Melatonin is known for its effects on both the sleep and reproductive system of mammals.
The latter has melatonin receptors type 1 and 2, which act to regulate, among other
things, cyclic AMP. Notwithstanding all the literature data, there is still no sound
knowledge or a clear understanding of the hormone's action on the physiology of ovarian
follicular cells.OBJECTIVE: To review and evaluate studies about melatonin action
on the ovarian granulosa/theca interna cells from the literature.METHODS: The systematic
review was carried out according to the PRISMA recommendations. The MEDLINE and Cochrane
primary databases were consulted with the use of specific terms. There was no limitation
on language or publication year.RESULTS: Seven papers about melatonin action on granulosa
cells were selected. The following can be attributed to the hormone's effects: a)
progesterone increase in culture medium; b) increased estrogen production; c) antagonistic
action on estrogen; d) improvement in cell quality resulting in improved embryo and
higher pregnancy rates; e) improved cell proliferation via MAPK; reduction of free
radicals. Nevertheless, there are contrarian papers reporting a reduction in progesterone
production.CONCLUSION: Melatonin interferes in sex steroid production, boosting progesterone
output. Such action may help improve oocyte quality.