Looks like I left a lot out.
Intentionally,...
After all, tis just a forum.
Liver:- It produces Vit B3 & l-Tryptophan & l-Taurine
Some people don't manufacture enough and it's either genetic along a same sex line (aka agnate) or it's farked up after using certain recreational drugs.
Brain Stem > Circle of Willis:- Here, the l-Tryptophan is converted to 5HTP and then Serotonin. Vit B3 helps the Serotonin to be utilised better.
Pineal Gland:- Excess Serotonin gathers here. Taurine gathers here. Collectively, they form Melatonin. Melatonin is formed to some degree in daylight. Then it's released after sundown. When released, one feels sleepy > throughout the night it helps circadian rhythms and REM.
Supplements:- If your same sex parent has had sleep problems or if you've farked with drugs, Melatonin can be obtained as 5mg lozenges that you suck before bed.
Better still, get a HOD Test (Uni Saskatchewan Inventory) done to see how short you might be of Serotonin. Serotonin deficiencies cannot be tested by scans/blood/urine/hair. If your mind races before going off to sleep, you're likely to be short of B3 & l-Tryptophan > Serotonin > Melatonin.
GL