Claustrat et al. 1984) have suggested that low plasma melatonin is a relatively stable marker for major depression. In view of the higher rates of certain cyclic depressions in women (cf., Parry et al. 1987), it is of interest that some dysphoric symptoms have been observed both premenstrually (American Psychiatric Association 1987) and with pharmacological doses of melatonin-for example, decreased concentration or alertness, increased sleepiness, prolonged sleep, and in depressed women, exacerbations in negative affect (cf., Cramer et al., 1974; Patkai et al. 1974; Carman et al. 1976; Lieberman et al. 1984). As depression (unipolar subtype) is encountered about twice as often in women compared with men, particularly during the reproductive years, it is important to find out whether or not melatonin production varies with the menstrual cycle.