wish i had payed better attention in Endocrinology class (Dr. H retired that year – we were his last class, & he would often fall asleep while lecturing in class – he would put the students to sleep as well). however…
i do remember that melatonin is primarily, not solely if i recall correctly, produced by the pineal gland. its production increases in response to decreased exposure to sunlight as i recall. meaning the eye’s exposure to sunlight, not the skin (don’t confuse melatonin with melanin which is a skin pigment) & is also related to one’s circadian rhythm.
as we age, we generally produce less melatonin. this makes continuous sleeping for longer periods of time a bit more difficult. i, for one, can attest to this.
melatonin has some affect on lowering BP. take too much & a very bad headache may result. had this happen once & it reminded of a similar headache i once had from taking prescription vasodilators. my guess, based upon similarity of the headache, it was very uncomfortable, that my BP was low, but I didn’t bother to measure it.
also, long term use of melatonin supplements may inhibit the body’s natural production of melatonin.
it’s prob. a good idea to only take melatonin upon your physician’s orders.