Effects of melatonin and estradiol on chronic pain during postmenopause

Abstract

Chronic pain is a major public health problem that affects approximately 40% of the adult population worldwide. Several epidemiological studies have shown a higher prevalence of chronic pain in women, with variations within the menstrual cycle and an increase in pain after menopause. Clinical and experimental studies have shown differences in pain perception between genders, but the underlying mechanisms of this inequality are complex and far from being understood. Estrogens play an important role in pain modulation and seem to account at least partially for these differences. Melatonin is a neurohormone synthesized mainly by the pineal gland that regulates circadian rhythms and has anti-inflammatory, antioxidant, sedative, antidepressant, anxiolytic, and analgesic effects. After menopause, melatonin levels decrease, which may be the cause of the sleep disorders that usually affect women during this period of life. Some studies have demonstrated an interaction between melatonin and estrogens in terms of antioxidant effects. The present study seeks to provide a review on melatonin, estradiol, and chronic pain in women.