Evidence for this role of oxytocin come from two types of experiments. First, infusion of oxytocin into the ventricles of the brain of virgin rats or non-pregnant sheep rapidly induces maternal behavior. Second, administration into the brain of antibodies that neutralize oxytocin or of oxytocin antagonists will prevent mother rats from accepting their pups. Other studies support the contention that this behavioral effect of oxytocin is broadly applicable among mammals.
Obesity. Early research suggests that taking 5-HTP might help reduce appetite, caloric intake, and weight in obese people. Other research suggests that using a specific mouth spray containing 5-HTP and other extracts (5-HTP-Nat Exts, Medestea Biotech S.p.a., Torino, Italy) for 4 weeks increases weight loss by about 41% in overweight postmenopausal women.
Melanotan II is a synthetic analogue of the α-melanocyte stimulating hormone (α-MSH). α-MSH is a melanocortin I receptor agonist which has a role in human pigmentation by stimulating production of eumelanin. Melanotan II was originally developed as a treatment for sexual dysfunction. However, the proposal was abandoned when development of the metabolite bremelanotide was established.
But Carter and other scientists are concerned by reports from the physicians and parents of children with autism spectrum disorder who say that they are already using oxytocin off-label — before it has been thoroughly tested. “We do not understand how the hormone works yet, or have enough information about what happens when it's given repeatedly,” Carter says. “This is not a molecule that people should be self-administering or playing with.”
The relationship between oxytocin and human sexual response is unclear. At least two non-controlled studies have found increases in plasma oxytocin at orgasm in both men and women. The authors of one of these studies speculated that oxytocin's effects on muscle contractibility may facilitate sperm and egg transport. Murphy et al. (1987), studying men, found that oxytocin levels were raised throughout sexual arousal and there was no acute increase at orgasm.  A more recent study of men found an increase in plasma oxytocin immediantly after orgasm, but only in a portion of their sample that did not reach statistical significance. The authors noted that these changes "may simply reflect contractile properties on reproductive tissue."
She recruited 31 men* and asked them to sniff either an oxytocin nasal spray or another spray with the same ingredients minus oxytocin – a placebo. A few weeks later, the sprays were swapped so that the men who took oxytocin now took the placebo, and vice versa. At the time, neither the scientists nor the volunteers knew which was which – that was only revealed after the experiment was over.
Oral 5-HTP results in an increase in urinary 5-HIAA, a serotonin metabolite, indicating that 5-HTP is peripherally metabolized to serotonin, which is then metabolized. This might cause a false positive test in tests looking for carcinoid syndrome. Due to the conversion of 5-HTP into serotonin by the liver, there could be a risk of heart valve disease from serotonin's effect on the heart, as based on preclinical findings. However, 5-HTP has not been associated with cardiac toxicity in humans.